CBSE Class 10 Science Sample Paper 2023-24

1.Identify ‘p’, ‘q’ and ‘r’ in the following balanced reaction
Heat
p Pb (NO3)2(s) ——> q PbO(s) + r NO2(g) + O2(g)
A. 2,2,4
B. 2,4,2
C. 2,4,4
D. 4,2,2

Ans: A. 2,2,4

2.Match column I with column II and select the correct option using the given
codes.
Column I Column II
a. A metal that forms amphoteric oxides (i) Ga
b. A metal which melts when kept on our palm (ii) Au
c. A metal that reacts with nitric acid (iii) Al
d. A metal which cannot displace hydrogen from
acids (iv) Mn

A. a – (ii), b – (i), c – (iii), d – (iv)
B. a – (iii), b – (i), c – (iv), d – (ii)
C. a – (iv), b – (ii), c – (iii), d – (i)
D. a – (iii), b – (ii), c – (i), d – (iv)

Ans: B. a – (iii), b – (i), c – (iv), d – (ii)

4.An aqueous solution ‘A’ turns the phenolphthalein solution pink. On addition of
an aqueous solution ‘B’ to ‘A’, the pink colour disappears. Which of the following
statement is true for the solutions ‘A’ and ‘B’.
A. A is strongly basic and B is a weak base.
B. A is strongly acidic and B is a weak acid.
C. A has a pH greater than 7 and B has a pH less than 7.
D. A has a pH less than 7 and B has a pH greater than 7.

Ans: C. A has a pH greater than 7 and B has a pH less than 7

5 .When 50g of lead powder is added to 300 ml of blue copper sulphate
solution, after a few hours, the solution becomes colourless. This is an
example of
A. Combination reaction
B. Decomposition reaction
C. Displacement reaction
D. Double displacement reaction

Ans: C. Displacement reaction

6. The electronic configuration of three elements X, Y and Z are X- 2, 8, 7; Y- 2,
8, 2; and Z – 2, 8
A. Y and Z are metals
B. Y and X are non-metals
C. X is a non -metal and Y is a metal
D. Y is a non-metal and Z is a metal

Ans: C. X is a non-metal and Y is a metal.

7 .Which of the following is an endothermic reaction?
A. Burning of candle.
B. Cooking of food.
C. Decomposition of Vegetable matter.
D. Reaction of Sodium with air

Ans: B. Cooking of food

8. During cellular oxidation of Glucose, ATP is produced along with formation of
other products in this reaction. Which of the following events is associated with
production of maximum ATP molecules per molecule of Glucose during this
process? Synthesis of
A. ethanol in yeast
B. lactic acid in muscle cells
C. carbon dioxide in yeast cells
D. carbon dioxide in human cells

Ans: D. carbon dioxide in human cells

9. During which of the following stages of the circulation of blood in a normal
human being, the oxygenated blood is pumped to all parts of the body?
A. contraction of the left atrium
B. contraction of left ventricle
C. relaxation of the right atrium
D. relaxation of the right ventricle

Ans: B. contraction of left ventricle.

10. Which of the following adaptations in herbivores helps in digestions of
cellulose?
A. Longer large intestine
B. Smaller large intestine
C. Smaller small intestine
D. Longer small intestine

Ans: D. Longer small intestine.

11 .There was a cerebellar dysfunction in a patient. Which of the following activities
will get disturbed in this patient as a result of this?
A. Salivation
B. Hunger control
C. Posture and balance
D. Regulation of blood pressure

Ans: C. Posture and balance.

12. In snails individuals can begin life as male and depending on environmental
conditions they can become female as they grow. This is because
A. male snails have dominant genetic makeup.
B. female snails have dominant genetic makeup.
C. expression of sex chromosomes can change in a snail’s life time.
D. sex is not genetically determined in snails.

Ans: D. sex is not genetically determined in snails.

