Category: MCQ

Acids, Bases and Salts Class 10 MCQs Questions with Answers

Question 1.
What happens when the solution of an acid is mixed the solution of a base in a test tube?
(I) The temperature of the solution increases
(II) The temperature of the solution decreases
(III) The temperature of the solution remains the same
(IV) Salt formation takes place
(a) Only (I)
(b) (I) and (III)
(c) (I) and (III)
(d) (I) and (IV)
Answer:
(d) (I) and (IV)

Explanation: When an acid reacts with a base, a neutral salt is formed by the neutralisation process. As the neutralisation process is an exothermic reaction, the temperature of the solution increases.
Acid + Base → Salt + Water

Question 2.
If 10 mL of H₂SO₄ is mixed with 10 mL of Mg(OH)₂ of the same concentration, the resultant solution will give the following colour with a universal indicator:
(a) Red
(b) Yellow
(c) Green
(d) Blue
Answer:
(c) Green.
Explanation: If 10 mL of H₂SO₄ is mixed with 10 mL of Mg(OH)₂ of the same concentration, the resultant solution be MgS04 which is a neutral salt and universal indicator will give the green colour in this solution:

Related Theory:
When an acid reacts with a base it forms salt and water. As a result, acidic properties disappear The process is called neutralisation. For a neutral solution. pH is 7. The solution having pH 7 wilL turn green in colour in universal indicator.

Question 3.
Which of the following saLts does not contain water of crystatUsatlon?
(a) Blue vitriol
(b) Baking soda
(c) Washing soda
(d) Gypsum
Answer:

Question 4.
A visually challenged student, has to perform a lab test to detect the presence of acid in a given solution. The acid-base indicator preferred by him will be:
(a) Blue litmus
(b) Clove oil
(c) Red cabbage extract
(d) Hibiscus extract
Answer:
(b) Clove oil
Explanation: Clove oil is an olfactory indicator. These are the substances which give one type of odour in acidic medium so a visually challenged student prefers to use clove oil as an acid-base indicator.

As in basic solutions, the smell of clove oil disappears while the smell is retained when mixed with an acid, on the other hand, blue litmus, red cabbage extract and hibiscus extract wouLd not be used as acid-base indicator because in these indicators there will be a change in the colour.

Question 5.
Baking soda is a mixture of:
(a) Sodium carbonate and acetic acid
(b) Sodium carbonate and tartaric acid
(c) Sodium hydrogen carbonate and tartaric acid
(d) Sodium hydrogen carbonate and acetic acid
Answer:

Question 6.
Which of the following gives the correct increasing order of acid strength?
(a) Water < acetic acid < hydrochloric acid
(b) Water < hydrochloric acid < acetic acid
(c) Acetic acid < water < hydrochloric acid
(d) Hydrochloric acid < water < acetic acid
Answer:

Question 7.
What is observed when we pour a drop of acetic acid first on red and then on blue litmus papers?
(a) Red litmus paper becomes colourless and blue litmus paper remains blue.
(b) Red litmus paper turns blue and blue litmus paper remains blue.
(c) Red litmus paper remains red and blue litmus paper turns red.
(d) Red litmus paper turns blue and blue litmus paper turns red.
Answer:

Question 8.
Sodium hydrogen carbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?
(I) It turns lime water milky.
(II) It extinguishes a burning splinter.
(III) It dissolves in a solution of sodium hydroxide.
(IV) It has a pungent odour.
(a) (I) and (II)
(b) (I), (II) and (III)
(c) (II), (III) and (IV)
(d) (I) and (IV)
Answer:
(b) (I), (II) and (III)

Explanation: Reaction of sodium hydrogen carbonate with acetic acid forms sodium acetate and water with carbon dioxide (CO₂) gas.

CO₂ does not have a pungent smell but it shows all the other three properties:

1. turns lime water milky,
2. is a non-supporter of combustion and
3. absorbed by strong alkalis such as NaOH.

Question 9.
Common salt besides being used in the kitchen can also be used as the raw material for making:
(I) Washing soda
(II) Bleaching powder
(III) Baking soda
(IV)Slaked Urne
(a) (I) and (II)
(b) (I), (II) and (IV)
(c) (I) and (III)
(d) (I), (III) and (IV)
Answer:

Question 10.
To protect tooth decay we are advised to brush our teeth regularly. The nature of the toothpaste commonly used ¡s:
(a) Acidic
(b) Neutral
(c) Basic
(d) Corrosive
Answer:
(c) Basic

Explanation: The toothpaste commonly used is alkaline or basic in nature as they contain mild bases such as sodium fluoride or sodium bicarbonate in their composition.

The base reacts with the acid formed during bacterial action in the mouth and neutralises its bad effects. Thus, preventing tooth decay. So, they can neutralize the effect of extra acids being formed in the mouth cavity which are mainly responsible for tooth decay.

Related Theory
When we eat sweet things, the pH of our mouth falls below 5.5 (moderately acidic) as the oral bacteria release acid while acting on sugars present in our food. The acidic conditions are capable of corroding the enamel which is made up of calcium phosphate. This causes the tooth to decay.

Question 11.
Match the chemical substances given in Column I with their appropriate application given in Column II:

Column I	Column II
(A) Bleaching Powder	(1) Preparation of glass
(B) Baking Soda	(2) Production of H2 and Cl2
(C) Washing Soda	(3) Decolourisation
(D) Sodium Chloride	(4) Antacid

Answer:

Question 12.
Which of the following phenomena occur, when a small amount of acid is added to water?
(I) Ionisation
(II) Neutralisation
(III) Dilution
(IV)Salt formation
(a) (I) and (II)
(c) (II) and (III)
(b) (I) and (III)
(d) (II) and (IV)
Answer:

Question 10.
To protect against tooth decay we are advised to brush our teeth regularly. The nature of the toothpaste commonly used is:
(a) Acidic
(b) Neutral
(c) Basic
(d) Corrosive
Answer:
(c) Basic

Explanation: The toothpaste commonly used is alkaline or basic in nature as they contain

Question 13.
A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue:
(a) Lemon juice
(b) Vinegar
(c) Common salt
(d) An antacid
Answer:
(d) An antacid

Explanation: pH paper gives greenish-blue colour in a weak alkaline medium so antacid [Mg(OH)₂] which is an alkaline compound will show greenish-blue color on pH paper.

Related Theory
Lemon fruit contains citric acid, vinegar has acetic acid and common salt is the neutral salt the clear super natant solution turns the pH paper yellowish-orange means the given sample of soil is acidic so it can be neutralised by base/alkaline solution.

Question 14.
Which of the following is not a mineral acid?
(a) Hydrochloric acid
(b) Citric acid
(c) Sulphuric acid
(d) Nitric acid
Answer:

Question 15.
Which of the following is/are true when HCl_(g) is passed through water?
(I) It does not ionise in the solution as it is a covalent compound.
(II) It ionises in the solution.
(III) It gives both hydrogen and hydroxyl ions in the solution.
(IV) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule.
(a) Only (I)
(b) Only (III)
(c) (II) and (IV)
(d) (III) and (IV)
Answer:
(c) (II) and (IV)

Explanation: HCl, is a polar covalent compound, easily ionises in water to form hydronium (H₃O⁺) and chloride ions (Cl^–). HCl (a strong acid) ionises completely in water to produce H⁺ and Cl^– ions. H⁺ ion combines with water molecules to produce hydronium ions.

Question 16.
Which among the following is not a base?
(a) NaOH
(b) KOH
(c) NH₄OH
(d) C₂H₅OH
Answer:
(d) C₂HsOH
Explanation: C₂H₅OH is not a base. C₂H₅OH is an organic compound with -OH functional group that is known as alcohol. It cannot give OH^– ions in its solution. It cannot dissociate ions in a solution. Thus, it cannot be a basic compound.

Question 17.
Identify the correct representation of reaction occurring during the chloralkali process.
(a) 2NaCl_(l) + 2H₂O_(l) → 2NaOH_(l) + Cl_2(g) + H_2(g)
(b) 2NaCl_(l) + 2H₂O_(aq) → 2NaOH_(aq) + Cl_2(g) + H_2(aq)
(c) 2NaCl_(aq) + 2H₂O_(l) → 2NaOH_(aq) + Cl_2(aq) + H_2(aq)
(d) 2NaCl_(aq) + 2H₂O_(l) → 2NaOH_(aq) + Cl_2(g) + H_2(g)
Answer:

Question 18.
Which of the following statements is true for acids?
(a) Bitter and change red litmus to blue.
(b) Sour and change red litmus to blue.
(c) Sour and change blue litmus to red.
(d) Bitter and change blue litmus to red.

Question 19.
Zinc granules on treating with an acid X, form zinc sulphate (ZnSO₄) salt along with the evolution of a gas Y, which burns with a pop sound when brought near to a burning candle. Identify acid X and gas evolved Y.
(a) X-sulphuric acid and Y-oxygen gas
(b) X-hydrochloric acid and Y-oxygen gas
(c) X-sulphuric acid and Y-hydrogen gas
(d) X-hydrochloric acid and Y-hydrogen gas [Diksha]
Answer:
(c) X-sulphuric acid and Y-hydrogen gas

Explanation: When an acid reacts with a metal, hydrogen gas is liberated. In the given reaction, when dilute sulphuric acid reacts with zinc granules, hydrogen gas is liberated and zinc sulphate solution is formed:

The presence of hydrogen gas is tested by bringing a lighted candle near it. When a lighted candle is brought near the test tube containing hydrogen gas, it burns with a ‘pop’ sound making a little explosion.

Hence, acid X is sulphuric acid and gas Y is hydrogen gas.

Question 20.
Which of the following solutions in water does not conduct electricity?
(a) Hydrochloric acid
(b) Sodium chloride
(c) Glucose
(d) Sulphuric acid [Diksha]
Answer:
(c) Glucose

Explanation: The aqueous solution of an acid conducts electricity because of the presence of charged particles called ‘ions’ in it. When hydrochloric acid (HCl) is dissolved in water, its aqueous solution contains hydrogen ions (H⁺) and chloride ions (Cl^–). These ions carry electric currents. So, due to the presence of H⁺ and Cl^– ions, a solution of hydrochloric acid conducts electricity.

On the other hand, the hydrogen-containing compound such as glucose is not categorized as acid because it does not produce hydrogen ions or some other ions when dissolved in water and hence does not conduct electricity. Therefore, the answer is glucose.

Question 21.
Which of the following will turn phenolphthalein pink?
(a) NaOH_(aq)
(b) HCl_(aq)
(c) CH₃COOH_(aq)
(d) H₂O [Diksha]
Answer:

Question 22.
Which one of the following is not a use of washing soda:
(a) Sodium carbonate (washing soda) is used in glass, soap and paper industries.
(b) It is used in the manufacture of sodium compounds such as borax.
(c) Sodium carbonate can be used as a clean¬ing agent for domestic purposes.
(d) It is used for disinfecting water.
Answer:
(d) It is used for disinfecting water.

Explanation: The compound that is used for disinfecting water is bleaching powder. How¬ever, washing soda is used for removing the permanent hardness of water.

Question 23.
The approximate pH values of four salts is given below. Select the row(s) containing the correct information.

Name of Salt	PH
(I) Potassium Sulphate	10
(II) Ammonium nitrate	5
(III) Sodium acetate	3
(IV) Sodium hydrogen carbonate	8

(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (II) and (IV)
Answer:

Question 24.
Zinc granules on treating with a substance X, form a salt sodium zincate along with the evolution of a gas Y which burns with a pop sound when brought near a burning candle. Identify the substance X and gas evolved Y.

X	Y
(a) Acetic acid	Hydrogen
(b) Sodium hydroxide	Hydrogen
(c) Sodium hydroxide	Oxygen
(d) Zinc hydroxide	Hydrogen

Answer:
(b) X is Sodium hydroxide and Y is hydrogen.

Explanation: When zinc granules react with sodium hydroxide, salt sodium zincate is formed along with hydrogen gas, which burns with a pop sound.

The equation of the reaction taking place is:
2NaOH_(aq) + Zn(s) → Na₂ZnO_2(aq) + H_2(g)

Question 25.
Which of the following salts belong to the same family of salts?
(I) sodium chloride and sodium acetate
(II) calcium sulphate, magnesium sulphate
(III) sodium carbonate and sodium hydrogen -carbonate
(IV) sodium chloride and magnesium sulphate
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) (I), (II) and (III)
(d) (I), (III) and (IV)
Answer:

Question 26.
A student noted his observations regarding the acidic or basic nature of salts as below:
(I) Sodium chloride is a neutral salt
(II) Ammonium chloride is a basic salt
(III) Sodium carbonate is a neutral salt
(IV) Copper sulphate is an acidic salt Select the incorrect observations:
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
Answer:
(b) Both (II) and (III)

Explanation: The salts of strong acids and strong bases give neutral solutions. Therefore, sodium chloride is a neutral salt as it is obtained from sodium hydroxide (a strong base) and hydrochloric acid (a strong acid).

The salts of strong acids and weak bases give acidic solutions. Therefore, ammonium chloride and copper sulphate are acidic salts as ammonium chloride is obtained from ammonium hydroxide (a weak base) and hydrochloric acid (a strong acid), and copper sulphate is obtained from copper hydroxide (a weak base) and sulphuric acid (a strong acid).

The salts of weak acids and strong bases give basic solutions. Therefore, sodium carbonate is a basic salt as it is obtained from carbonic acid (a weak acid) and sodium hydroxide(a strong base).

Assertion Reasoning questions Class 10 Science Chapter 2

For the following questions, two statements are given – one labelled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 27.
Assertion,(A): HCl gas does not change the colour of dry blue litmus paper.
Reason (R): Acids always produce hydrogen ions.
Answer:
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the (A).

Explanation: HCl gas does not change the colour of dry litmus paper but changes colour of moist litmus paper as acids produce hydrogen ions only in solution.

Question 28.
Assertion (A): Generally, the colour of indicators changes in particular pH range.
Reason (R): Indicators are weak acids or weak base and exhibit different colours in molecular form and ionic form.
Answer:
(a) (A) and (R) are true and (R) is the correct explanation of the (A).

Explanation: Since indicators are weak acids or weak bases, their percentage of existence in molecular state and in ionized state depends on the strength of acidic/basic/neutral solution to which they are added. Hence their colours change at a particular pH range.

Question 29.
Assertion (A): Zinc reacts with sodium hydroxide solution and hydrogen gas is evolved.
Reason (R): All metals react with bases to evolve hydrogen gas.

Question 30.
Assertion (A): While diluting an acid, water is slowly added to acid with constant stirring.
Reason (R): The process of dissolving an acid in water is a highly exothermic reaction.

Question 31.
Assertion (A): Metal oxides are acidic in nature.
Reason (R): Calcium hydroxide reacts with carbon dioxide to form a salt and water.
Answer:
(d) (A) is false, but (R) is true.

Explanation: The reaction of calcium hydroxide with carbon dioxide to form a salt and water is similar to the reaction between an acid and a base. Therefore, non-metal oxides are acidic in nature.

Question 32.
Assertion (A): When copper sulphate crystals are heated in a dry boiling tube, they turn white.
Reason (R): Water of crystallization is the number of water molecules present in one formula unit of a salt.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).

Explanation: Copper sulphate crystals that seem to be dry contain water of crystallisation. When we heat the crystals, this water is removed and the salt turns white.
CUSO₄.5H₂O → CuSO₄ + 5H₂O

Question 33.
Assertion (A): When copper oxide is added to dilute hydrochloric acid, the colour of the solution becomes blue-green.
Reason (R): Copper (II) chloride is formed.
Answer:
(a) (A) and (R) are true and (R) is the correct explanation of the (A).

Explanation: When copper oxide is added to dilute hydrochloric acid, the colour of the solution becomes blue-green due to the formation of Copper (II) chloride, which is blue-green in colour.

MCQ Questions for Class 10 Science with Answers

Carbon and Its Compounds Class 10 MCQs Questions with Answers

Question 1.
Carbon exists in the atmosphere in the form of:
(a) Only carbon monoxide
(b) Carbon monoxide in traces and carbon dioxide
(c) Only carbon dioxide
(d) Coal [NCERT Examplar]
Answer:
(b) Carbon monoxide in traces and carbon dioxide

Explanation: Only 0.03% of atmospheric air contatins carbon in the form of carbon dioxide. The natural concentration of carbon monoxide in the air is around 0.2 parts per million (ppm). It is produced by the incomplete combustion of carbon due to a limited supply of oxygen. It is a pollutant which is formed when hydrocarbons such as petrol and diesel are burnt. Carbon monoxide (CO) is short-lived and gets oxidised into carbon dioxide (CO₂).

Related Theory
Carbon also occurs in the form of minerals such as carbonates, fossil fuels and other organic compounds.

Question 2.
A molecule of ammonia (NH₃) has:
(a) Only single bonds
(b) Only double bonds
(c) Only triple bonds
(d) Two double bonds and one single bond
Answer:

Question 3.
Buckminster fullerene is an allotropic form of:
(a) Phosphorus
(b) Sulphur
(c) Carbon
(d) Tin
Answer:
(c) Carbon

Explanation: Buckminsterfullerene is an allotrope of carbon with 60 carbon atoms, which are arranged in the shape of a football. Since this also looks like the geodesic dome designed by the US architect Buckminster Fuller, the molecule was named fullerene.

Question 4.
Which of the following is the correct representation of electron dot structure of nitrogen molecule?

Question 5.
The correct electron dot structure of a water molecule is:

Answer:

Explanation: In a water molecule, the center oxygen atom contains two lone pairs of electrons and forms two single covalent bonds with two hydrogen atoms.

Oxygen (O) has 6 valence electrons and hydrogen (H) has 1.

All the 8 electrons must be arranged in pairs so that oxygen completes the octet structure (8 electrons in its valence cell). Each hydrogen atom has now 2 electrons in its valence shell.

Question 6.
Which of the following does not belong to the same homologous series?
(a) CH₄
(b) C₂H₂
(c) C₃H₈
(d) C₄H₈
Answer:
(d) C₄H₈

Explanation: Methane (CH₄) is the first member of the homologous series of alkanes. Successive members of the same homologous series differ by -CH₂ unit.

Second member is ethane (C₂H₂) and the third member is propane (C₃H₈). The fourth member should be butane (C₄H₁₀).

Hence, C₄H₈ does not belong to the homologous series of alkanes.

CH₄, C₂H₆, C₃H₃ belong to the same series that is of alkane and differ by -CH₂ unit but C₄H₈ does not belong to alkanes.

Question 7.

In the above-given reaction, alkaline KMn04 acts as:
(a) Reducing agent
(b) Oxidising agent
(c) Catalyst
(d) Dehydrating agent
Answer:

Question 8.
In which of the following compounds is -OH the fi.ånctionoL group?
(a) Butanone
(b) Butanot
(c) Butanoic
(d) Butanat
Answer:

Question 9.
Structural the formula of ethyne is:

Answer:

Question 10.
Identify the unsaturated compounds from the following:
(I) Propane
(II) Propene
(III) Propyne
(IV)Chloropropane
(a) (I) and (II)
(b) (II) and (IV)
(c) (III) and (IV)
(d) (II) and (ill)
Answer:
(d) (II) and (III)

Explanation: Alkene and alkyne are unsaturated hydrocarbons as they have double and triple covalent bonds between carbon atoms. Alkanes such as propane are saturated hydrocarbons.

Propane and chloropropane are saturated hydrocarbons that contain only single bonds.

Related Theory:
A hydrocarbon in which two carbon atoms are connected by a ‘double bond’ or a ‘triple bond’ is called an unsaturated hydrocarbon.

Question 11.
Chlorine reacts with saturated hydrocarbons at room temperature in the:
(a) absence of sunlight
(b) presence of sunlight
(c) presence of water
(d) presence of hydrochloric acid
Answer:

Question 12.
In the soap micelles
(A) The ionic end of soap ¡s on the surface of the cluster, white the carbon chain is in the interior of the cLuster.
(B) The ionic end of soap is in the interior of the cluster and the carbon chain is out of the cluster.
(C) Both the ionic end and carbon chain are in the interior of the cluster.
(D) Both the ionic end and carbon chain are on the exterior of the cluster.
Answer:
(a) The ionic end of soap ¡s on the surface of the cluster, while the carbon chain is in the interior of the cluster.

ExpLanation: The soap molecule has a hydrophilic head and a hydrophobic tail. When soap is mixed into the water, the soap molecules arrange themselves into tiny clusters called ‘micelles’. The hydrophilic parts of the soap (water-Loving) molecules point outwards, forming the outer surface of the micelle. The hydrophobic part (oil-loving) group together and point towards the inner side. Micelles can trap fats in the center and help to get rid of oil and dirt.

Question 13.
The structura[formuta of benzene is:

Question 14.
Ethanol reacts with sodium and forms two products. These are:
(a) Sodium ethanoate and hydrogen
(b) Sodium ethanoate and oxygen
(c) Sodium ethoxide and hydrogen
(d) Sodium ethoxide and oxygen
Answer:
(c) Sodium ethoxide and hydrogen

Explanation: Ethanol (C₂H₅OH) reacts with sodium to form sodium ethoxide (C₂H₅ONO) along with the Liberation of hydrogen gas.

2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

Question 15.
The correct structural formula of butanoic acid is;

Answer:

Question 16.
Mineral acids are stronger acids than carboxylic acids because:
(I) Mineral acids are completely ionized.
(II) Carboxylic acids are completely ionized.
(III) Mineral acids are partially ionized.
(IV) Carboxylic acids are partially ionized.
(a) (I) and (IV)
(b) (II) and (III)
(c) (I) and (II)
(d) (III) and (IV)
Answer:

Question 17.
Which of the following is not a straight-chain hydrocarbon?

Answer:

Explanation: In structures (1), (2), and (3), all the carbon atoms are attached by covalent bonds in a continuous straight chain.

In structure (4), the -CH 3 group is attached to the second carbon atom of the chain forming a branch. Hence, a compound in structure (iv) is a branched-chain hydrocarbon.

Related Theory
A branch-chain hydrocarbon contains some side chains which are bonded with the parent carbon chain.

Question 18.
Which among the following are unsaturated hydrocarbons?

(a) (I) and (III)
(b) (II) and (III)
(c) (II) and (IV)
(d) (III) and (IV)
Answer:
(c) (II) and (IV)

Explanation: Unsaturated hydrocarbons are organic compounds that consist of a double or a triple bond between two adjacent carbon atoms. The hydrocarbons having at least one double bond between two adjacent carbon atoms are called alkenes, whereas the hydro¬carbons which contain a carbon-carbon triple bond are referred to as alkynes. Both (II) and (IV) structures have double or triple carbon-carbon bonds respectively.

Question 19.
The name of the compound, CH₃—CH₂— CHO is:
(a) Propanol
(b) Propanone
(c) Ethanol
(d) Ethanal
Answer:

Question 20.
Which of the following represents saponification reaction?

Answer:

Question 21.
A student takes about 4 mL of distilled water in four test tubes marked P, Q, R, and S. He then dissolves in each test tube an equal amount of one salt in one test tube, namely sodium sulfate in P, potassium sulfate in Q, calcium sulfate in R and magnesium sulfate in S. After that he adds an equal amount of soap solution in each test tube. On shaking each of these test tubes well, he observes a good amount of lather (foam) in the test tubes marked:
(a) P and Q
(b) Q and R
(c) P, Q and S
(d)P, Rand S
Answer:

Question 22.
Consider the following oils:
(I) Mobil oil
(II) Castor oil
(III) Turpentine oil
(IV) Kerosene
(V) Mustard oil
(VI) Coconut oil
Which of these can be used for the preparation of soap?
(a) I, II, III, VI
(b) M, V, VI
(c) II, III, V, VI
(d) II, III, VI
Answer:
(b) II, V, VI (Mustard oil, castor oil, coconut oil)

Related Theory
Oil in soaps used to moisturizes the skin and creates creamy lather.

Question 23.
A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best wben he uses water obtained from:
(a) rain
(b) tap
(c) hand pump
(d) pond
Answer:

Question 24.
You have four test tubes, A, B, C, and D containing sodium carbonate, sodium chloride, lime water and blue litmus solutions respectively. Out of these the material of which test tube/test tubes would be suitable for the correct test of acetic/ ethanoic acid?
(a) only A
(b) A and B
(c) B and C
(d) A and D
Answer:

Question 25.
A student took four test tubes P, Q, R, and S and filled about 8 mL of distilled water in each. After that he dissolved an equal amount of Na₂SO₄ in P, K₂SO₄ in Q, CaSO₄ in R, and MgSO₄ in S. On adding an equal amount of soap solution and shaking each test tube well, a good amount of lather will be obtained in the test tubes:
(a) P and Q
(b) P and R
(c) P, Q, and S
(d) Q, R, and S
Answer:

Question 26.
A student wants to prepare soap in the laboratory. Which of the following sets of materials he should use?
(a) Neem oil and NaCl
(b) Neem oil and Na₂CO₃
(c) Mustard oil and NaOH
(d) Mineral oil and NaOH
Answer:

Question 27.
You have neem oil in a beaker. In order to study saponification reaction, which of the following chemical substances would you add to this oil?
(a) 20% Ca(OH)₂
(b) 20% NaOH
(c) 30% Mg(OH)₂
(d) 10% Ca(OH)₂
Answer:
(b) 20% NaOH

Explanation: Oil or fat when treated with sodium hydroxide solution, gets converted into sodium salt of fatty acid (soap) and glycerol.

fat + NaOH → glycerol + sodium salt of fatty acid

In options (a) and (d) the base used is Ca(OH)₂ whereas in option (c), the base used is 30 % Mg(OH)₂.
Therefore, the correct option is (b) as it uses 20% NaOH,

Question 28.
If you take some distilled water in a test- tube, add an equal amount of acetic acid to it, shake the test tube well and leave it undisturbed on the test tube stand, then after about 5 minutes, what would you observe?
(a) There is a Layer of water over the layer of acetic acid.
(b) A precipitate is settling at the bottom of the test tube.
(c) Bubbles of colorless gas are coming out of the test tube.
(d) There is a clear, colorless transparent solution in the test tube.
Answer:
(d) There is a dear, colorless transparent solution in the test tube.

Explanation: Acetic Acid is miscible in water and therefore when acetic acid is added to water it dissolves readily in water forming a homogeneous solution.

Question 29.
Soaps are formed by alkaline hydrolysis of:
(a) Inorganic salts
(b) Carboxylic acids
(c) Esters of long-chain fatty acids
(d) Esters of small chain fatty acids
Answer:

Question 30.
In the preparation of soap addition of sodium chloride causes:
(a) Complete saponification
(b) Complete hydrolysis
(c) Complete precipitation
(d) Complete neutralization
Answer:
(c) Complete precipitation

Related Theory
The soap is formed by the precipitation by the common salt (NaCl). When the salt is added in the aqueous solution then the reaction occurs and the soap is precipitate out from the solution. When the soap is added to the solution then the solubility of the soap became decreases and the soap precipitates out from the solution as a solid form of the soap.

Question 31.
A student is given equal amount of three samples of water with temporary hardness labeled as ‘A’, ‘B’ and ‘C’. He keeps the three samples at different temperatures – A at room temperature, B at 50 °C and C at 95 °C. Which sample will give maximum amount of lather when 10 mL of soap solution is added to each sample and shaken for equal time?
(a) (A) only
(b) Both (A) & (B)
(c) Both (B) and (C)
(d) (C) only
Answer:
(d) C only.

Related Theory
Soap form lather with soft water and at 95° C the hardness of water gets reduced and soap lather in good amount.

Question 32.
Which one of the following compounds can show addition reaction?
(a) C₃H₈
(b) C₄H₈
(c) CH₃Cl
(d) C₂H₅OH

Question 33.
An organic compound of molecular formula C₂H₄O₂ gives brisk effervescence with sodium hydrogen carbonate. The name and formula of the organic compound are:
Select the correct option:

Answer:
(b) The organic compound is ethanoic acid and its formula is CH₃COOH.

Explanation: Ethanoic acid reacts with sodium carbonate and sodium hydrogen carbonate to form sodium ethanoate, carbon dioxide gas, and water.

CH₃COOH + NaHCO₃ → CH₃COONa + CO₂ + H₂O

Question 34.
Carbon compounds have:
(a) High boiling point but low melting point.
(b) High melting but low boiling point.
(c) Low melting and boiling point
(d) High melting and boiling point.
Answer:

Question 35.
The substance used for oxidation of ethanol and the compound formed on oxidation of ethanol is:
Select the correct option:

Answer:

Question 36.
The structure of a hydrocarbon is given below:

Study the structure above and select the correct statements:
(I) The molecular formula of the compound is C₅H₁₂
(II) The IUPAC name of the compound is 2-Methyl pentane
(III) It is an isomer of pentane
(IV) It has 14 single covalent bonds
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) (I), (II), and (III)
(d) (I), (III), and (IV)
Answer:
(b) Both (I) and (III)

Explanation: The structure is that of pentane, whose molecular formula is C₅H₁₂ and it shows isomerism. Structural isomers are compounds with identical molecular formula but different structures.

It has 16 single covalent bonds, – 4 single bonds between carbon atoms and 12 single bonds between C-H atoms.

Question 37.
Which of the following compounds do not contain the Carboxylic acid functional group?
(I) C₂H₅COOH
(II) C₃H₇OH
(III) CH₃COOH
(IV) CH₃CHO
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (III)
(d) Both (II) and (IV)
Answer:
(d) Both (II) and (IV)

Explanation: The functional group carboxylic acid is represented by HCOOH or RCOOH, where R is the alkyl group.

Whereas, the functional group alcohol is represented by ROH and aldehyde by RCHO.
So, (II) is an alcohol, propanol and (IV) is an aLdehyde, ethanal.

Question 38.
The structural formula of propene is:

Answer:

Assertion Reasoning questions Class 10 Science Chapter 2

For the following questions, two statements are given one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is correct explanation of the assertion
(b) Both (A) and (R) are true but (R) is not the correct explanation of the assertion
(c) (A) is true but (R) is false
(d) (A) is false but (R) is true

Question 39.
Assertion (A): Chemical bonds in organic compounds are covalent in nature.
Reason (R): Covalent bond is formed by the sharing of electrons in the bonding atoms. [Diksha]
Answer:
(a) (A) and (R) are true and (R) is the correct explanation of the (A).

Question 40.
Assertion(A): Carbon has a strong tendency to either lose or gain electrons to attain noble gas configuration.
Reason (R): Carbon has four electrons in its outermost shell and has the tendency to share electrons with carbon or other elements.

Question 41.
Assertion (A): Carbon forms covalent compounds with other atoms.
Reason (R): Carbon can gain 4 electrons forming C₄ anion.

Question 42.
Assertion (A): Covalent compounds have low melting and boiling points.
Reason (R): Covalently bonded molecules have weak intermolecular forces.
Answer:
(a) (A) and (R) are true and (R) is the correct explanation of the (A).

Question 43.
Assertion (A): The following belong to the same homologous series: C₂H₄, C₃H₆, C₄H₈.
Reason (R): Gradation in physical properties is seen with an increase in molecular mass in any homologous series.

Question 44.
Assertion (A): Esterification is a process in which a sweet-smelling substance is produced.
Reason (R), When esters react with sodium hydroxide an alcohol and sodium salt of carboxylic acid are obtained.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of the Assertion.

Explanation: Esterification is a process in which esters are formed by the reaction of an acid and alcohol.

Saponification is a process in which an ester is converted back to alcohol and sodium salt of carboxylic acid and it is used in the preparation of soap.

Question 45.
Assertion (A): Following are the members of a homologous series: CH₃OH, CH₃CH₃OH, CH₃CH₂CH₂OH
Reason (R): A series of compounds with the same functional group but differing by -CH₂– unit is called a homologous series.

MCQ Questions for Class 10 Science with Answers

Periodic Classification of Elements Class 10 MCQs Questions with Answers

Question 1.
Which of the following statements) about the modern periodic table are incorrect?
(I) The elements in the modern periodic table are arranged on the basis of their decreasing atomic numbers.
(II) The elements in the modern periodic table are arranged on the basis of their increasing atomic masses.
(III) Isotopes are placed in adjoining group(s) in the periodic table.
(IV) The elements in the modern periodic table are arranged on the basis of their increasing atomic number.
(a) Only (I)
(b) (I), (II), and (III)
(c) (I), (II), and (IV)
(d) Only (IV)
Answer:
(b) (I), (II), and (III)

Explanation: The modern periodic table is a tabular arrangement of elements in increasing order of their atomic number, which is why isotopes are placed at the same position. Hence, only (III) is correct.

Question 2.
Which of the following statements about the modern periodic table is correct?
(a) It has 18 horizontal rows known as periods.
(b) It has 7 vertical columns rows known as periods.
(c) It has 18 vertical columns known as groups.
(d) It has 7 horizontal rows known as groups.
Answer:

Question 3.
An element X is forming the acidic oxide. Its most probable position in the modern periodic table is:
(a) Group 1 and Period 3
(b) Group 16 and Period 3
(c) Group 17 and Period 3
(d) Group 2 and Period 3
Answer:

Question 4.
Which of the given elements A, B, C, D and E with atomic numbers 2, 3, 7,10 and 30 respectively belong to the same period?
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E
Answer:

Question 5.
On the basis of the electronic configuration of x|, the group number and period of the element ‘X is:
(a) Group 15 period 2
(b) Group 13 period 2
(c) Group 9 period 5
(d) Group 13 period 5
Answer:
(b) Group 13 period 2

Explanation: From X⁹₅, we can have the information as:
X — element
5 — Atomic number
9 — Mass number
The electronic configuration of X is 2, 3.

Group number is found out on the basis of valance electrons. Valence electrons are 3 so group number is 10 + 3 = 13.

Period can be found out by knowing the number of shells. Since a number of shells is 2 so it belongs to period 2.

Question 6.
The elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively.
Which pair of elements belongs to the same group?
(a) A and B
(b) B and D
(c) A and C
(d) D and E
Answer:

Question 7.
An element ‘X‘ with atomic number 11 forms a compound with element ‘V with atomic number 8. The formula of the compound formed is:
(a) XY
(b) X₂Y
(c) XY₂
(d) X₂Y₃
Answer:
(b) X₂Y

Element X can lose one electron and has a configuration like that of Neon.
X → X⁺ + e^–
Element Y can gain two electrons to acquire noble gas configuration like that of Neon:
Y + 2e^– → Y₂^–
Or we can write

Question 8.
The positions of four elements A, B, C, and D in the modern periodic table are shown below.