13. In the following cases, a ray is incident on a concave mirror. In which case
is the angle of incidence equal to zero?
A. A ray parallel to the principal axis.
B. A ray passing through the centre of curvature and incident obliquely.
C. A ray passing through the principal focus and incident obliquely.
D. A ray incident obliquely to the principal axis, at the pole of the mirror.

Ans: B. A ray passing through the centre of curvature and incident obliquely.

15. Identify the incorrect statement
‘The energy available to the producers is maximum’ because:
A. It is the first trophic level which absorbs1% of light energy directly from
the source.
B. It utilizes the most of the chemical energy for its own respiration, growth,
reproduction, movement etc.
C. It utilizes 10% of light energy and transfers the rest to the next trophic
level.
D. It transfers only 10% of light energy to the next trophic level.

Ans: C. It utilizes 10% of light energy and transfers the rest to the next trophic
level

16. Which of the following is not a role of decomposers in the ecosystem?
A. Natural replenishment of soil.
B. Enrichment of oxygen in atmosphere.
C. Waste decomposition.
D. Break-down of dead remains.

Ans: B. Enrichment of oxygen in the atmosphere.

Question No. 17 to 20 consist of two statements – Assertion (A) and Reason (R). Answer
these questions by selecting the appropriate option given below:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, and R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true
17 .Assertion (A): On adding dil. HCl to a test tube containing a substance ‘X’, a
colourless gas is produced which gives a pop sound when a burning match
stick is brought near it.
Reason (R): In this reaction metal ‘X’ is displaced by Hydrogen.

Ans: C. A is true but R is false

18. Assertion (A): Generally, the number of chromosomes in a cell and in a germ
cell is not the same in species.
Reason (R): When two germ cells combine, they restore the normal number of
chromosomes in a species.

Ans: A. Both A and R are true, and R is the correct explanation of A.

19. Assertion (A): A convex mirror always forms an image behind it and the image
formed is virtual.
Reason (R): According to the sign convention, the focal length of a convex
mirror is positive.

Ans: B. Both A and R are true, and R is not the correct explanation of A

20. Assertion (A): If the lions are removed from a food chain it will not affect the
food chain, however if the plants are removed from a food chain it will disturb
the ecosystem.
Reason (R): Plants are producers who can make food using sunlight, while
lions are consumers.

Ans: D. A is false but R is true.

21. Identify the type of each of the following reactions stating the reason for your
answers.
A. Fe2O3 + 2Al → Al2O3 + 2Fe + heat
B. Pb (NO3)2 + 2KI → PbI2( )+ 2KNO3

Ans: A. Exothermic Displacement reaction/Redox reaction.
Heat is evolved or a More reactive element displaces a less reactive
element or aluminium reduces iron (II) oxide to iron
B. Double displacement / Precipitation reaction
As there is an exchange of ions between reactants and products
(Yellow) precipitate (of Lead iodide) is formed

23. Attempt either option A or B.
A. List the steps for the synthesis of glucose by the plants. What special
feature is found in desert plants related to this process?
OR
B. Explain the role of the following enzymes in the process of digestion of food
in humans:
(i) Salivary amylase
(ii) Pepsin
(iii) Trypsin
(iv) Lipase

Ans: A. Steps of synthesis of glucose in plants:
* Absorption of light energy by chlorophyll
* Conversion of light energy to chemical energy and splitting of water
molecules into hydrogen and oxygen
* Reduction of carbon dioxide into carbohydrates.
* Desert plants take up carbon dioxide at night and prepare an
intermediate which is acted upon by the energy absorbed by the
chlorophyll during the day
OR
B.
* Salivary amylase – breaks down starch which is a complex molecule
to sugar.
* Pepsin – Helps to digest proteins in stomach.
* Trypsin – It helps in digesting proteins to amino acids.
* Lipase – Breaking down of emulsified fats to fatty acids and glycerol

27. Give reasons for the following
i. Certain metals are used for making cooking utensils.
ii. Hydrogen gas does not evolve when certain metals except Mg & Mn
react with nitric acid.