Which element is most likely to form an acidic oxide?
(a) A
(b) B
(c) C
(d) D
Answer:

Question 9.
In Mendeleev’s periodic table, gaps were left for the elements to be discovered later. Which of the following element found a place in the periodic table later?
(a) Germanium
(b) Chlorine
(c) Oxygen
(d) Silicon
Answer:

Question 10.
Elements P, Q, R, and S have atomic numbers 11,15,17 and 18 respectively. Which of them are reactive non-metals?
(a) P and Q
(b) P and R
(c) Q and R
(d) R and S
Answer:
(c) Q and R

Question 11.
An element which is an essential constituent of all organic compounds belongs to:
(a) Group 1
(b) Group 14
(c) Group 15
(d) Group 16
Answer:

Question 12.
According to Mendeleev’s periodic law, the elements were arranged in the periodic table in the order of:
(a) Increasing atomic number
(b) Decreasing atomic number
(c) Increasing atomic masses
(d) Decreasing atomic masses
Answer:
(c) Increasing atomic masses

Explanation: Mendeleev’s periodic law is an arrangement of elements in increasing order of their atomic masses as Mendeleev’s periodic law states that, the physical and chemical properties of elements are a periodic function of their atomic masses.

Question 13.
Which of the following is the outermost shell for elements of period 2?
(a) K shell
(b) L shell
(c) M shell
(d) N shell
Answer:

Question 14.
Which of the following gives the correct increasing order of the atomic radii of O, F, and N?
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N
Answer:

Question 15.
Arrange the following elements in the order of their decreasing metallic character Na, Si, Cl, Mg, Al:
(a) Cl > Si > Al > Mg > Na
(b) Na > Mg > Al > Si > Cl
(c) Na > Al > Mg > Cl > Si
(d) Al > Na > Si > Ca > Mg
Answer:

Question 16.
Which among the following elements has the largest atomic radii?
(a) Na
(b) Mg
(c) K
(d) Ca
Answer:
(c) K

Explanation: Na and Mg belong to the same period, whereas Na and K are in the same group. In a group from top to bottom, the atomic radius increases, whereas it decreases in a period from left to right. Hence, the order would be K > Na > Mg and K > Ca > Mg.

Related Theory
Atomic radius represents the distance from the nucleus to the outer shell of an element.
Trend of the atomic radius in the periodic table:
(1) decreases going from left to right of a period
(2) increases going down a group.

Question 17.
The electronic configurations of three elements X, Y and Z are:
X : 2 Y: 2, 8, 7 Z : 2, 8, 2
Which of the following is correct regarding these elements?
(a) X is a metal
(b) Y is a metal
(c) Z is a non-metal
(d) Y is a non-metal and Z is a metal
Answer:
(d) Y is a non-metal and Z is a metal.

Explanation: Element Y has 1 less electron to complete its octet which is a property of non-metals. On the other hand, element Z has 2 extra electrons to become stable which is a property of metals..

Question 18.
Which of the following elements would lose an electron easily?
(a) Mg
(b) Na
(c) K
(d) Ca
Answer:

Question 19.
Which of the following elements does not lose an electron easily?
(a) Na
(b) F
(c) Mg
(d) Al
Answer:
(b) F

Explanation: Flourine has 7 electrons in the outermost orbit. Its atom size is the smallest too. Since it is the most electronegative element, it does not lose an electron easily. Sodium has one valence electron, magnesium has 2 valence electrons, and aluminium has 3 valence electrons. All these metals lose electrons easily.

Related Theory
Metals can easily lose electrons and exhibit electropositive nature, whereas non-metals have a tendency to accept electrons and exhibit electronegative nature. Na, Al, and Mg are metals, whereas F is non-metal.

Question 20.
What type of oxide would Eka-aluminium form?
(a) EO₃
(b) E₃O₂
(c) E₂O₃
(d) EO
Answer:

Question 21.
The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?
(a) Metal
(b) Metalloid
(c) Non-metal
(d) Left-hand side element
Answer:
(b) Metalloid

Explanation: Atomic number 14 (electronic configuration of 2,8,4) is for silicon element, which is a metalloid and exhibits properties of both metal and non-metal. It has 4 electrons in its valence shell, so it tends to form covalent acidic oxide.

Question 22.
Which one of the following depicts the correct representation of atomic radius (r) of an atom?

(a) (I) and (II)
(b) (II) and (III)
(c) (III) and (IV)
(d) (I) and (IV)
Answer:
(b) (II) and (III)

Explanation: The distance between the center of the nucleus and the outermost shell is known as atomic radius.

Question 23.
Which one of the following does not increase while moving down the group of the periodic table?
(a) Atomic radius
(b) Metallic character
(c) Valence
(d) Number of shells in an element
Answer:

Question 24.
On moving from left to right in a period in the periodic table, the size of the atom:
(a) increases
(b) decreases
(c) does not change appreciably
(d) first decreases and then increases
Answer:
(b) decreases

Explanation: As we move from left to right in the period of periodic table, the number of shell remains same but atomic number increases. So, the increase in nuclear charge which tends to pull electrons closer to the nuclers and reduces the size of the atoms.

Related Theory
The size of atom of an inert gas is bigger than that of the preceding halogen atom. The greater size of the inert gas atom in a period is due to the structural stability of its outermost shell consisting of an octet of electrons.

Question 25.
Which of the following set of elements is written in order of their increasing metallic character?
(a) Be, Mg, Ca
(b) Na, Li, K
(c) Mg, Al, Si
(d) C, O, N
Answer:
(a) Be, Mg, Ca.

Explanation: As we move down in a group, the metallic nature of elements increases. Be, Mg, and Ca are present in the same group (group 2 of the modern periodic table). Thus, Ca has the highest metallic character.

Question 26.
An element X makes an oxide with the formula X₂O₃. This element will be in the same group as:
(a) Na
(b) Mg
(c) Al
(d) Cl [Diksha]
Answer:
(c) Al

Explanation: The answer is Al (aluminium). The element Al is in group II! of Mendeleev’s periodic table, in which the general formula of the oxides of elements is X₂O₃.

Question 27.
The two pairs of elements placed by Newlands in one slot are:
(a) Co, Ni and Ce, La
(b) Be, Mg and Co, Ni
(c) F, Cl, and Ce, La
(d) Zn, Sr, and Be, Mg
Answer:

Question 28.
The order of metallic character of some elements is: N < P < As < Sb < Bi. Identify the most electronegative among these elements,
(a) N
(b) P
(c) Sb
(d) Bi
Answer:
(a) N

Explanation: The less metallic an element, the more electro-negative it will be. Since electronegativity is the ability of an atom to gain electrons, whereas metallic character is related to the ability of atoms to lose electrons. As N is the least metallic of the given elements, it will be the most electronegative.

Question 29.
Four elements P, Q, R and S have number of valence electrons 2,3,5 and 7 respectively. A student noted down the Group number in Modern Periodic Table and their valency as:

Select the row containing the correct group number and valency.
Answer:

Question 30.
Consider the elements Li, Be, B, C, N, O and F.
(I) The most electropositive element is F.
(II) The most electronegative element is F.
(III) The only metalloid is B.
(IV) The smallest atomic size is Li.
Read the statements given above and select the incorrect statements:
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)
Answer:
(b) Both (I) and (IV)

Explanation: Let us arrange the given elements according to their atomic number:
Li < Be < B < C < N < 0 < F.

All the above elements have two occupied shells and are therefore placed in the second group of the periodic table.

The most electropositive element is Li and the most electronegative element is F. This is because the tendency to lose electrons decreases as we go from left to right along a period. Also, as we go from left to right along a period, the atomic radius and hence the atomic size decreases because of the increase in effective nuclear charge experienced by the valence electrons. The only metalloid is B.

Question 31.
Out of the elements F, Cl, Br and I, which is the most electronegative element?
(a) F
(b) Cl
(c) Br
(d) I
Answer:
(a) F

Explanation: The electronegativity decreases as we move down a group because the ability to gain electrons decreases down a group. This is because of the decrease in the effective nuclear charge experienced by the valence electrons since a new shell is added in each group.

Since F, Cl, Br and I have 2, 3, 4 and 5 shells respectively, F is the most electronegative of these elements.

Assertion Reasoning questions Class 10 Science Chapter 5

For the following questions, two statements are given-one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 32.
Assertion (A): Potassium has a bigger atomic radius than lithium.
Reason (R): Atomic radius decreases along a period. [Diksha]

Question 33.
Assertion (A): Chemical properties of the elements belonging to the same group are the same.
Reason (R): Elements belonging to the same group possess the same number of valence electrons.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of A.

Question 34.
Assertion (A): Nitrogen is a non-metal.
Reason (R): Nitrogen has 5 valence electrons.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A)

Explanation: Non-metals are the elements that form negative ions by gaining electrons.

Electronic configuration of N = 2 5
k = 2
L = 5
It needs 3 electrons to complete its octet and achieve the same configuration as that of the inert gas neon.
N + 3e^– → N^3-

Question 35.
Assertion (A): Newland’s law of Octaves worked well with lighter elements only.
Reason (R): Newland assumed that only 56 elements existed in nature.

Question 36.
Assertion (A): A correct position could not be assigned to hydrogen in Mendeleev’s periodic table.
Reason (R): Mendeleev Periodic Law states that ‘the properties of elements are the periodic function of their atomic numbers.
Answer:
(c) (A) is true but (R) is false

Explanation: A correct position could not be assigned to hydrogen in the periodic table. The electronic configuration of hydrogen resembles that of alkali metals. Like alkali metals, hydrogen combines with halogens, oxygen and sulfur to form compounds having similar formulae.

On the other hand, just like halogens, hydrogen also exists as diatomic molecules and it combines with metals and non-metals to form covalent compounds.

Moreover, Mendeleev’s Periodic Law states that ‘the properties of elements are the periodic function of their atomic masses’.

Question 37.
Assertion (A): The elements Sodium (Na), Magnesium (Mg), Aluminium (Al) belong to the same group in Modern Periodic Table.
Reason (R): Atoms of different elements with the same number of occupied shells are placed in the same period.

Question 38.
Assertion (A): Calcium (Atomic No. 20) is more metallic than Potassium (Atomic No. 19).
Reason (R): The tendency to lose electrons decreases as we move from left to right in a period.
Answer:
(c) (A) is false but (R) is true.

Explanation: Potassium (Atomic No. 19) is more metallic than Calcium (Atomic No. 20) as the tendency to lose electrons decreases as we move from left to right in a period.

The electronic configuration of Potassium is 2, 8, 8, 1 and that of Calcium is 2, 8, 8, 2. Therefore, the effective nuclear charge acting on the valence electrons of Calcium will be more than that of Potassium.

MCQ Questions for Class 10 Science with Answers

Life Processes Class 10 MCQs Questions with Answers

Question 1.
If salivary amylase is lacking in the saliva, which of the following events in the mouth cavity wilL be affected?
(a) Proteins breaking down into amino acids
(b) Starch breaking down into sugars
(c) Fats breaking down into fatty acids and glycerol
(d) Absorption of vitamins
Answer:
(b) Starch breaking down into sugars

Explanation: The process of digestion begins in the mouth. The mouth contains a digestive enzyme, salivary amylase. This enzyme breaks the starch molecules in the food, into maltose. The absence of amylase in the saliva thus affects the breakdown of starch into simpler sugar molecules.

Question 2.
In the excretory system of human beings, some substances in the initial filtrate such as glucose, amino acids, salts and water are selectively reabsorbed in:
(a) Urethra
(b) Nephron
(c) Ureter
(d) Urinary bladder
Answer:
(b) Nephron.

Explanation: A nephron is a filtering unit present in kidney. It has different parts like Bowman’s capsule, glomerulus and tubuLar region (Renal tubule). Glucose, amino acids and salts are selectively reabsorbed in tubular region.

Question 3.
Which part of alimentary canal receives bile from the liver?
(a) Stomach
(b) Small intestine
(c) Large intestine
(d) Oesophagus
Answer:
(b) Small intestine

Explanation: Bile is secreted by the liver and is stored in the gall bladder from where it enters the small intestine via a common duct.

Related Theory
It performs two functions:

1. makes the food alkaline.
2. breaks the fats present in food into small globules by the process of emulsification.

Question 4.
Pseudopodia are:
(a) small hair-like structures present on unicellular organisms.
(b) false feet developed in some unicellular organisms.
(c) long, tube-like structures coming out of the mouth.
(d) suckers which are attached to the walls of the intestines.
Answer:

Question 5.
A few drops of iodine solution were added to rice water. The solution turned blue-black in colour. This indicates that the rice water contains:
(a) Complex proteins
(b) Simple proteins
(c) Fats
(d) Starch
Answer:
(d) Starch

Explanation: Iodine solution is often used for testing the presence of starch in the food particles. When iodine is added to starch, it turns blue-black. Rice water contains starch, hence when iodine solution is added to rice water it turns blue-black.

Question 6.
which one of the following statements is correct about the human circulatory system?
(a) Blood transports only oxygen and not carbon dioxide.
(b) Human heart has five chambers.
(c) Valves ensure that the blood does not flow backwards.
(d) Both oxygen-rich and oxygen-deficient blood gets mixed in the heart.
Answer:

Question 7.
Anaerobic process:
(a) takes place in yeast during fermentation.
(b) takes place in the presence of oxygen.
(c) produces only energy in the muscles of human beings.
(d) produces ethanol, oxygen and energy.
Answer:
(a) takes place in yeast during fermentation.

Explanation: (a) Anaerobic respiration (in absence of oxygen) in yeast is known as fermentation as ethanol (alcohol) carbon dioxide and 2 ATP molecules of energy is produced from glucose.

carbon dioxide + 2 ATP molecules of energy
(b) Aerobic respiration takes place in presence of oxygen and anaerobic in absence of oxygen.
(c) In muscles of human beings: Lack of oxygen or absence of oxygen results into the formation of lactic acid and very less amount of energy.
(d) Ethanol and carbon dioxide are produced. Energy is neither produced nor released.

Question 8.
When air is blown from mouth into a test tube containing Lime water, the lime water turns milky due to the presence of
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Water vapour
Answer:

Question 9.
Most of the digestion and absorption of the food takes place in the:
(a) small intestine
(b) liver
(c) stomach
(d) large intestine
Answer:
(a) small intestine.

Explanation: Small intestine receives juices from liver, pancreas and walls of small intestine. Bite juice from liver emulsifies the fats and makes the medium alkaline. Pancreas and small intestine juices contain amylase, lipase and tryspin.

The function of these enzymes ore:

Question 10.
Which of the foL[owing statement (s) is (are) true about respiration?
(I) During inhalation ribs move inward and the diaphragm is raised.
(II) In the alveoli, the exchange of gases takes place i.e. oxygen from alveolar air diffuses into bLood and carbon dioxide from the blood into the alveolar air.
(III) Haemoglobin has a greater affinity for carbon dioxide than oxygen.
(IV)Atveoti increases surface area for the exchange of gases.
(a) (I) and (IV)
(b) (II) and (III)
(c) (I) and (III)
(d) (II) and (IV)
Answer:

Question 11.
Which is the correct sequence of air passage during inhalation?
(a) Nostrils → Larynx → Pharynx → Trachea → Lungs
(b) Nasal passage → Trachea → Pharynx → Larynx → Alveoli
(c) Larynx → Nostrils → Pharynx → Lungs
(d) Nostrils → Pharynx → Larynx → Trachea → Alveoli
Answer:
(d) Nostrils → Pharynx → Larynx → Trachea → Alveoli

Question 8.
When air is blown from mouth into a test tube containing lime water, the lime water turns milky due to the presence of:
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Water vapour
Answer:

Question 9.
Most of the digestion and absorption of the food takes place in the:
(a) small intestine
(b) liver
(c) stomach
(d) large intestine
Answer:
(a) small intestine.

Explanation: Small intestine receives juices from liver, pancreas and walls of small intestine. Bile juice from liver emulsifies the fats and makes the medium alkaline. Pancreas and small intestine juices contain amylase, lipase and tryspin.

The function of these enzymes are:

Question 10.
Which of the following statement (s) is (are) true about respiration?
(I) During inhalation, ribs move inward and diaphragm is raised.
(II) In the alveoli, exchange of gases takes place i.e. oxygen form alveolar air diffuses into blood and carbon dioxide from blood into alveolar air.
(III) Haemoglobin has greater affiinity for carbon dioxide than oxygen.
(IV) Alveoli increases surface area for exchange of gases.
Answer:

Question 12.
During respiration, the exchange of gases take place in:
(a) Trachea and Larynx
(b) Alveoli of lungs
(c) Alveoli and throat
(d) Throat and larynx
Answer:

Question 13.
Single circulation, i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by:
(a) Labeo, Chameleon, Salamander
(b) Hippocampus, Exocoetus, Anabas
(c) Hyla, Rana, Draco
(d) whale, dolphin, turtle
Answer:
(b) Hippocampus, Exocoetus, Anabas

Explanation: Fishes have two-chambered heart and exhibit single circulation, while three-chambered heart of amphibians and reptiles and four-chambered heart of birds and mammals exhibit double circulation.

Question 14.
In which of the following vertebrate group/ groups, does heart not pump oxygenated blood to different parts of the body?
(a) Pisces and amphibians
(b) Amphibians and reptiles
(c) Amphibians only
(d) Pisces only
Answer:
(d) Pisces only

Explanation: Fishes have only two-chambered heart and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body. Fishes take in water through their mouths and force it past the gills where the dissolved oxygen is taken up by blood.

Question 15.
Which of the following statements about the autotrophs is incorrect:
(a) They synthesize carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll
(b) They store carbohydrates in the form of starch
(c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight
(d) They constitute the first trophic level in food chains
Answer:
(c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight Explanation: Autotrophs obtain the required carbon and energy requirements from carbon dioxide and Sunlight. They combine carbon dioxide and water to form carbohydrates.

Question 16.
Oxygen liberated during photosynthesis comes from:
(a) Water
(b) Chlorophyll
(c) Carbon dioxide
(d) Glucose
Answer:

Question 17.
The blood leaving the tissues becomes richer in:
(a) Carbon dioxide
(b) Water
(c) Haemoglobin
(d) Oxygen
Answer:
(a) Carbon dioxide

Explanation: The blood leaving the tissues becomes richer in carbon dioxide. When the oxygenated blood passes through the capillaries of the tissue, it gives oxygen to the body cells and takes carbon dioxide, produced during cellular respiration. Thus, it becomes richer in carbon dioxide.

Question 18.
The xylem in plants are responsible for:
(a) Transport of water
(b) Transport of food
(c) Transport of amino acids
(d) Transport of oxygen
Answer:
(a) Transport of water
Explanation: Xylem tissues include tracheids, vessels, fibres and parenchyma and serve in the ascent of sap/water and minerals.

Related Theory
Phloem tissues comprised of four elements: sieve, companion cell, phloem fibres and phloem parenchyma. They serve in the translocation of organic nutrients.

Question 19.
Which of the following is an incorrect statement?
(a) Organisms grow with time.
(b) Organisms must repair and maintain their structure.
(c) Movement of molecules does not take place among cells.
(d) Energy is essential for life processes.
Answer:

Question 20.
The internal (cellular) energy reserve in autotrophs is:
(a) Glycogen
(b) Protein
(c) Starch
(d) Fatty acid
Answer:
(c) Starch

Explanation: The food prepared in the plant (autotrophs) by the process of photosynthesis is glucose that gets stored in various plant parts in the form of starch.

Question 21.
Choose the event that does not occur in photosynthesis.
(a) Absorption of light energy by chlorophyll
(b) Reduction of carbon dioxide to carbohydrates
(c) Oxidation of carbon to carbon dioxide
(d) Conversion of light energy to chemical energy
Answer:

Question 22.
Choose the forms in which most plants absorb nitrogen:
(I) Proteins
(II) Nitrates and Nitrites
(III) Urea
(IV) Atmospheric nitrogen
(a) (I) and (II)
(b) (II) and (III)
(c) (III) and (IV)
(d) (I) and (IV)
Answer:

Question 23.
The doctor measured Ravi’s blood pressure and said it is normal now. The range of Ravi’s blood pressure (systolic/diastolic) is likely to be:
(a) \(\frac{120}{80}\) mm of Hg
(b) \(\frac{160}{80}\) mm of Hg
(c) \(\frac{120}{60}\) mm of Hg
(d) \(\frac{180}{80}\) mm of Hg
Answer:
(a) \(\frac{120}{80}\) mm of Hg

Explanation: Blood pressure is denoted by two values: one value is above and the other value
is below. The value that is above is the systolic pressure and the one that is below is the diastolic pressure. A normal individual should maintain a systolic/diastolic pressure of \(\frac{120}{80}\) mm of Hg.

Related Theory
Blood pressure is the force applied by the blood against the walls of the arteries. The blood pressure is of two types – systolic and diastolic. The blood pressure of a normal individual is 120/80 mm ofHg. If a person has less blood pressure than normal, he/ she is said to have low blood pressure.

If a person has more blood pressure than normal, he/ she is said to have high blood pressure.

Question 24.
If the structure marked X in the diagram given below is blocked, then which of the processes will not occur?

(a) Transpiration and respiration
(b) Transpiration, photosynthesis and respiration
(c) Respiration, transpiration and transportation
(d) Respiration and photosynthesis [Diksha]
Answer:
(b) Transpiration, photosynthesis and respiration Explanation: Here, the structure marked as X is stomata.
Stomata are responsible for gaseous exchange in the plant. If they are blocked, the gaseous exchange will not take place.

Hence, the two important processes of the plant: photosynthesis and respiration do not take place. Stomata are also responsible for removing extra water present in the plants.

Hence, if blocked, the process of transpiration will also be affected.

Question 25.
Which of the following statement(s) is incorrect about transport in plants:
(I) The transport in the xylem is achieved by utilizing energy.
(II) Transpiration helps in the absorption of water and minerals from the roots to the leaves.
(III) The transport of soluble products of photosynthesis occurs in the phloem.
(IV) Besides water, the xylem also transports amino acids and other substances.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)
Answer:
(c) Both (I) and (IV)

Explanation: Transport of water and minerals in xylem takes place by the process of osmosis due to difference in ionic concentration in the soil and inside the root. Transpiration pull helps in the absorption of water to the taller parts of a plant during the daytime when the stomata are open. The phloem transports the soluble products of photosynthesis, amino acids and some other substances.

Question 26.
Which of the following statements are incorrect about aerobic respiration?
(I) The first step is the breakdown of glucose into pyruvate.
(II) Glucose is a six-carbon molecule and pyruvate is a three-carbon molecule.
(III) The breakdown of glucose take place in the mitochondria.
(IV) The breakdown of pyruvate using oxygen takes place in the cytoplasm.
(a) Both (I) and (III)
(b) Both (II) and (IV)
(c) Both (III) and (IV)
(d) (I), (III) and (IV)
Answer:

Question 27.
A student noted the differences between blood and lymph in the following table. Select the row containing correct information:

Answer:
(d) Blood: It flows through blood capillaries: Lymph: It flows through arteries

Explanation: Lymph drains into Lymph capillaries from the intercellular spaces which join to form large lymph vesseLs that finally open into larger veins.

Question 28.
Select the incorrect statement from the statements given below.
Waste products in plants:
(a) Are stored in the Golgi apparatus.
(b) Are stored in leaves that fall off.
(c) Are stored as resins and gums, especially in old xylem.
(d) Are excreted into the soil around them.
Answer:
(a) Are stored in the Golgi apparatus.

Question 29.
Which of the following part of the human excretory system is under nervous control?
(a) Ureters
(b) Urethra
(c) Urinary bladder
(d) Collecting duct
Answer:
(c) Urinary bladder

Explanation: The urinary bladder is a muscular structure that stores the urine until we get the urge to urinate. It is under nervous control.

Question 30.
In humans, the oxygen-rich blood from the lungs comes to the:
(a) Left atrium.
(b) Right atrium
(c) Left ventricle
(d) Right ventricle
Answer:

Question 31.
Select the incorrect statement:
(a) The arteries have thick, elastic walls
(b) The veins have thin walls
(c) Veins have valves to ensure that blood flows in one direction only.
(d) Arteries have valves to ensure that blood flows in one direction only.
Answer:
(d) Arteries have valves to ensure that blood flows in one direction only.

Explanation: Arteries do not have any valves as they carry blood away from the heart. They have thick and elastic walls as they bLood is under high pressure. Veins have valves to ensure that the blood flows in one direction only.

Assertion Reasoning questions Class 10 Science Chapter 6

For the following questions two statements are given- one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is correct explanation of the assertion.
(b) Both (A) and (R) are true but R is not the correct explanation of the assertion.
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 32.
Assertion (A): Transpiration cools leaf surface.
Reason (R): Transpiration helps in translocation of sugar in plants. [Diksha]
Answer:
(c) (A) is true but (R) is false.

Explanation: Transpiration is the process by which plants lose extra water off their surface with the help of the stomata of the Leaves. The plants usually lose water during very hot season. As a result, the temperature of the plant decreases and it cools down. However, transpiration does not help in translocation of food in the plants. Therefore, the assertion is true but the reason accompanied is false.

Related Theory
Transpiration is an important plant process. The three important tasks that are accomplished due to transpiration are:

1. Decrease in temperature of the plant: When the plants lose water, the temperature of the plant’s decreases and therefore, the plants cool down.
2. Transpirational pull: When plants lose water, an empty space is created in the plants. As a result, the minerals and water from the root are pulled up. This process is called transpirational pull.
3. Plant turgidity: Transpiration helps plants in maintaining the turgidity of the plants.

Question 33.
Assertion (A): The leaves which are partly green and partly white are called variegated leaves.
Reason (R): The green part of such a leaf contains chlorophyll but the writing part does not contain chlorophyll.

Question 34.
Assertion (A): Human beings have a complex respiratory system.
Reason (R): Human skin is impermeable to gases.
Answer:
(b) Both (A) and (R) are correct but the R is not the correct explanation of the Assertion. Explanation: Human skin is impermeable to gas to minimise the loss of water from the skin.

Question 35.
Assertion (A): Autotrophs can produce food on its own.
Reason (R): Green plants can absorb the energy of sunlight that falls on the leaves.
Answer:
(b) (A) is true but (R) is false.

Explanation: All the green plants are called autotrophs. This is due to the fact that the green plants make their own food from very simple substances like carbon dioxide and water that is present in the surroundings.

The green plants in a terrestrial ecosystem capture about 1% energy of sunlight that falls on their leaves and convert it to into food energy.

Question 36.
Assertion (A): Hydrochloric acid secreted in the stomach makes an acidic medium for the action of the enzyme pepsin.
Reason (R): Bile juice from liver will make the medium alkaline in the small intestine for the panereatic juices to act.

Question 37.
Assertion (A): The opening and closing of the pore is a function of the guard cells.
Reason (R): Stomatal pores are the site for an exchange of gases by diffusion.
Answer:
(b) Both (A) and (R) are correct but the R is not the correct explanation of the Assertion.

Related Theory
Tiny pores present on the surface of leaves of plants are called stomata. Each stomatal pore is surrounded by a pair of guard cells.

When water flows into the guard cells, they swell, become curved and cause the pore to open. Similarly when the guard cells lose water, they shrink and the stomatal pore closes.

Question 38.
Assertion (A): Respiration is an exothermic reaction.
Reason (R): Respiration is processes in which glucose combines with oxygen and decompose to carbon dioxide and water this reaction also release some energy.
Answer:
(a) Both A and R are true, and R is correct explanation of the assertion.

Question 39.
Assertion (A): The inner lining of the small intestine does not have numerous finger-like projections called villi.
Reason (R): The villi increase the surface area for absorption.
Answer:
(d) A is false, but R is true.

Explanation: The inner lining of the small intestine have numerous finger-like projections called villi and these villi increase the surface area for absorption. Thus A is false, but R is true.

Question 40.
Assertion (A): Oxygenated blood flows in the pulmonary artery.
Reason (R): Arteries have a narrow lumen.
Answer:

Question 41.
Assertion (A): Glucose is absorbed in the small intestine and reabsorbed by the kidney tubules.
Reason (R): Maximum absorption of glucose takes place in the large intestine.
Answer:
(c) A is true, but R is false.

Explanation: Glucose is absorbed in the small intestine and reabsorbed by the kidney tubules and its maximum absorption takes place in the small intestine. Thus A is true, but R is false

MCQ Questions for Class 10 Science with Answers

Management of Natural Resources Class 10 MCQs Questions with Answers

Question 1.
Which one of the following is responsible for the ……………… water?
(a) Loss of vegetation cover
(b) Diversion for high water demanding crops
(c) Pollution from urban wastes
(d) Afforestation
Answer:

Question 2.
Which of the following are water-intensive crops?
(a) Wheat and rice
(b) Wheat and sugarcane
(c) Sugarcane and rice
(d) Wheat and gram
Answer:
(c) Sugarcane and rice.

Related Theory:
The construction of large dams leads to some problems.
People close to the source grow water-intensive crops like sugarcane and rice whereas people farther downstream do not get sufficient water to grow these crops. This causes social problems resulting due to unequal distribution of water. Other problems related to the construction of dams are economic and environmental problems.

Question 3.
Consider the following criticisms that are generally addressed when a new project is launched:
(I) Displacement of peasants and local tribals without compensation.
(II) Swallowing up large amount of public money without any benefits.
(Ill) Deforestation and loss of biodiversity. The criticisms about large dams in particular are:
(a) (I) and (II)
(b) (II) and (III)
(c) (I) and (III)
(d) (I), (II) and (III)
Answer:

Question 4.
The Reni village of Garhwal is famous for:
(a) Monoculturesofpine,teakand eucalyptus.
(b) Chipko Movement.
(c) Extensive biodiversity.
(d) Participation of local people inefficient management of forests.
Answer:

Question 5.
Which one of the following stakeholders of forests causes the maximum damage to forest?
(a) People who live in or around the forest
(b) The forest department of the government
(c) The wildlife and native enthusiasts
(d) The industrialists
Answer:
(d) The Industrialist

Question 6.
Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic. The factories located near A and B are:
(a) Soaps and detergents factories near A and alcohol distillery near B.
(b) Soaps and detergents factories near B and alcohol distillery near A.
(c) Lead storage battery manufacturing factories near A and soaps and detergents factories near B.
(d) Lead storage battery manufacturing factories near B and soaps and detergents factories near A.
Answer:

Question 7.
A diagram of traditional water harvesting system is given below:
The statement which defines the system and its parts is:

(a) This is an ideal setting of the Khadin system and A = Catchment area; B = Saline area and C = Shallow dug well:
(b) This is an ideal setting of the Shallow dug well system and A = Catchment area; B = Saline area and C = Khadin.
(c) This is an ideal setting of Catchment area and A = Khadin, B = Saline area, and C = Shallow dug well.
(d) This is showing the Saline area and A = Catchment area; B = Khadin and C = Shallow dug well.
Answer:
(a) This is an ideal setting of the Khadin system and:
A = catchment area
B = Saline area
C = Shallow dug well

Explanation: Khadin is a traditional rainwater haversting system in Rajasthan. The main feature of Khadin system of rainwater harvesting is a very long earthen embankment called ‘bund’ built across the lower edge of the sloping farmland. The rainwater from catchment area flows down the slopes and stopped by the bund to form a reservoir the excess water flows through pathwalls (made for this purpose) and filLs the shallow well dug behind the bund. This area is subsequently used for growing crops.

Question 8.
The major ill effect of monoculture practice in forests is on the:
(a) biodiversity which faces large destruction
(b) local people whose basic needs can no longer be met from such forests
(c) industries
(d) forest department
Answer:

Question 9.
Which of the following are not responsible for failure to sustain water availability underground:
(I) Afforestation
(II) Loss of vegetation cover
(III) Diversion for high water demanding crops
(IV) Pollution from industrial effluents and urban wastes.
(a) Only (I)
(b) Only (II)
(c) Both (I) and (III)
(d) Both (II) and (IV)
Answer:

Question 10.
Which among the following factors help in confirming the contamination of river water?
(I) Measurement of pH of river water
(II) Existence of diverse life forms in river water
(III) Presence of chlorine in river water
(IV) Presence of coliform bacteria in river water
Choose the correct option from the following:
(a) (I) and (III)
(b) (II) and (III)
(c) (I) and (IV)
(d) (II) and (IV)

Question 11.
Choose the correct statements among the following that are a consequence of raising the height of dams
(I) Deforestation and the loss of biological diversity.
(II) Displacement of large number of peasantsand tribals without adequate compensation or rehabilitation
(III) Loss of valuable agricultural land.
(IV) Generation of permanent employment for local people
(a) Both (I) and (II)
(b) Both (II) and (IV)
(c) (I), (II) and (III)
(d) (I), (III) and (IV)

Question 12.
Which of these practices can be adopted to save the environment?
(a) Refuse the use of single-use plastic bags
(b) Reduce the use of paper bags
(c) Recycle single-use bags
(d) Reuse waste food
Answer:
(a) Refuse the use of single-use plastic bags Explanation: The 5R’s to save the environment are: Refuse, Reduce, Reuse, repurpose and Recycle. The best way to save the environment is by refusing to use products that may harm the environment.

Question 13.
How does switching off unnecessary electrical appliances help the environment?
(a) It generates electricity when switched off
(b) It reduces wastage of energy
(c) It recycles the amount of energy used
(d) It increases the efficiency of the electrical appliances
Answer:

Question 14.
Which of these is an example of sustainable development in order to conserve natural resources for the future generation?
(a) Cleaning water resources
(b) Finding additional fuel reserves
(c) Clearing forests to set up new industries
(d) Planning for safe disposal of wastes after mining
Answer:

Question 15.
Which of the following industries would be identified as a stakeholder involved in a forest?
(a) That manufacture ceramic products using clay
(b) That make papers using wood products
(c) That make clothes using synthetic materials
(d) That manufacture device that generate electricity using solar energy
Answer:

Question 16.
Which of the following practices will help to conserve the forest?
(a) Deforestation
(b) Banning deforestation
(c) Increased use of firewood by local people
(d) Increased use of timber by industries
Answer:

Question 17.
Which of these explains the use of dams?
(a) To replenish underground water resources
(b) To produce steady supply of water in hilly regions
(c) To provide irrigation and generate electricity
(d) To provide water for conservation of biological diversity
Answer:

Question 18.
Which of the following steps should be adopted in order to save the environment?
(a) Replace coal to firewood for cooking food
(b) Replace petroleum to coal in vehicles for transportation
(c) Replace thermal power with solar power to generate electricity
(d) Replace the use of coal to petroleum for melting metals in a furnace
Answer:

Assertion Reasoning questions Class 10 Science Chapter 16

For the following questions, two statements are given – one labeled Assertion (A) and other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 19.
Assertion (A): Sustainable development implies a change in all aspects of life.
Reason (R): Economic development is linked to environmental conservation.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.