ANS: A. Certain metals (like aluminium/ copper) are used for making cooking
utensils as they are good conductors of heat and have high melting
points.
B. Hydrogen gas is not evolved when a metal reacts with nitric acid. This is
because HNO3 is a strong oxidising agent. It oxidises the H2 produced to
water and itself gets reduced to any of the nitrogen oxides (N2O, NO,
NO2). But magnesium (Mg) and manganese (Mn) react with very dilute
HNO3 to evolve H2 gas.

29.Water is used by the leaves of the plants for photosynthesis but rather than
watering the leaves, we water the plant through the soil. How does this water
reach the leaves of the plant?

Ans: ● In plants, the water is absorbed by the plants from the soil through the
roots. Xylem tissue of the roots, stems and leaves are interconnected to
form a continuous system of water conducting channels. (1)
● During the day, when stomata are open, the transpiration pull becomes
the major driving force for the movement of water in the xylem. (1)
● Evaporation of water molecules from the stomata creates a suction which
pulls water from the xylem cells of roots to the stem and then to the
leaves.

30. A. In a family of four individuals, the father possessed long ears and the mother
possessed short ears. If the parents had pure dominant and recessive traits
respectively and F1 individual is married to an unrelated individual of the
same genotype, then calculate the ratio of genetic makeup of F2 generation.
Show a suitable cross.
B. If father had short ears and the mother had long ears, and both the parents
are homozygous for the allelic pair of genes, explain what effect it will have
on the ratio of genetic makeup in F2 generation, if F1 individual is married
to an unrelated individual of the same genotype.

Ans: (Any letter which clearly indicated dominant and recessive ears, example, L or
E or any other)
A. LL × ll
F1= Ll
Ll X Ll
1LL:2Ll:1ll. (2)

B. No change in ratio/the ratio of F2 generation will still be 1LL:2Ll:1ll/ ratio
will be the same.
As the cross is still between a pure dominant and recessive allele/ genes/
traits/characters /as shown in the cross above.
Question No. 34 to 36 are long answer questions.
34 Attempt either option A or B.
A.
(i) “Keerthi thinks that Substitution reaction occurs in saturated
Hydrocarbons, on the contrary Krishi thinks, it occurs in unsaturated
Hydrocarbons.” Justify with valid reasoning whose thinking is correct.
(ii) “Methane and Propane and their Isomers are used as fuels” Comment.
Draw the electron dot structure of the immediate lower homologue of
Propane. Give any two characteristics of homologues of a given
homologous series.
(iii) A mixture of oxygen and ethyne is burnt for welding. Can you predict
why a mixture of ethyne and air is not used?
OR
B.
(i) ‘A’ & ‘B’ are sodium salts of long-chain carboxylic acid and long chain
Sulphonic acid respectively. Which one of A or B will you prefer as a
cleansing agent while using underground water (hand pump water)?
Give the reason for your answer.
(ii) Elaborate on the process of cleansing action. Illustrate micelle with the
help of labelled diagram.
(iii) Write the chemical equation of the preparation of soap from an ester
CH3COOCH3. What is the name of this process?

Ans: A.
(i) Keerthi’s thinking is correct as substitution reactions occur in saturated
hydrocarbons, hydrogen atoms are replaced with heteroatoms in
saturated hydrocarbons. Whereas in unsaturated hydrocarbons an
addition reaction occurs, simple molecules are added across double
and/or triple bonds.
(ii) Methane and propane undergo combustion reaction in presence of
oxygen and produce large amount of energy.
The lower homologue of propane is ethane has the following electron
dot structure:

ANY TWO CHARACTERISTICS – Difference in -CH2- / 14u molecular mass of any two adjacent
homologues. – Same general formula/ functional group – Similar chemical properties – Gradual change in physical properties
(iii) The mixture of ethyne and oxygen in sufficient amounts undergoes
complete combustion to fire a clean blue flame. In pressure of
insufficient supply of oxygen or in presence of air, ethyne does not
undergo complete combustion and produces sooty flame.
OR
B.
(i) ‘B’ is preferred for cleansing action. The calcium and magnesium salts
present in underground water are precipitated with carboxylic acids.
The Ca++ and Mg++ salts of sulphonic acid are soluble in water. ‘B’ is a
more effective cleansing agent in presence of Ca and Mg salts.
(ii)
* Soaps are molecules in which the two ends have differing
properties, one is hydrophilic, that is, it dissolves in water, while the
other end is hydrophobic, that is, it dissolves in hydrocarbons.
* The molecules of soap are sodium or potassium salts of long-chain
carboxylic acids. The ionic end of soap dissolves in water while the
carbon chain dissolves in oil. The soap molecules, thus form
structures called micelles where one end of the molecules is
towards the oil droplet while the ionic end faces outside. This forms
an emulsion in water. The soap micelle thus helps in dissolving the
dirt in water and we can wash our clothes clean.

35. The image below shows a developing fetus in the mother’s womb. The
developing fetus is connected to the placenta by means of umbilical cord.
The Umbilical vein and artery run inside the umbilical cord.

CBSE Class 10 Science Sample Paper 2023-24 2

(i) Name two substance that moves through the blood vessels. (1)
(ii) If the placenta has less villi how will it affect the baby’s growth? (1)
(iii) Name the region where the embryo develops inside the female body.
Explain how this region is adapted for nourishing the baby. (1)
(iv) Some of the fetal cells fall off into the amniotic fluid and can be
collected by careful procedure. The cells were screened and found to
contain XY chromosome. (2)

a) What is the sex of the foetus?
b) How is this prenatal sex determination misused?
For visually impaired students
B. A developing fetus is connected to the placenta by means of umbilical cord.
The Umbilical vein and artery run inside the umbilical cord.
(i) Name two substance that moves through the blood vessels.
(ii) If the placenta has less villi how will it affect the baby’s growth?

(iii) Name the region where the embryo develops inside the female body.
Explain how this region is adapted for nourishing the baby. (1)
(iv) Some of the fetal cells fall off into the amniotic fluid and can be
collected by careful procedure. The cells were screened and found to
contain XY chromosome.
a) What is the sex of the foetus?
b) How is this prenatal sex determination misused?

Ans:

(i) Vegetative propagation/ asexual reproduction.
(ii) More crops in same time interval, genetically identical, flower fruit
faster, no need to depend on pollinators.
(iii) Cross pollination, the pollen from anther will be transferred the stigma
of another banana plant using agents like wind, water, or insects etc.
(iv) There would be minor changes/some variation during the process of
copying of the DNA.
OR
B.
(i) Nutrients/glucose/oxygen/waste. (any two) (1)
(ii) less surface area for nutrients (glucose/oxygen) to pass from mother to
embryo slow growth. (1)
(iii) uterus; has thick lining with rich supply of blood to nourish the embryo.
(iv)
a) male child
b) misused as if the foetus is female, some people engage in aborting
the child leading to female foeticide.
For visually impaired students
A.
(i) Nutrients/glucose/oxygen/waste. (any two)
(ii) less surface area for nutrients (glucose/oxygen) to pass from mother to
embryo slow growth.
(iii) uterus; has thick lining with rich supply of blood to nourish the
embryo.
(iv)
a) male child
b) misused as if the foetus is female, some people engage in aborting
the child leading to female foeticide.

37.A. Distinguish between ethanol and ethanoic acid experimentally.
Attempt either subpart B or C.
B. Give the IUPAC name of the first member of Alkene which is formed by
addition of conc. sulphuric acid to it. Illustrate the change with the help
of a chemical equation.
OR
C. “All combustion reactions are oxidation but all oxidation reactions are
not combustion.” Justify.