MCQ Questions for Class 10 Science with Answers

Control and Coordination Class 10 MCQs Questions with Answers

Question 1.
The electrical impulse travels in a neuron from:
(a) Dendrite Axon → Axonal end → Cell body
(b) Cell body → Dendrite → Axon → Axonal end
(c) Dendrite → Cell body → Axon → Axonal end
(d) Axonal end → Axon → Cell body Dendrite
Answer:
(c) Dendrite → Cell body → Axon → Axonal end

Explanation: The electrical impulse travels from the dendrite to the cell body, and then along the axon to its axonal end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.

Question 2.
In a synapse, a chemical signal is transmitted from:
(a) The dendritic end of one neuron to the axonal end of another neuron.
(b) Axon to cell body of the same neuron.
(c) Cell body to the axonal end of the same neuron.
(d) The axonal end of one neuron to the dendritic end of another neuron.
Answer:
(d) The axonal end of one neuron to the dendritic end of another neuron.

Explanation: The chemical signal is transmitted from axonal end of one neuron to the dendritic end of another nueron. This microscopic gap is called synapse.

Question 3.
In a neuron, the conversion of electrical signal to a chemical signal occurs at/in:
(a) Cell body
(b) Axonal end
(c) Dendritic end
(d) Axon
Answer:

Question 4.
Which is the correct sequence of the components of a reflex arc?
(a) Receptors Muscles → Sensory neuron → Motor neuron → Spinal cord
(b) Receptors → Motor neuron → Spinal cord Sensory neuron → Muscle
(c) Receptors → Spinal cord → Sensory neuron → Motor neuron → Muscle
(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle
Answer:
(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Explanation: A stimulus received by the receptors present on skin, is transmitted to the sensory neuron, which carries it to the central nervous system (the spinal cord and brain).

A motor neuron carries the message from the central nervous system to the effector which could be a muscle, a gland or both.

Related Theory
Nerve based pathway performed by an impulse from the receptor of stimulus to the effector organ is called the reflex arc. A reflex action is a nerve mediated automatic and spontaneous response to a certain stimulus without sonsulting the wilt of the individual coughing, sneezing, etc.

Question 5.
Which of the following statements are true?
(I) Sudden action in response to something in the environment is called a reflex action.
(II) Sensory neurons carry signals from the spinal cord to muscles.
(III) Motor neurons carry signals from receptors to the spinal cord.
(IV) The path through which signals are transmitted from a receptor to muscle or a gland is called reflex arc.
(a) (I) and (II)
(b) (I) and (III)
(c) (I) and (IV)
(d) (I) (II) and (III)
Answer:
(c) (I) and (IV)

Explanation: Reflex action is a sudden action in response to some stimuli in the environment. Reflex arc is the path through which signals are transmitted from a receptor to a muscle or a gland.

Question 6.
Which of the following statements are true about the brain?
(I) The main thinking part of bi in is the hindbrain.
(II) Centres of hearing, smell, memory, sight, etc. are located in the fore-brain.
(III) Involuntary actions like salivation, vomiting and blood pressure are controlled by the medulla in the hind brain.
(IV) Cerebellum does not control posture and balance of the body.
(a) (I) and (II)
(b) (I) (II) and (III)
(c) (II) and (III)
(d) (III) and (IV)
Answer:

Question 7.
The spinal cord originates from:
(a) Cerebrum
(b) Medulla
(c) Pons
(d) Cerebellum
Answer:

Question 8.
The movement of shoot towards light is:
(a) Geotropism
(b) Hydrotropism
(c) Chemotropism
(d) Phototropism

Question 9.
The main function of abscisic acid in plants is to:
(a) Increase the length of cells
(b) Promote cell division
(c) Inhibit growth
(d) Promote growth of stem
Answer:
(c) Inhibit growth

Explanation: Abscisic acid (ABA) is one example of a hormone which inhibits growth. Its effects include wilting of leaves.

Related Theory
Auxin is synthesized at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light.

Gibberellin helps in the growth of the stem.

Cytokinin promotes cell division, and it is natural then that they are present in greater concentration in areas of rapid cell division, as in fruits and seeds.

Abscisic acid inhibits growth. Its effects include wilting of leaves. It is also responsible for falling of senescent leaves.

Question 10.
Iodine is necessary for the synthesis of which hormone?
(a) Adrenaline
(b) Thyroxin
(c) Auxin
(d) Insulin
Answer:
(b) Thyroxin

Explanation: Iodine is necessary for the thyroid gland to make the thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin. In case iodine is deficient in our diet, there is a possibility that we might suffer from goitre. One of the symptoms in this disease is a swollen neck.

Question 11.
Choose the incorrect statement about insulin:
(a) It is produced from pancreas.
(b) It regulates growth and development of the body.
(c) It regulates blood sugar levels.
(d) Insufficient secretion of insulin will cause diabetes.
Answer:

Question 12.
Select the mismatched pair:
(a) Adrenaline – Pituitary gland
(b) Testosterone – Testes
(c) Oestrogen – Ovary
(d) Thyroxin – Thyroid gland
Answer:
(a) Adrenaline – Pituitary gland

Explanation: Adrenaline is secreted by the adrenal gland, whereas growth hormone is secreted by the pituitary gland.

Question 13.
The growth of tendril in pea plants is due to:
(a) The effect of light.
(b) The effect of gravity.
(c) Rapid cell divisions in tendrillar cells that are away from the support.
(d) Rapid cell divisions in tendrillar cells in contact with the support.
Answer:

Question 14.
The growth of pollen tubes towards ovules is due to:
(a) Hydrotropism
(b) Chemotropism
(c) Geotropism
(d) Phototropism
Answer:

Question 15.
The movement of sunflower in accordance with the path of the sun is due to:
(a) Phototropism
(b) Geotropism
(c) Chemotropism
(d) Hydrotropism
Answer:

Question 16.
Involuntary actions in the body are controlled by:
(a) Medulla in the forebrain
(b) Medulla in the midbrain
(c) Medulla in the hindbrain
(d) Medulla in the spinal cord
Answer:
(c) Medulla in the hindbrain

Explanation: Medulla is a part of the hindbrain and controls involuntary action.

Question 17.
Which of the following is not an involuntary action?
(a) Vomiting
(b) Salivation
(c) Heartbeat
(d) Chewing
Answer:
(d) Chewing

Explanation: The actions that are not under our direct control are known as involuntary actions. Vomiting, salivation and heartbeat are examples of involuntary action. These involuntary actions are controlled by the medulla in the hindbrain.

Question 18.
A doctor advised a person to take an injection of insulin because:
(a) His blood pressure was low.
(b) His heart was beating slowly.
(c) He was suffering from goitre.
(d) His sugar level in blood was high.
Answer:
(d) His sugar level in blood was high.

Explanation: A person taking injections of insulin is suffering from diabetes. Insulin is a hormone which is produced by the pancreas. It helps in regulating blood sugar levels. If not secreted in proper amounts, the sugar level in the blood rises, causing many harmful effects.

Question 19.
The hormone which increases fertility in males is called:
(a) Oestrogen
(b) Testosterone
(c) Insulin
(d) Growth hormone
Answer:
(b) Testosterone

Explanation: Testosterone is the male sex hormone necessary for sperm production. In addition to regulating the formation of sperms, testosterone brings changes in appearance seen in boys, at the time of puberty.

Question 20.
Which of the following endocrine glands is unpaired?
(a) Adrenal
(b) Testes
(c) Pituitary
(d) Ovary
Answer:

Question 21.
The junction between two neurons is called:
(a) Cell junction
(b) Neuromuscular junction
(c) Neural joint
(d) Synapse
Answer:
(d) Synapse

Related Theory

• Synapse is the junction between two neurons.
• Cell junction is junction between neighboring cells.
• Neuromuscular junction allows delivery of impulses from neurons to other cells, like muscles cells/gland.

Question 22.
In humans, life processes are controlled and regulated by:
(a) Reproductive and endocrine systems.
(b) Respiratory and nervous systems.
(c) Endocrine and digestive systems.
(d) Nervous and endocrine systems.
Answer:

Question 23.
Select the row containing incorrect information:

Endocrine Gland	The function of hormone secreted
(a) Thyroid	Regulates carbohydrate, protein and fat metabolism
(b) Pituitary	Regulates growth and development of the body
(c) Pancreas	Increasing blood sugar levels
(d) Adrenal	Increasing heart rate

Answer:
(c) Endocrine Gland: Pancreas; Function of hormone – Increasing blood sugar levels

Question 24.
Look at the figure below and identify the structure labelled incorrectly:


Answer:
(d) D-Dendrite

Explanation: Part labelled D is capillary and not dendrite, as dendrites receive nerve impulses.

Question 25.
Given below are four statements regarding endocrine glands and hoimones. Select the correct statements:
(I) Hormones are secreted by the endocrine glands.
(II) Some endocrine glands secrete hormones in response to other hormones.
(III) Hormones are required in large quantities.
(IV) Many hormones are controlled by some form of a feedback mechanism.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) (I), (II), and (III)
(d) (I), (II), and (IV)
Answer:
(d) (I), (II), and (IV)

Explanation: Hormones are very potent substances, which means that very small amounts of a hormone may have profound effects on metabolic processes. Some endocrine glands secrete hormones in response to other hormones. The hormones that cause the secretion of other hormones are called tropic hormones. A hormone from gland A causes gland B to secrete its hormone. Many hormones are controlled by some form of a negative feedback mechanism, in this type of system, a gland is sensitive to the concentration of a substance that it regulates. A negative feedback system causes a reversal of increases and decreases in body conditions in order to maintain a state of stability.

Question 26.
Given below are four statements regarding the movement in plants.
Select the incorrect statements.
(I) Movement in plants happens at a point as the point of touch.
(II) The plants use electrical-chemical means to convey information from cell to cell.
(III) There are specialised tissues in plants for the conduction of information.
(IV) Plant cells change shape by changing the amount of water in them
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)
Answer:

Question 27.
The junction between two nerves is known as:
(a) Synapse
(b) Axon
(c) Dendrite
(d) Capillary
Answer:
(a) Synapse

Explanation: The junction between two neurons is known as synapse. It is the site of transmission of nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector). A synaptic connection between a neuron and a muscle cell is called a neuromuscular junction.

Question 28.
The plant hormone that promotes dormancy m seeds and buds is:
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Abscisic acid
Answer:
(d) Abscisic acid

Explanation: Abscisic acid is one example of a hormone which inhibits growth. Its effects include wilting of leaves and promoting dormancy in seeds and buds.

Question 29.
The secretion of which hormone leads to physical changes in the body when you are 10-12 years of age?
(a) Oestrogen from testes and testosterone from ovary.
(b) Oestrogen from adrenal gland and testosterone from pituitary gland.
(c) Testosterone from testes and Oestrogen from ovary.
(d) Testosterone from thyroid gland and Oestrogen from pituitary gland.

Assertion Reasoning questions Class 10 Science Chapter 7

For the following questions, two statements are given: one labeled Assertion (A) and the other labeled Reason (R) Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 30.
Assertion (A): A growing plant appears to bend towards the direction of light.
Reason (R): The plant hormone auxin diffuses towards the shady side of the shoot.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).

Question 31.
Assertion (A): Plants convey the acquired information from cell to cell.
Reason (R): Plants have specialized tissues for the conduction of information.
Select the correct answer to the above question from the codes (a), (b), (c) and (d) as given below:

Question 32.
Assertion (A): In animals, the brain is the main controlling center for responding to changes in their environment.
Reason (R): The thinking process of the brain is not fast enough in animals.
Answer: (d) (A) is false, but (R) is true.

Explanation: Reflex arcs have evolved in animals as the thinking process of the brain is not fast enough. Reflex action is any spontaneous, involuntary, and automatic response to a stimulus due to a change in our environment. For e.g. when a person touches a hot plate a sudden action leading to the withdrawal of hand occurs in a certain manner, this path of manner determines the reflex arc.

Reflex arcs have evolved in animals in order to take sudden and involuntary actions which are required in certain circumstances where emergency response is required to save the body from situations that may lead to danger.

MCQ Questions for Class 10 Science with Answers

How do Organisms Reproduce? Class 10 MCQs Questions with Answers

Question 1.
Fertilisation is the process of:
(a) transfer of male gamete to female gamete.
(b) fusion of nuclei of male and female gamete.
(c) adhesion of male and female reproductive organs.
(d) the formation of gametes by a reproductive organ.
Answer:
(b) Fusion of nuclei of male and female gamete.

Explanation: Fertilization is the fusion of nucleus of male and female garnets to form a single cell called as zygote. Fertilization occurs in sexually reproducing organisms.

Related Theory:
During sexual mode of reproduction germ cells (gametes) of two individuals need to fuse together. It can happen by either of the following:

External release of germ cells from body of an individual as seen in angiospermic plants, frog, fish etc. This is known as external fertilization.

Internal transfer of germ cells by physical contact between male and female organisms as in mammals. This is called internal fertilization.

Question 2.
Characters that are transmitted from parents to offsprings during reproduction show:
(a) OnLy similarities with parents
(b) Only variations with parents
(c) Both similarities and variations with parents
(d) Neither similarities nor variations
Answer:

Question 3.
Choose the correct statement(s) on budding in yeast from the foLlowing:
(I) A parent celL divides into two or more daughter ceLLs and here the parent identity is Lost.
(II) In this the eLongated nucLeus divides to form two or more daughter nucLei.
(III)A bud arises from a particuLar region on a parent body.
(IV)After detaching from the parent body the bud grows into a new independent individual.
(a) (I) only
(b) (III) only
(c) (II) and (III) only
(d) (III) and (IV) only
Answer:
(d) (III) and (IV) only

Explanation: Yeast reproduces asexually by the process of budding in which a bud arises from a particular region on a parent body. And after detaching from the parent body the bud grows into a new independent individual.
Statements I and II are for binary and multiple fission respectively.

Question 4.
The number of chromosomes in parents and offsprings of a particular species remains constant due to:
(a) Doubling of chromosomes after zygote formation
(b) Halving of chromosomes during gamete formation
(c) Doubling of chromosomes after gamete formation
(d) Halving of chromosomes after gamete formation
Answer:

Question 5.
In the following figure, different stages of binary fission in amoeba are depicted, which are not in the proper sequence
Answer:

The correct sequence is
(a) (II), (III), (IV), (I) (b) (I), (II), (IV), (III)
(c) (III), (IV), (II), (I) (d) (I), (III), (IV), (II)
[CBSE 2017]
Ans. (a) (II), (III), (IV), (I)
Explanation: The correct sequence of the different stages of binary fission in amoeba is:
(II) Parent amoeba cell.
(III) Duplication of the genetic material and elongation of the nucleus.
(IV) Nuclear division and constriction in cytoplasm
(I) Formation of two daughter amoeba cells.

Question 6.
In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called:
(a) Filaments
(b) Hyphae
(c) Rhizoids
(d) Roots
Answer:

Question 7.
Select the correct statements for the process of budding in yeast:
(I) A bud arises from a particular region on a parent body.
(II) A parent cell divides into two daughter cells, here the parent identity is lost.
(III) Before detaching from the parent body a bud may form another bud.
(IV) A bud when detaches from the parent body grows into a new individual.
(a) (I), (II) and (III)
(b) (II), (III) and (IV)
(c) (III), (IV) and (I)
(d) (IV), (I) and (II)
Answer:

Question 8.
Slides of binary fission in Amoeba and budding in yeast were given for observation to a group of students. Some of the observations reported by the group are given below:
(I) Cytokinesis was observed in the yeast cell.
(II) A chain of buds were observed in Amoeba.
(III) Single cell of Amoeba and single cell of yeast were undergoing binary fission and budding respectively.
(IV) Elongated nucleus was dividing to form two daughter nuclei in Amoeba.
The correctly reported observations are:
(a) (I) and (II)
(b) (II) and (III)
(c) (III) and (IV)
(d) (I) and (IV)
Answer:
(c) (III) and (IV)

Question 9.
Which of the following statements are true for flowers?
(I) Flowers are always bisexual
(II) They are the sexual reproductive organs
(III) They are produced in all groups of plants
(IV) After fertilization they give rise to fruits
(a) (I) and (IV)
(b) (II) and (III)
(c) (I) and (III)
(d) (II) and (IV)
Answer:
(d) (II) and (IV) i.e. they are the sexual reproductive organs and after fertilization they give rise to fruits

Explanation: Flowers are the sexually reproductive organs of a plant and a fertilized flower give rise to fruit.

Question 10.
During adolescence, several changes occur in the human body. Mark one change from the following associated with sexual maturation in boys:
(a) loss of milk teeth
(b) increase in height
(c) cracking of voice
(d) weight gain
Answer:

Question 11.
Which among the following statements are true for sexual reproduction in flowering plants?
(I) It requires two types of gametes.
(II) Fertilisation is a compulsory event.
(III) It always results in the formation of zygote.
(IV) Offsprings formed are clones.
(a) (I) and (IV)
(b) (I), (II) and (IV)
(c) (I), (II) and (III)
(d) (I), (II) and (III)
Answer:

Question 12.
Characters transmitted from parents to offspring are present in:
(a) Cytoplasm
(b) Ribosome
(c) Golgi bodies
(d) Genes
Answer:
(d) Genes

Explanation: Genes are the unit of heredity DNA that determine genetic characters in an organism.

Question 13.
Semen which contains millions of sperms also contains secretions of seminal vesicle and prostrate gland (accessory glands). It makes the tranport of sperms easier and provide nutrition to sperms.
Correct sequence of organs in the male reproductive system for transport of sperms is:
(a) Testis → vas deferens → urethra
(b) Testis → ureter → urethra
(c) Testis → urethra → ureter
(d) Testis → vas deferens → ureter
Answer:
(a) Testis → vas deferens → urethra

Explanation: Testis produces sperms or germ cells. The sperms formed are delivered through the vas deferens which unites with a tube coming from the urinary bladder. The urethra thus forms a common passage for both the sperms and urine.

Question 14.
Reproduction is essential for living organisms to order to:
(a) Keep the individual organism alive
(b) Fulfill their energy requirements
(c) Maintain growth
(d) Continue the species generation after generation
Answer:

Question 15.
Which one of the following permanently marks the end of menstrual cycle in females?
(a) Menarche
(b) Menopause
(c) Ovulation
(d) Pregnacy
Answer:

Question 16.
Which among the following diseases is not sexually transmitted?
(a) Syphillis
(b) Hepatitis
(c) HIV-AIDS
(d) Gonorrhoea
Answer:
(b) Hepatitis

Explanation: Hepatitis is not a sexually transmitted disease. It is a water-borne viral disease.

Question 17.
The sketch of a dicotyledonous seed is shown below.

The correct labelling for parts A, B, C and D iri proper sequence is
(a) radicle, plumule, cotyledon, seed coat.
(b) radicle, plumule, seed coat, cotyledon.
(c) plumule, radicle, cotyledon, seed coat.
(d) plumule, radicle, seed coat, cotyledon
Answer:

Question 18.
Which of the following is not the part of female reproductive system?
(a) ovary
(b) fallopian tube
(c) uterus
(d) vas deferens
Answer:
(d) vas deferens
Explanation: Vas deferens is part of male reproductive system.

Question 19.
Select the statements that are incorrect about reproduction in human beings.
(I) When a girl is born, the ovaries already contain thousands of mature eggs.
(II) One egg is produced every month by one of the ovaries.
(III) The egg is carried from the ovary to the womb through oviduct.
(IV) The two oviducts unite into an elastic bag-like structure known as the cervix.
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)
Answer:

Question 20.
Study the diagram given below of male reproductive organ and select the row containing incorrect information.

Name of Part	Function
(a) P is Vas deferens	Transport sperms
(b) Q is Seminal vesicle	Provide fluid medium to sperms
(c) R is ureter	Passage for sperms
(d) S is Testis	Formation of sperms

Answer:

Question 21.
Study the figure below and identify the row containing incorrect information.

Part Name	Function
(a) A is Cotyledon	It is the future plant
(b) B is Plumule	It is the future shoot
(c) C is Seed coat	It is the outer covering of the ovule
(d) D is Radicle	It is the future root

Answer:
(a) Part Name: A is cotyledon; Function: It is the future plant

Explanation: A is cotyledon and is the food store of the future plant.

Question 22.
Study the figure showing parts of a flower and identify the correct statements.
(I) Part labelled 1 is the pollen grain and contains the male germ cell.
(II) Part labelled 3 is the stigma on which the pollen grains land.
(III) The male germ cell travels through the pollen tube (part labelled 3) after fertilization.
(IV) Part labelled 4 is the ovary which contains the female germ cells.
(a) Both (I) and (III)
(b) Both (II) and (IV)
(c) Both (I) and (III)
(d) Both (I) and (IV)
Answer:

Question 23.
Identify the incorrect statement from among the following statements for unisexual flowers.
(a) They always possess stamen and pistil
(b) They possess either stamen or pistil
(c) They show cross pollination
(d) Unisexualflowers posessing only stamens cannot produce fruits
Answer:
(a) They always possess stamen and pistil

Explanation: Unisexual flowers contain either stamens or carpels. Bisexual flowers contain both male and female reproductive organs stamen and carpel.

Question 24.
The part where fertilization occurs in human females is:
(a) cervix
(b) vagina
(c) uterus
(d) oviduct

Question 25.
The table below lists the organs/parts of human reproductive system and their functions. Identify the row containing incorrect information.

Part/ Organ of Reproductive system	Function
(a) Prostate gland and seminal vesicles	Production of fluid to provide a medium for sperms.
(b) Testis	Secretes the hormone that regulates formation of sperms.
(c) Uterus	Provides nutrition from mother’s blood to embryo.
(d) Fallopian tube	Carries egg from ovaries to the womb

Answer:
(c) Part/Organ of Reproductive system: Uterus; Function: Provides nutrition from mother’s blood to embryo.

Explanation: The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta which is a disc embedded in the uterine wall and contains villi on the embryo’s side of the tissue.

Assertion Reasoning questions Class 10 Science Chapter 8

For the following questions two statements are given-one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is correct explanation of the assertion.
(b) Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 26.
Assertion (A): Variation is useful for the survival of species over time.
Reason (R): Populations of organisms fill well-defined places in the ecosystem, using their ability to reproduce.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of the assertion.

Explanation: Although populations of organisms fill well-defined pLaces in the ecosystem, using their ability to reproduce, the consistency of DNA copying during reproduction. Reproduction is important for the maintenance of body design features. Reproduction is linked to the stability of populations of species.

However, variation is useful for the survival of species over time as niches can change drastically but only those organisms will be able to survive which have some variations in them.

Question 27.
Assertion (A): All multi-cellular organisms can divide cell by cell.
Reason (R): Many multi-cellular organisms are not simply a random collection of cells.
Answer:
(d) (A) is false but (R) is true

Explanation: All multi-cellular organisms cannot simply multiply cell by cell as they are not just a random collection of cells. Specialized cells are organized as tissues and tissues are organized into organs, which occupy definite positions in the body. Multi-cellular organisms, therefore, need to use more complex ways of reproduction.

Question 28.
Assertion (A): Vegetative propagation makes possible propagation of plants that have lost the capacity to produce seeds.
Reason (R): New plants are developed from seeds in vegetative propagation.

Question 29.
Assertion (A): Pollen grains are produced by all flowers.
Reason (R): Stamen is the male reproductive part of a flower and produces pollen grains.
Answer:
(d) (A) is false but (R) is true

Explanation: All flowers do not produce pollen grains as flowers may be unisexual when it contains either stamens or pistil or bisexual when it contains both stamens and pistil. Stamen is the male reproductive part of a flower and produces pollen grains that are yellowish in colour.

Question 30.
Assertion (A): Testes in human males are located outside the abdominal cavity in scrotum.
Reason (R): Testes secrete the male sex hormone testosterone.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of the (A)

Explanation: The testes in human males are located outside the abdominal cavity in the scrotum as sperm formation requires a lower temperature than the normal body temperature. Testes secrete the male sex hormone testosterone which regulates the formation of sperms and brings about changes in appearance seen in boys at the time of puberty.

Question 31.
Assertion (A): The human embryo gets implanted in the fallopian tube.
Reason (R): Embryo gets nutrition from the mother’s blood with the help of special tissue called the Placenta.

Question 32.
Assertion (A): A basic event in reproduction is the creation of a DNA copy.
Reason (R): The DNA in the cell nucleus is the information source for making proteins.

MCQ Questions for Class 10 Science with Answers

Heredity and Evolution Class 10 MCQs Questions with Answers

Question 1.
In peas, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio of pure tall plants to pure short plants in F₂ generation will be:
(a) 1: 3
(b) 3:1
(c) 1:1
(d) 2:1
Answer:
(c) 1:1

Explanation: The genotype ratio of F₂ generation is: TT: Tt: tt = 1: 2: 1. Therefore, the ratio of TT and tt plants of F₂ generation will be the same.

Question 2.
Two pink-colored flowers on crossing resulted in 1 red, 2 pink, and 1 white flower progeny. The nature of the cross will be:
(a) Double fertilization
(b) Self-pollination
(c) Cross-fertilization
(d) No fertilization
Answer:
(c) Cross-fertilization

Explanation: The nature of the cross will be cross fertilization, which is the transfer of pollen from one plant to the stigma of flower; borne on a different plant of the same species.

Related Theory:

• Self-pollination: Transfer of pollen grains from the anther to the stigma of the same flower of the same plant.
• Cross-pollination: Transfer of pollen grains from the anther of one flower to the stigma of another flower.
• Double fertilization: This process occurs when one male nucleus fertilizes (fuses) with the egg cell to form a zygote cell and the other male nucleus fuses (fertilizes) with two polar nuclei to cause triple fusion. These two types of fertilization take place at the same time in the ovule of the plant.

Question 3.
In human males, all the chromosomes are paired perfectly except one. These unpaired chromosomes are:
(I) Large chromosome
(II) Small chromosome
(III) Y chromosome
(IV) X chromosome
(a) (I) and (II)
(b) (III) and (II)
(c) (III) and (IV)
(d) (II) and (IV)
Answer:

Question 4.
Which of the following statement is incorrect?
(a) For every hormone there is a gene.
(b) For every protein there is a gene.
(c) For production of every enzyme there is a gene.
(d) For every molecule of fat there is a gene.
Answer:
(d) For every molecule of fat there is a gene. Explanation: A section of DNA that provides information for one protein is called the gene for that protein. Hormones and enzymes are proteins, and the formation of any particular protein is controlled by a particular gene. Fat biosynthesis occurs through metabolic reaction. They are not related to genes.

Question 5.
Which one is a possible progeny in F2 generation of purebred tall plant with round seed and dwarf plant with wrinkled seeds?
(a) Tall plant with round seeds
(b) Tall plant with wrinkled seeds
(c) Dwarf plant with round seed
(d) All of the above

Question 6.
If a round, green-seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY), the seeds production in the F₁ generation are:
(a) Round and yellow
(b) Round and green
(c) Wrinkled and green
(d) Wrinkled and yellow
Answer:
(a) Round and yellow

Explanation: The cross between RR yy and rr YY seeds will obtain RrYy offspring which will exhibit round and yellow phenotype, as these traits are the dominant ones.

Question 7.
A zygote which has an X chromosome inherited from the father will develop into a:
(a) Boy
(b) Girl
(c) X chromosome does not determine the sex of a child
(d) Either boy or girl
Answer:
(b) Girl

Explanation: Humans follow XX- XY mechanism of sex determination i.e., women are XX while men are XY. All children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus, the sex of the children will be determined by what they inherit from their father. A child who inherits an X chromosome from her father will be a girl and the one who inherits a Y chromosome from him will be a boy.

Question 8.
Select the incorrect statement:
(a) The frequency of certain genes in a population change over several generations resulting in evolution.
(b) The reduction in the weight of an organism due to starvation is genetically controlled.
(c) Low weight parents can have heavy weight progeny.
(d) Traits which are not inherited over generations do not cause evolution.
Answer:

Question 9.
Select the correct statement:
(a) The tendril of a pea plant and the phylloclade of Opuntia are homologous.
(b) The tendril of a pea plant and the phylloclade of Opuntia are analogous.
(c) The wings of birds and the limbs of lizards are analogous.
(d) The wings of bird and the wings of bats are homologous.
Answer:

Question 10.
If the fossil of an organism is found in the deeper layers of earth, then we can predict that:
(a) The extinction of the organism occurred recently.
(b) The extinction of the organism occurred thousands of years ago.
(c) The fossil position in the layers of Earth is not related to its time of extinction.
(d) The time of extinction cannot be deter¬mined.
Answer:
(b) The extinction of the organism occurred thousands of years ago.

Explanation: If we dig into the earth and start finding fossils, the fossils we find closer to the surface are more recent than the fossils we find in deeper layers.

Related Theory
Depth of each stratum signifies the relative age of fossils present in it. The deeper the stratum, the older the rock and the fossils present in it

Question 11.
A trait in an organism is influenced by:
(a) Paternal DNA only
(b) Maternal DNA only
(c) Both maternal and paternal DNA
(d) Neither paternal nor maternal DNA
Answer:
(c) Both maternal and paternal DNA

Explanation: DNA is contributed to an offspring by both the parents; hence, traits are influenced by both maternal and paternal DNA. During sexual reproduction, both mother and father pass their genes to their children, thus determining their traits; or characteristic features.

Question 12.
New species may be formed if:
(I) DNA undergoes significant changes in germ cells.
(II) The chromosome number changes in the gamete.
(III) There is no change in the genetic material.
(IV) Mating does not take place.
(a) (I) and (II)
(b) (I) and (III)
(c) (II), (III) and (IV)
(d) (I), (II) and (III)
Answer:

Question 13.
which of the following statements is not true with respect to variation?
(a) All variations in a species have equal chances of survival.
(b) Change in genetic composition results in variation.
(c) Selection of variants by environmental factors forms the basis of evolutionary processes.
(d) Variation is minimum in asexual reproduction.
Answer:

Question 14.
According to the evolutionary theory, for¬mation of a new species is generally due to:
(a) Sudden creation by nature.
(b) Accumulation of variations over several generations.
(c) Clones formed during asexual reproduction.
(d) Movement of individuals from one habitat to another.
Answer:

Question 15.
The theory of the evolution of species by natural selection was given by:
(a) Mendel
(b) Darwin
(c) Morgan
(d) Lamarck
Answer:

Question 16.
Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution this means that:
(a) Reptiles have evolved from birds.
(b) There is no evolutionary connection between reptiles and birds.
(c) Feathers are homologous structures in both the organisms.
(d) Birds have evolved from reptiles.
Answer:

Question 17.
Select a set of homologous organs from the following:
(a) Wings of a bat and wings of a butterfly
(b) Wings of a pigeon and wings of a bat
(c) Wings of a butterfly and wings of a pigeon
(d) Forelimbs of a duck, forelimbs of a cow and forelimbs of a lizard
Answer:
(d) Forelimbs of a duck, forelimbs of a cow and forelimbs of a lizard

Explanation: Wings of a bat and wings of a butterfly (A), Wings of a pigeon and wings of a bat (B) and Wings of a butterfly and wings of a pigeon (C) are analogous organs as they all use wings for flying but the wings have different structures.

Bat wings consist of flaps of skin stretched between the bones of the fingers and arm, wings of pigeon consist of feathers extending all along the arm whereas butterfly wings are covered in scales.

On the other hand, Forelimbs of a duck, forelimbs of a cow and forelimbs of a lizard are homologous organs as they all have similar structures which have been modified to perform different functions.

Question 18.
Select the correct statements regarding monohybrid cross between a pure tall pea plant and pure short pea plant performed by Mendel:
(I) All plants of the F₁ generation were tall.
(II) The tall plants in the F₁ generation were exactly the same as the tall plants of the parent generation
(III) One-quarter of the F₂ progeny of the F₁ tall plants were short.
(IV) Both the tallness and shortness traits were inherited in the F₁ plants
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (II) and (III)
(d) (I), (III) and (IV)
Answer:
(d) (I), (III) and (IV)

Explanation: When a pure tall pea plant is crossed with a pure short plant, it was observed that all plants of the F₁ generation were tall. But the tall plants in the F₁ generation were not exactly the same as the tall plants of the parent generation. The genotype of the pure tall plant is TT, whereas the genotype of the tall plant in the F₁ generation was Tt. The ratio of the tall and short plants in the F₂ generation was 3:1. As 25 % of the pea plants in the F₂ generation were tall, it means that both the shortness (t) and tallness (T) trait were inherited in the FI plants.

Question 19.
Which of the following are acquired traits?
(I) Attached or free earlobe
(II) Muscular body of a wrestler
(III) Body weight of starving animals
(IV) Brown and curly hair
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
Answer:

Question 20.
Consider the plants the pitcher plant, venus fly trap, poinsettia and cactus.
Select the row containing incorrect information regarding the leaves of these plants in terms of evolutionary relationships.

(a) Leaves of these plants are homol­ogous organs	The leaves are structurally simi­lar but modified to perform differ­ent functions
(b) Leaves of these plants are analo­gous organs	The leaves are structurally dis­similar but per­form similar func­tions
(c) Leaves of these plants are vestig­ial organs	Leaves are ho­mologous    to similar leaves in other plants
(d) Leaves of these plants are neither homologous nor analogous	The leaves have no structural or functional simi­larity

Answer:

Question 21.
Study the organs and evolutionary relationship mentioned alongside. Select the row containing incorrect information.

Organs Relationship	Evolutionary
(a) limbs of human being and frog	Homologous organs
(b) wings of bird and bat	Analogous organs
(c) Thorns and spines in plants	Analogous organs
(d) Tendril of pea plant and grape plant	Homologous organs

Answer:
(d) Organs: Tendril of pea plant and grape plant; Evolutionary Relationship: Homologous organs

Explanation: Thorn is modification of stem and spine is modification of leaf. Tendrils in plant show similar function but they are different in origin. Pea plant has Leaf tendril whears. Grape plant has Stem tendril

Question 22.
which of the statements regarding evolution is correct?
(a) One species is always eliminated in order to give rise to a new species.
(b) The newly formed species are better than the old species.
(c) Evolution is the generation of diversity and the shaping of the diversity by environmental selection.
(d) More and more complex body designs have emerged over time as the older designs are ineffcient.
Answer:

Question 23.
which of the following cannot be an outcome of Mendel’s Experiment on crossing a tall pea plant with a short pea plant?
(a) 3 tall 1 short plant
(b) 4 tall plants and 1 medium height plant.
(c) 24 tall and 8 short plants
(d) 8 tall and 0 short plants
Answer:

Question 24.
Which of the following have a perfect pair of sex chromosomes?
(a) Only Girls
(b) Only Boys
(c) Both girls and boys
(d) It depends on many other factors
Answer:
(a) Only Girls

Explanation: Girls have a perfect paired 23rd chromosome, which is XX, whereas boys have a mismatched 23rd pair of chromosomes, which is XY.