Ans: A. A – Sodium chloride
Y – Chlorine gas,
Z – Hydrogen gas,
M – Sodium metal,
P – Sodium ethanoate &
R – Ethyl ethanoate/ester
Student to attempt either subpart B or C.
B. Any activity similar to the given figure

OR
C. Chlor alkali process
The process is called the chlor-alkali process because of the products
formed from chlorine and alkali for sodium hydroxide.

38. Mohan and Rohit observed that shoots of a plant growing in shade bend
towards the sunlight. Whereas, leaves of ‘Touch me not’ plant fold and droop
soon after touching. They were curious to know how these movements occur in plantsIn order to help them understand the movements in the plants, answer the
following questions:
Attempt either subpart A or B.
A. What causes the bending of shoots in the plants as shown in figure A?
OR
B. What causes the folding of the leaves in ‘Touch me not’ plant as shown
in figure B? (2)
C. Compare the movement of growth of the pollen tube towards ovule with
the movements shown in part A of the above figure. (1)
D. Compare the movement shown in figure B with the movement of body
parts in the animals. (1)

39. During a field trip, Mohan and Rohit observed that shoots of sunflower plants
bend towards the sunlight. Whereas, leaves of ‘Touch me not’ plant begin to
fold and droop soon after touching even during the day. They were curious to
know how these movements occur in plants.
Attempt either subpart A or B.
A. What causes the bending of shoots in the sunflower plants towards
sunlight?
OR
B. What causes the folding of the leaves in ‘Touch me not’ plants when
touched by hand? (2)
C. Compare the movement of growth of the pollen tube towards ovule with
the bending of shoots of sunflower plant towards sunlight. (1)
D. Compare the movement in folding of leaves of ‘Touch me not’ plants with
the movement of body parts in the animals. (1)

Ans: A.
● Bending of shoots of plants is a response to the stimulus and a
directional, growth-related movement.
● When growing plants detect sunlight, a hormone called auxin,
synthesized at shoot tip helps the cells to grow longer.
● When light is coming from one side of the plant, auxin diffuses to the
shady side of the shoot.
● This concentration of auxin stimulates the cells of the shoot to grow
longer on the side of the shoot which is away from the light. Thus, plant
appears to bend towards light.
OR
B.
● Leaves of ‘Touch me not’ plant respond to the stimulus by showing
growth independent movement.
● These plants use electrical–chemical means to convey the information
from cell to cell.
● Movement happens at a point different from the point of touch.
● Plant cells change shape by changing the amount of water in them,
resulting in swelling or shrinking, and therefore in changing shape.
C. Growth of pollen tubes towards the ovule is an example of
chemotropism whereas bending of shoots towards sunlight is an
example of phototropism. (1)
D.
i) Although both plants and animals show electrical–chemical means to
convey the information from cell to cell but unlike nerve cells in
animals there is no specialized tissue in plants for conduction of
information. (0.5)
ii) In animal cells, change in shape occurs because of the specialized
proteins found in muscle cells; plant cells change shape by changing
the amount of water in them. (0.5)

39. Azim Taraporewala was a traveller and science enthusiast. During one of his
travels he found himself on the edge of an island without any mode of
communication. As he had read in many stories, he thought he would light a
fire on the beach and travelling boats or ships could see that fire and come to
give him a ride. He had run out of lighters and match-sticks but had a reading
glass. Being a science enthusiast he knew some tricks and used that lens and
a scrap of paper to light a fire, with the help of scorching rays from the sun.
A. Which lens can be used by Azim to create the fire?
B. What property of the lens helps Azim to create the fire?
Attempt either subpart C or D.
C. List two more uses of this kind of lens.
OR
D. Explain with reason the condition under which the lens can form both
real as well as virtual images.

Ans: A. Convex lens.
B. Converging property. The lens can converge parallel rays to one point.
Student to attempt either subpart C or D
C. To correct hypermetropia, lenses of telescopes, microscopes and slide
projectors.
OR
D. If the object is kept between the optical centre and the focus the image
obtained is virtual, rest in all cases the image is real.

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