Question 25.
Select the incorrect option.
Genetic drift is:
(a) A mechanism of evolution in which allele frequencies of a population remain constant over generations.
(b) It occurs in all populations of non-infinite size, but its effects are strongest in small populations.
(c) It may result in the loss of some alleles.
(d) It can have major effects when a population is sharply reduced in size by a natural disaster.
Answer:

Question 26.
Select the group which shares the maximum number of common characters:
(a) Two individuals of a species
(b) Two species of a genus
(c) Two genera of a family
(d) Two genera of two families
Answer:

Question 27.
Select the statements that describe the characteristics of genes:
(I) Genes are specific sequence of bases in a DNA molecule.
(II) A gene does not code for proteins.
(III) In individuals of a given species, a specific gene is located on a particular chromosome.
(IV) Each chromosome has only one gene.
(a) (I) and (II)
(b) (I) and (III)
(c) (I) and (IV)
(d) (III) and (IV)
Answer:
(b) (I) and (III)

Explanation: Genes are units of heredity and are responsible for inheritance. Genes control the expression of a trait or a character in an organism. Genes are located on the chromosomes, which is present inside the nucleus of the cell in the crytoplasm.

Question 28.
The number of pair(s) of sex chromosomes in the zygote of humans is:
(a) One
(b) Two
(c) Three
(d) Four
Answer:

Assertion Reasoning questions Class 10 Science Chapter 9

For the following questions, two statements are given: one Labeled Assertion (A) and the other Labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 29.
Assertion (A): The wing of an insect and wing of a bird are analogous organs
Reason (R): The organs which are quite different in fundamental structure and origin but perform the same function in different species are called analogous organs
Answer:

Question 30.
Assertion (A): The sex of a child in human beings will be determined by the type of chromosome he/ she inherits from the father.
Reason (R): A child who inherits ‘X‘ chromosome from his father would be a girl (XX), while a child who inherits a ‘Y‘ chromosome from the father would be a boy (XY).
Answer:
(a) Both (A) and (R) are true and (R) is correct explanation of the (A).

Explanation: Human beings have 23 pairs of chromosomes. Out of which one pair is sex chromosomes and 22 pairs are autosomes. In men, sex chromosome pair is mismatched pair ‘XY‘, ‘X‘ is normal sized and Y is shorter than ‘X‘ chromosomes. Human females have ‘XX chromosomes. Males produce two types of sperms whereas females produce only one ovum having ‘X’ chromosomes. A child who inherits the ‘X’ chromosome from a father would be a girl ‘(XX)’.

While a child who inherits a Y chromosome from the father would be a boy (XY).

Question 31.
Assertion: A geneticist crossed a pea plant having violet flowers with a peaplant with white flowers, he got all violet flowers in first generation.
Reason: White colour gene is not passed on to next generation.
Answer:

Question 32.
Assertion (A): New combination of traits are observed in F₂ offspring when tall plants with round seeds are crossed with short plants with wrinkled seeds.
Reason (R): Tallness and round seed are both dominant traits.
Answer:

MCQ Questions for Class 10 Science with Answers

Human Eye and Colourful World Class 10 MCQs Questions with Answers

Question 1.
A student traces the path of a ray of light through a glass prism for different angles of incidence. He analyses each diagram and draws the following conclusion:
(I) On entering prism, the Lightray bends towards its base.
(II) light ray suffers refraction at the point of incidence and point of emergence while passing through the prism.
(III) Emergent ray bends at a certain angle to the direction of the incident ray.
(IV) White emerging from the prism, the Lightray bends towards the vertex of the prism.
Out of the above inferences, the correct ones are:
(a) (I), (II) and (III)
(b) (I), (III) and (IV)
(c) (II), (III) and (IV)
(d) (I) and (IV)
Answer:
(a) (I), (II) and (III)

Related Theory:
In a prism, the ray of light from air into glass bends towards the normal. The ray of light from glass to air bends away from the normal. In both cases, when a ray of light passes through a prism, it bends towards the base of the prism.

Question 2.
A clear sky appears blue, because:
(a) blue light gets absorbed in the atmosphere
(b) ultraviolet radiations are absorbed in the atmosphere
(c) violet and blue lights get scattered more than the lights of all other colours by the atmosphere
(d) lights of all other colours are scattered more than the violet and blue colour lights by the atmosphere
Answer:

Question 3.
Which of the following statements is correct regarding the propagation of light of different colours of white light in the air?
(a) Red light moves the fastest.
(b) Blue light moves faster than green light.
(c) All the colours of the white light travel at the same speed.
(d) Yellow light moves with the mean speed as that of red and violet light.
Answer:

Question 4.
In the following diagram, the correctly marked angles are:

(a) All
(b) Only ∠i, and ∠A
(c) ∠i, ∠r and ∠A
(d) ∠i, ∠A and ∠D
Answer:

Question 5.
The bluish colour of water in deep sea is due to:
(a) the presence of algae and other plants found in water
(b) reflection of the sky in water
(c) scattering of light
(d) absorption of light by the sea
Answer:
(c) scattering of light

Explanation: The bluish colour of water in deep sea is due to scattering of light. The fine particles in water scatter mainly blue light having shortest wavelength.

Related Theory
Water appears blue because when white light from the Sun falls on the water molecules, only blue light is reflected and scattered and reaches our eyes.
The absorption of light by a molecule depends on the wavelength and the size of the molecule. A molecule absorbs light of a wavelength either equal to or greater than the order of the size of the object.
Since red, orange and yellow have longer wavelengths, they are absorbed by the water molecules, whereas blue, having a shorter wavelength, is scattered.

Question 6.
During the experiment, to trace the path of ray of light through the glass prism, students reported the following observations:
(I) The ray of light from air to glass at the first refracting surface bends away from the normal after refraction.
(II) At the second refracting surface, light rays entered from air to glass.
(III) Lightray suffers two refractions on passing through a prism and in each refraction it bends towards the base of the prism.
(IV) Lightray suffers two refractions on passing through a prism. In first refraction, it bends away from the normal while in the second refraction it bends towards the normaL
The correct observation is/are:
(a) (I) and (II) only
(b) (III) only
(c) (II) and (IV) only
(d) (I) and (IV) only
Answer:

Question 7.
In an experiment to trace the path of a ray of light through a triangular glass prism, a student would observe that the emergent ray
(a) is parallel to the incident ray.
(b) is along the same direction of incident ray.
(c) gets deviated and bends towards the thinner part of the prism.
(d) gets deviated and bends towards the thicker part (base) of the prism.
Answer:

Question 8.
In the following ray diagram the correctly marked angle are:

(a) ∠i, and ∠e
(b) ∠A and ∠D
(c) ∠i, ∠e and ∠D
(d) ∠r, ∠A and ∠D
Answer:
(d) ∠r, ∠A and ∠D

Question 9.
A person cannot see distinctly the objects kept beyond 2 m. This defect can be corrected by using a lens of power:
(a) + 0.5 D
(b) – 0.5 D
(c) + 0.2 D
(d) – 0.2 D
Answer:

Question 10.
A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct?
(a) The near point of his eyes has receded away.
(b) The near point of his eyes has come closer to him.
(c) The far point of his eyes has come closer to him.
(d) The far point of his eyes has receded away.
Answer:
(a) The near point of his eyes has receded away.

Explanation: The student can see the object which is far from him but can’t see nearby objects. It means that the near point of his eyes has receded away. This condition is known as hypermetropia or farsightedness.

Question 11.
When light rays enter the eye, most of the refraction occurs at the:
(a) crystalline lens
(b) the outer surface of the cornea
(c) iris
(d) pupil
Answer:
(b) the outer surface of the cornea

Explanation: Light enters the eye through a thin membrane called the cornea. It causes most of the bending of incident light rays, i.e. refraction, to make them converge which in turn causes image formation on the retina.

Question 12.
The focal length of the eye lens increases when eye muscles:
(a) are relaxed and the lens becomes thinner
(b) contract and the lens becomes thicker
(c) are relaxed and the lens becomes thicker
(d) contract and the lens becomes thinner
Answer:

Question 13.
Which of the following statements is correct?
(a) A person with myopia can see distant objects clearly.
(b) A person with hypermetropia can see nearby objects clearly.
(c) A person with myopia can see nearby objects clearly.
(d) A person with hypermetropia cannot see distant objects clearly.
Answer:
(c) A person with myopia can see nearby objects clearly.

Explanation: Myopia is also termed as short-sightedness. A person suffering from myopia can see nearby objects clearly but not the distant objects. Whereas hypermetropia is termed as long-sightedness. A person suffering from hypermetropia can see distant objects clearly but not the nearby objects.

Question 14.
Person suffering from cataract has:
(a) elongated eyeball
(b) excessive curvature of eye lens
(c) weakened ciliary muscles
(d) opaque eye Lens
Answer:

Question 15.
When we enter a dark room coming from outside, immediately the things inside the room do not appear clear to our eyes. This is because:
(a) pupils do not open at all in the dark.
(b) pupils take time to adjust.
(c) light travels slower in a dark room.
(d) pupils open very quickly in the dark.
Answer:

Question 16.
The phenomena of light responsible for the working of the human eye is:
(a) reflection
(b) refraction
(c) power of accommodation
(d) persistence of vision
Answer:

Question 17.
The sky appears dark to passengers flying at very high altitudes mainly because:
(a) Scattering of light is not enough at such heights.
(b) There is no atmosphere at great heights.
(c) The size of molecules is smaller than the wavelength of visible light.
(d) The light gets scattered towards the earth.
Answer:
(a) Scattering of light is not enough at such heights.

Explanation: At higher altihide either the atmospheric medium is very rare or there are no particles present/ no atmosphere, thus the scattering of light taking place is not enough at such heights or no scattering of sunlight takes place. Hence, the sky appears dark to the passengers flying at very high altitude.

Question 18.
Given below are some common observations related to optics. Select the row containing incorrect observations and its reason.

Observation	Reason
(a) Colour of water in deep sea	Scattering of light
(b) Apparent position of stars	Atmospheric refraction
(c) Fishes appear higher than their actual depth	Diffraction of light
(d) Spectrum seen on soap bubbles	Dispersion of light

Answer:
(c) Observation: Fishes appear higher than their actual depth, Reason: Diffraction of light

Explanation: Fishes appear higher than their actual depth due to the refraction of light as light travels from water, an optically denser medium, to air, a rarer medium. Diffraction of light refers to the phenomena of bending of light around corners.

Question 19.
The defective eye of a person has near point 0.5 m and far point 75 cm. The table below lists the type of corrective lens and its power required for reading purposes and for seeing distant objects.

Select the row containing the correct information:

For reading purpose	For seeing distant objects
(a) Concave lens of  power – 0.5 D	Convex lens of power + 0.75 D
(b) Convex lens of power +0.5 D	A concave lens of power – 0.75 D
(c) Convex Lens of power + 0.5 D	Concave Lens of power-1.33 D
(d) Convex Lens of power + 2.0 D	Concave Lens of power -1.33 D

Answer:

Question 20.
A 55 year old near-sighted person wears spectacles with a power of – 2.5 D for distance viewing. His doctor prescribes a correction of + 2.0 D in the near-vision section of his bifocals. This is measured relative to the main part of the lens.

Select the correct statements:
(I) The focal length of the distance-viewing part of the lens is – 40 cm.
(II) The focal length of the near-vision part of the lens is + 50 cm.
(III) The focal length of the distance-viewing part of the lens is + 50 cm.
(IV) The focal length of the near-vision part of the lens is – 40 cm.
(a) Both (I) and (II)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (III) and (IV)
Answer:

Question 21.
A beam of white light falling on a glass prism gets split up into seven colours marked 1 to 7 as shown in the diagram
Select the incorrect statements regarding the colours marked from 1 to 7:
(I) The colour at position marked 7 and 5 are similar to the colour of the blood and colour of gold metal respectively.
(II) The colour at position marked 1 and 3 are similar to the colour of the blood and colour of gold metal respectively.
(III) The colour at position marked 3 and 4 are similar to the colour of the sky and colour of leaves in plants respectively.
(IV) The colour at position marked 5 and 4 are similar to the colour of the sky and colour of leaves in plants respectively.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (II) and (IV)
Answer:

Question 22.
The defects of vision hypermetropia and myopia can be corrected by:
(a) Concave and a plano-convex lens
(b) Concave and convex lens
(c) Convex and concave lens
(d) Plano-concave lens for both defects.
Answer:
(c) Convex and concave lens

Explanation: Hypermetropia or far sightedness can be corrected by using convex lens of appropriate power and myopia by a concave lens of appropriate power.

Question 23.
The layer of atmosphere whose temperature is less than that of the hotter layer behaves as an optically
(a) denser medium
(b) rarer medium
(c) inactive medium
(d) either denser or rarer medium
Answer:
(a) denser medium

Explanation: The layer of atmosphere whose temperature is less than that of hotter layer is more denser as compared to the hotter layer of the atmosphere. So, when light travels from a cooler layer of atmosphere to a hotter Layer, it will bend away from the normal.

Question 24.
The sun appears white at noon as:
(a) Blue colour is scattered the most
(b) Red colour is scattered the most
(c) Light is least scattered
(d) All the colours of the white light are scattered away
Answer:

Assertion Reasoning questions Class 10 Science Chapter 11

For the following questions, two statements are given-one tabled Assertion (A) and the other labeled Reason (R) select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below: ,
(a) Both (A) and (R) are true and (R) is correct explanation of the (A).
(b) Both (A) and (R) are true but (R) is not correct explanation of the (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 25.
Assertion (A): Sky appears in blue colour.
Reason (R): Blue colour in sunlight travelling through atmosphere undergoes maximum scattering.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).

Explanation: The blue colour of the sky is due to the scattering of blue colour to the maximum extent by dust particles. The blue colour appears to be coming from the sky. Blue colour has the least wavelength. Hence, the correct option is (a).

Question 26.
Assertion (A): When white light passes through a glass prism, red colour has deviated the least.
Reason (R): Red colour has the minimum speed in the glass prism.
Answer:
(c) (A) is true but (R) is false.

Explanation: When white light passes through a glass prism, red colour deviates the least because red colour has maximum speed in the prism.

Question 27.
Assertion (A): When objects are observed through hot air, they appear to be moving slightly.
Reason (R): Hotter air is optically denser and the cooler air is optically rarer.
Answer:

Question 28.
Assertion (A): A rainbow is always formed in the sky after a rain shower and in the same direction as the sun.
Reason (R): Water droplets act as tiny prisms.
Answer:
(d) (A) is false but (R) is true.

Explanation: A rainbow is always formed in the sky in a direction opposite to that of the sun. The water droplets present in the sky act as tiny prisms, which refract and disperse sunlight, then reflect it internally and finally refract it again when it comes out of the raindrop.

Question 29.
Assertion (A): The sun’s disc appears to be flattened at sunrise and sunset.
Reason (R): The sun is near the horizon at sunrise and sunset and sunlight suffers atmospheric refraction.
Answer:

MCQ Questions for Class 10 Science with Answers

Electricity Class 10 MCQs Questions with Answers

Question 1.
The values of mA and µA are:
(a) 10^-6 and 10^-9 A respectively
(b) 10^-3 and 10^-6 A respectively
(c) 10^-3 and 10^-9 A respectively
(d) 10^-6 and 10^-3 A respectively
Answer:
(b) 10^-3 A and 10^-6 A.

Explanation: An ampere is the SI unit of electric current
1A = 1000mA Or 1mA = \(\frac{1 \mathrm{~A}}{1000}\) = 10³A

∴ 1 µA = 10^-3 × 10^-3 A = 10^-6A

Question 2.
A cylindrical conductor of Length ‘l’ and uniform area of cross-section ‘A’ has resistance ‘R’. Another conductor of Length 2.5 1 and resistance 0.5 R of the same material has area of cross-section.
(a) 5A
(b) 2.5A
(c) 0.5A
(d) \(\frac{1}{5}\) A

Question 3.
Identify the circuit in which the electrical components have been properly connected.

(a) (I)
(b) (II)
(c) (III)
(d) (IV)
Answer:
(b) (II)

Explanation: In figure (I), the voltmeter is connected in series (not parallel). Similarly, in figure (III). the ammeter ¡s in parallel which should be in series. In figure (IV), the negative terminal of battery has been connected to the positive terminal of the ammeter, whereas it should be connected to the negative terminal

Related Theory:
Essential conditions when components connected:

• The voltmeter should be connected in parallel
• The ammeter should be connected in series.
• Positive terminals of the voltmeter arid ammeter should be connected to the positive terminal of the cell and their negative removals should be joined to the negative terminal of the cell

Question 4.
If a person has five resistors each of value Ω, then the maximum resistance he can obtain by connecting them ¡s:
(a)1 Ω
(b)5 Ω
(c) 10 Ω
(d) 25 Ω
Answer:

Question 5.
What is the minimum resistance which can be made using five resistors, each of \(\frac{1}{5}\) Ω?
(a) \(\frac{1}{5}\) Ω
(b) \(\frac{1}{25}\) Ω
(c) \(\frac{1}{10}\) Ω
(d) 25 Ω
Answer:

Question 6.
The resistance of a resistor is reduced to half of its initial value. In doing so, if other parameters of the circuit remain unchanged, the heating effects in the resistor will become:
(a) two times
(b) half
(c) one-fourth
(d) four times
Answer:
(a) two times

Explanation: Resistance of a resistor R Q New resistance of a resistor Q

All other parameters of the circuit remain unchanged

By applying Joule’s law of heating H = I2Rt

As per Ohms Law V = IR Or I = \(\frac{V}{R}\)

Hence, the heating effect in the resistor will become two times if all other parameter of the circuit remain same.

Question 7.
At the time of short circuit, the electric current in the circuit:
(a) vary continuously
(b) does not change
(c) reduces substantially
(d) increases heavily
Answer:

Question 8.
Two bulbs of 100 Ω and 40 Ω are connected in series. The current through the 100 Ω bulb is 1 A. The current through the 40 Ω bulb will be:
(a) 0.4 A
(b) 0.6 A
(c) 0.8 A
(d) 1A
Answer:
(d) 1 A

Explanation:

In a series combination of resistors (bulbs) the current is the same in every part of the circuit as current does not change in series combination so both the bulbs get equal amount of current Hence the current through the 40 Ωbulb will be 1A.

Question 9.
When a 4 V battery is connected across an unknown resistor there is a current of 100 mA in the circuit. The value of the resistance of the resistor is:
(a) 4 Ω
(b) 40 Ω
(c) 400 Ω
(d) 0.4 Ω
Answer:
(b) 40 Ω
V = IR, V = 4 V,
I = 100 mA = 0.1 A
Hence R = \(\frac{V}{1}=\frac{4}{0.1}\) Ω = 40 Ω.

Question 10.
The equivalent resistance of a series combination of two resistances is X Ohm. If the resistance are of 10 Ohm and 40 Ohm respectively, the value of X will be:
(a) 10 Ohm
(b) 20 Ohm
(c) 50 Ohm
(d) 40 Ohm [Diksha]
Answer:

Question 11.
Unit of electric power may also be expressed as:
(a) volt-ampere
(b) kilowatt-hour
(c) watt-second
(d) joule-second
Answer:

Question 12.
if the resistance of a certain copper wire is 1 Ω, then the resistance of a similar nichrome wire will be about:
(a) 25 Ω
(b) 30 Ω
(c) 60 Ω
(d) 45 Ω
Answer:
(c) 60 Ω

Explanation: if the resistance of a certain copper wire is 1 Ω, the resistance of a similar nichrome wire will be about 60 Ω because the resistivity of nichrome is 60 times the resistivity of copper.

Question 13.
The resistivity of a certain material is 0.6 Ω m, The material is most likely to be:
(a) an insulator
(b) a superconductor
(c) a conductor
(d) a semiconductor
Answer:

Question 14.
A cell, a resistor, a key, and an ammeter are arranged as shown in the circuit diagrams of the figure. The current recorded in the ammeter will be:

(a) Maximum in (I)
(b) Maximum in (II)
(c) Maximum in (III)
(d) The same in all the cases
Answer:
(d) The same in all the cases

Explanation: In series connections, the order of elements in the circuit will not affect the amount of current flowing in the circuit.

Question 15.
The instrument used for measuring electric current is:
(a) galvanometer
(b) ammeter
(c) voltmeter
(d) potentiometer
Answer:

Question 16.
A student plots V-l graphs for three samples of nichrome wire with resistances R1, R2 and R3. Choose from the following the statement that holds true for this graph.

(a) R₁ = R₂ = R₃
(b) R₁ > R₂ > R₃
(c) R₃ > R₂ > R₁
(d) R₂ > R₁ > R₃
Answer:
(d) R₂ > R₁ > R₃

Explanation: As is clear from the graph, the current for A₂ conductor is less than A₁ and A₁ is Less than A₃. We can say IA₂ < IA₁ < IA₃
R₂ > R₁ > R₃ (AS, R = V)

Question 17.
The maximum resistance which can be made using four resistors each of resistance \(\frac{1}{2}\) Ω is:
(a) 2 Ω
(b) 1 Ω
(c) 2.5 Ω
(d) 8 Ω
Answer:
(a) 2 Ω

Explanation: When a number of resistances are connected in series the resultant resistance is equal to the sum of the individual resistances and is greater than any individual resistance. Four resistors are given:

Hence, the maximum resistance which can be made using four resistors each of resistance \(\frac{1}{2}\) Ω is 2 Ω.

Question 18.
A current of 2 A is drawn by a conductor on applying a potential difference of 6 V across its ends. The number of electrons passing through a cross-section of the conductor and the heat generated in the conductor in 8 seconds is:

Number of Electrons Passing in 8 s	Heat Generated in 8 s
(a) 1.6 × 10-20	24 J
(b) 1020	96 J
(c) 1.28 × 10-18	3.6 × 106 J
(d) 1030	96 J

Answer:

Question 19.
The resistivity of four wires A, B, C, and D are of the order of 10¹², 10^-6, 10^-8, and 10¹⁴ respectively. !f the wires are of equal lengths and equal areas of cross-section, then select the row containing the correct information:

Resistance	Nature
(a) Resistance of C will be the least	C is the conductor best of electricity
(b) Resistance of A will be the largest	A is a good conductor of electricity
(c) Resistance of B will be the largest	B is a poor conductor of electricity
(d) Resistance of D will be the least	D is the conductor best of electricity

Answer:

Question 20.
Given below are four statements on-resistance of a conductor. Select the incorrect statements:
(I) If in an electric circuit, the resistance is doubled the voltage also gets doubled.
(II) If in an electric circuit, the resistance is halved the current gets doubled.
(III) Variable resistance is a component used to regulate voltage without changing the current.
Answer:
(b) Both (I) and (III)

Explanation: According to Ohm’s law, V = IR.
Therefore, l = \(\frac{V}{R}\).

It means that if resistance R is doubled, the current gets halved, but the voltage remains the same. Similarly, if resistance is halved, currently gets doubled.

Question 21.
Given below are four statements about resistivity. Select the incorrect statements:
(I) Resistivity is a characteristic property of the material and varies with temperature.
(II) Resistivity depends on the length and area of the cross-section of the conductor.
(III) Metals and alloys have very low resistivity and are good conductors of electricity.
(IV) Insulators have low resistivity of the order of 10¹² to 10¹⁷ Ohm.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (II) and (iV)
Answer:

Question 22.
Select the correct statements from the statements given below:
(I) In a parallel circuit the current is constant throughout the electric circuit.
(II) In a parallel circuit the other components keep working even if one component fails.
(III) In a series circuit when one component fails, the circuit is broken and the other components stop working.
(IV) in a series circuit, the current is divided among the electrical gadgets depending upon their resistance.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) (I), (III), and (IV)
Answer:
(b) Both (II) and (III)

Explanation: In a series circuit, the current is constant through the electric circuit and if one component fails, the other components also stop working. Whereas in a parallel circuit, the current is divided among the different components depending upon their resistance, and if one component fails, the other components keep working.

Question 23.
The unit of potential difference is:
(a) JC
(b) J/C
(c) J
(d) C/J
Answer:
(b)J/C

Explanation: Potential difference between two points in an electric field of a given charge is defined as the work done in moving a unit positive charge from one point to another. As V = \(\frac{W}{q}\) , the unit of potential difference is Joule/ Coulomb or J/C.

Question 24.
If both the length of a conductor and its radius is doubled, the ratio of new resistance and original resistance will be:
(a) 1:1
(b) 2:1
(c) 4:1
(d) 1: 2
Answer:

Question 25.
When a 2 Ω resistor is connected across the terminals of a 6 V battery, the charge (in coulombs) passing through the resistor per second is:
(a) 0.5
(b) 2
(c) 3
(d) 4
Answer:
(c) 3

Explanation: The charge passing through a resistor per second is the same as the current passing through the resistor since current is defined as the rate of flow of charges. The current flowing is found by using Ohm’s law, V = IR. Therefore, I = V/R = 6/2 = 3A, which is the same as the charge passing in one second.

Question 26.
A battery of 6V is connected in series with resistors of 0.1 ohms, 0.2 ohms, 0.3 ohms, 0.4 ohm,s and 2 ohms. How much current would flow through the 0.3-ohm resistor?
(a) 0.895A
(b) 1.2 A
(c) 2 A
(d) 3 A

Assertion Reasoning questions Class 10 Science Chapter 12

For the following questions, two statements are given – One labeled Assertion (A) and the other labeled Reason (R), select the correct answer to these questions from the codes (a), (b), (c), and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of the (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 27.
Assertion (A): At high temperatures, metal wires have a greater chance of short-circuiting.
Reason (R): Both resistance and resistivity of a material vary with temperature.
Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of the (A).

Explanation: At high temperatures, the free electrons start moving at a greater speed and more heat is evolved. The increased amount of heat melt the insulation of wires and wires have a greater chance of short-circuiting. Sometimes the short circuit may even melt the wire and it may cause fire.

Both resistance and resistivity vary with temperature. When the temperature is increased, the random motion of electrons increases. As a result the number of collisions increases between atoms and electrons.

Question 28.
Assertion (A): When two ends of a metallic wire are connected across the terminals of a cell, then some potential difference is set up between its ends. The direction of electrons are from a positive terminal to negative terminal of the cell.
Reason (R): Electrons are flowing through the conductors from its higher potential to its lower potential end. [Diksha]
Answer:

Question 29.
Assertion: A fuse wire is always connected in parallel with the mainline.
Reason: If a current larger than the specified value flows through the circuit, fuse wire melts.
Answer:

Question 30.
Assertion(A): Electric appliances with the metallic body have three pin connection, whereas an electric bulb has a two pin connection.
Reason (R): Three pin connection reduce heating of connecting wires. [Diksha]
Answer:
(c) (A) is true but (R) is false.

Explanation: The three connection of electric appliances with metallic body are live wire, neutraL wire and earth wire. The live and neutraL wire supply electric current to the appliance, whereas the earth wire, which is connected to the metal body of the electric appliance, protects us from electric shock in case we touch the metal body of appliances.

In case of an electric shock, the current passes directly to the earth through the earth wire and we do not feel the electric shock.

On the contrary, three-pin connection do not reduce heating of connecting wires.

Question 31.
Assertion (A): In a purely resistive circuit, the source energy is dissipated in the form of heat.
Reason (R): The potential difference across the ends of a conductor is directly proportional to the current flowing through it.
Answer:

Question 32.
Assertion (A): Alloys are commonly used in electrical heating devices like electric ion and heater.
Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points then their constitutent, metals. [CBSE 2020]
Answer:
(a) Both (A) and (R) are true and (R) is correct explanation of the assertion.

Related Theory
Alloys have more resistivity than of its constituent elements because alloys have better properties than that of metals. Resistivity is the property of a material that explains how strongly the material opposes flow of electrons. Higher the resistivity, smaller will be the conductivity i.e. why alloys are used in electrical heating devices.

Metals have a higher melting point as the atoms are arranged in a regular manner and form a strong bond whereas alloys are made up of different metals. The different sizes of atoms in an alloy make their arrangement less regular than a pure metal. This makes the bonds between the atoms weaker and lowers the melting point.

MCQ Questions for Class 10 Science with Answers

Sources of Energy Class 10 MCQs Questions with Answers

Question 1.
Which of the following is a non-renewable source of energy?
(a) Wood
(b) Sun
(c) Fossil fuels
(d) Wind
Answer:
(c) Fossil fuels

Explanation: Non-renewable sources are those sources that are present in a limited amount and once finished cannot be renewed again for millions of years.

Wood comes from trees, so it is a renewable source of energy. The Sun and wind are also renewable sources of energy but fossil fuels are non-renewable (conventional sources). Once they are used up, they can’t be renewed again, so we need to conserve them.

Question 2.
In a hydropower plant:
(a) the potential energy possessed by stored water is converted into electricity
(b) the kinetic energy possessed by stored water is converted into potential energy
(c) electricity is extracted from water
(d) water is converted into steam to produce electricity
Answer:

Question 3.
Ocean thermal energy is due to:
(a) energy stored by waves in the ocean
(b) temperature difference at different levels in the ocean
(c) pressure difference at different levels in the ocean
(d) tides arising in the ocean
Answer:

Question 4.
The major probLem in harnessing nuclear energy is how to:
(a) split nuclei?
(b) sustain the reaction?
(c) dispose off spent fuel safely?
(d) convert nuclear energy into electrical energy?
Answer:

Question 5.
Which part of the solar cooker is responsible for the greenhouse effect?
(a) Coating with black coLour inside the box
(b) Mirror
(c) Glass sheet
(d) Outer cover of the solar cooker
Answer:
(c) Gloss sheet

Explanation: Sotar cookers are covered with a glass plate which traps infrared radiations (heat) from sunlight and does not allow them to escape. In other words, we can say that it provides a greenhouse effect. Solar cookers achieve a higher temperature by using mirrors to focus the rays of the Sun.

Related Theory

The trapping of heat in the environment due to the presence of greenhouse gases like CO₂, methane, water vapour etc. causes the greenhouse effect. This raises the temperature of Earth.

Question 6.
The main constituent of biogas is:
(a) methane
(b) carbon dioxide
(c) hydrogen
(d) hydrogen sulfide
Answer:
(a) methane

Explanation: Biogas is an excellent fuel as it contains up to 75% methane. It burns without smoke, leaves no residue like ash in wood. charcoal and coal burning. Its heating capacity is high. It is also used for lighting.

Question 7.
The power generated in a windmill:
(a) is more in the rainy season, since damp air would mean more air mass hitting the blades
(b) depends on the height of the tower
(c) depends on wind velocity
(d) can be increased by planting tall trees close to the tower
Answer:

Question 8.
Choose the correct statement:
(a) The Sun can be taken as an inexhaustible source of energy
(b) There is infinite storage of fossil fuel inside Earth
(c) Hydro and wind energy plants are non-polluting sources of energy
(d) Waste from a nuclear power plant can be easily disposed off
Answer:

Question 9.
In a hydroelectric power plant, more electrical power can be generated if waterfalls from a greater height because:
(a) its temperature increases
(b) larger amount of potential energy is converted into kinetic energy
(c) the electricity content of water increases with height
(d) more water molecules dissociate into ions
Answer:

Question 10.
The biggest source of energy on Earth’s surface is:
(A) Biomass
(B) Solar radiations
(C) Tides
(D) Winds
Answer:

Question 11.
Which is the type of system where the energy is harnessed by the heat accumulated on the surface of the water?
(a) Wind energy
(b) Wave energy
(c) Ocean thermal energy conversion
(d) Solar energy
Answer:
(c) Ocean thermal energy conversion

Explanation: Absorption of heat from the sun by the seas and oceans, solar radiation causes ocean currents and moderate temperature gradients from the water surface downward especially in tropical waters.

Question 12.
The correct energy conversion taking place in a hydroelectric power plant is:
(a) Potential energy of water → Kinetic Energy of turbine → Electrical energy
(b) Potential energy of turbine → Kinetic Energy of water → Electrical energy
(c) Heat energy of water → Kinetic Energy of turbine → Electrical energy
(d) Potential energy of water → Heat Energy → Electrical energy
Answer:

Question 13.
Which of the following are non-conventional sources of energy:
(I) Wind energy
(II) Water
(III) Solar energy
(IV) Geothermal energy
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (II) and (IV)
Answer:

Question 14.
Approximately what percentage of energy requirement in India is met by hydropower plants?
(a) 10 %
(b) 25 %
(c) 50 %
(d) 75 %
Answer:
(b) 25 %

Explanation: A quarter or 25 % of the energy requirement in India is met by hydropower plants. But we are still largely dependent upon coal and petroleum for meeting our energy requirements.

Question 15.
The table below lists the sources of energy and whether they are exhaustible or non-exhaustible. Select the row containing incorrect information:

Source of energy	Whether exhaustible or non- exhaustible
(a) Fossil fuel	Exhaustible
(b) Wind	Non-exhaustible
(c) Water	Exhaustible
(d) Solar	Non-exhaustible

Question 16.
Two fuels obtained from biomass are:
(a) Coal and biogas
(b) Petroleum and natural gas
(c) Charcoal and biogas
(d) Charcoal and natural gas
Answer:
(c) Charcoal and biogas

Explanation: When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the residue. Charcoal burns without flames is comparatively smokeless and has a higher heat generation efficiency. Similarly, cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give biogas.

Assertion Reasoning questions Class 10 Science Chapter 14

For the following questions, two statements are given one labeled Assertion (A) and the Other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 17.
Assertion (A): In a wind energy farm, a number of windmills are erected over a large area.
Reason (R): The output of a single windmill is quite small and cannot be used for commercial purposes.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.

Question 18.
Assertion (A): All exhaustible sources of energy are non-renewable.
Reason (R): Energy sources that cannot be regenerated are called renewable sources of energy.
Answer:

MCQ Questions for Class 10 Science with Answers