Science Unsolved Sample Paper Solutions CBSE Class 10

Section - A

Select and write one most appropriate option out of the four options given for each of the questions 1 – 20

  • 1.(a) ∠i, ∠A, ∠D
  • Explanation: It is clear from the ray diagram that ∠A, ∠i and ∠D are correctly marked. ∠A represents the angle of prism which is correctly marked. ∠D represents the angle of deviation which is formed between the emergent ray and incident ray is correctly marked. ∠i is the angle formed by the incident ray with the normal is correctly marked.
  • 2.(c) both (a) and (b)
  • Explanation: Burning of the candle is both physical and chemical change. Burning of the candle melts the wax and hence physical state of wax changes from solid to liquid. Again the wax combines with the atmospheric oxygen and changes to carbon dioxide, heat and light. Thus it is both a physical and the chemical change.
  • 3.(d) Ptyalin
  • Explanation: The pancreas secretes pancreatic juice, which contains various enzymes like trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, pancreatic lipase, and amylase. Pancreatic juice does not include Ptyalin. It is produced by the gastric glands in the stomach.
  • 4.(a) 2 Ω
  • Explanation: Let l be the length and A be the area of cross section.
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Hence, the aerial’s new resistance is 2 Ω.

5. (b) under secretion of thyroxine.

Explanation: The excess secretion of thyroxine hormone in babies causes cretinism. Slow heartbeat, low blood pressure, low body temperature, stunted growth, and mental retardation, awkward body with a pot belly, protruding tongue, pigeon breast, and retarded sexual development are all symptoms of this condition.

6. (c) TtWW

Explanation: The genetic makeup of tall parent could be TtWW. Since half of the progenies are short, the parent plant will have a set of recessive genes as well; all progenies produced violet flowers, indicating that violet is the dominant colour over white.

7. (d) nature of the material

Explanation: The resistivity of a material is constant at a constant temperature. Resistivity of  material does not depend on length, thickness and shape of the material. It only depends on the temperature.

8. (c) Testosterone from testes and estrogen from ovary.

Explanation: The release of oestrogen and testosterone is associated to puberty changes. In females, oestrogen is secreted from the ovary, while testosterone is secreted from the testes in males.

9. (c) Stomach and pancreas

Explanation: Pepsin enzyme is secreted by the stomach that breaks down proteins into smaller amino acids. Trypsin enzyme is secreted by the pancreas that breaks down proteins.

10. (b) ₹ 24

Explanation: Consumption of electrical energy in 3 hours can be calculated by using the formula:

E = P × t

= 2 kW × 3 hour = 6 kWh

Unit cost of electrical energy

=  ₹ 4 per kWh

Therefore, the cost of energy used for three hours will be: 4 × 6 =  ₹ 24

11. (c) Secreted by liver and stored in gall bladder

Explanation: Bile juice is secreted by the liver and stored in gall bladder. It helps in the breakdown of fats into fatty acids.

12. (a) smelling

Explanation: The olfactory neurons have olfactory receptors on their surfaces. Their primary function is to detect odours.

13. (c) Galvanometer

Explanation: Galvanometer is an instrument that is used to detect the presence of the current in the circuit. And when magnet is moved near the coil, the current is induced in the coil.

14. (b) Mid brain

Explanation: The hypothalamus is a tiny structure of the brain. It is located near the pituitary gland at the base of the brain. The hypothalamus plays a significant part in a variety of tasks, including hormones released, controlling one’s body temperature.

15. (c) Antacid

Explanation: Antacids such as sodium bicarbonate and magnesium hydroxide etc are used in treating indigestion. They are basic in nature and reacts with excess acid present in the stomach and neutralises it.

16. (c) Same at all points

Explanation: The magnetic field inside a solenoid is proportional to both the applied current and the number of turns per unit length. There is no dependence on the diameter of the solenoid, and the field strength does not depend on the position inside the solenoid, i.e., the field inside is constant.

The magnetic field is nearly uniform field in the center, i.e., inside of a long solenoid and the field outside is weak and divergent.

17. (a) Both A and R are true and R is not the correct explanation of A

Explanation: Due to high electrical conductivity of copper, it conducts the current without offering much resistance. The copper being diamagnetic material does not get magnetised due to current through it and hence does not disturb the current in the circuit. Thus, both assertion and reason are correct and reason is the correct explanation of the assertion.

18. (c) A is true but R is false

Explanation: Hydrogen gas is not evolved when a metal reacts with nitric acid. It 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). Thus, assertion is true but reason is false.

19. (b) Both A and R are true and R is not the correct explanation of A

Explanation: Both the statements are true, but full form of ABA has no relation with the function of cytokinin. Thus, both assertion and reason are correct but reason is not the correct explanation of the assertion.

20. (a) Both A and R are true and R is the correct explanation of A

Explanation: A ray of light that travels obliquely from one transparent medium to another will change its direction in the second medium. It is nothing but the process called refraction. This occurs due to change in the speed of light as it enters from one transparent medium to another. Thus, both assertion and reason are correct and reason is the correct explanation of the assertion.

Section - B

Q. no. 21 to 26 are very short answer questions.

  • 21. (i) Ethene
  • (ii) Pentane
  • (iii) 2-Bromopropane
  • (iv) 4-chloro-2-pentene

22. A chemical equation should be balanced because it follows the law of conservation of mass. This law states that during a chemical change, matter is neither created nor destroyed but only changes from one form to another. So, while showing a chemical change in the form of a chemical equation we need to balance the number of atoms of each element on both sides of the equation.

  • (i) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O
  • (ii) NaCl + AgNO3 → AgCl + NaNO3
  • 23. (i) Involuntary action
  • (ii) Involuntary action
  • (iii) Voluntary action
  • (iv) Involuntary action
  • OR
  • (i) Tongue is the gustatory receptor present in the human body. Nasal cavity is the olfactory receptor present in the human body.
  • (ii) Dendrite → Cell body → Axon → End point of Neuron.
  • 24. (i) Yes, he is correct colour at position 5 is blue which correspond to colour of copper sulphate solution. Position 7 is violet colour which corresponds to the colour of brinjal.
  • (ii) When two identical prisms are placed in such a way that one is placed inverted with respect to the other and a narrow beam of light when incident on one prism, it emerges out of the second prism as white light.
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25. (i) Biodegradable wastes can be easily degraded by natural organisms like bacteria and fungi but non-biodegradable wastes cannot be degraded in a natural way by the action of microbes, they stay in environment as such. There are various techniques like recycling to degrade these nonbiodegradable substances. Biodegradable wastes can be used as a compost or manure. Hence both biodegradable and non-biodegradable wastes should be discarded in two separate dustbins.

(ii) The food chain will be Wheat grains → Rat → Snake → Peacock

Peacock has the maximum concentration of harmful chemicals as it is placed at the top level of this food chain and due to biomagnification, the harmful chemicals concentration is maximum in the body of organisms placed at the top of a food chain.

26. (i) The sphygmomanometer is a device that is composed of an inflatable cuff, a measuring unit, and a valve. It is a device that is used for measuring blood pressure.

(ii) The blood exerts a certain amount of pressure on these blood vessels. This exerted pressure on the wall of arteries is termed as blood pressure. The normal blood pressure of a person is 120/80 mm Hg.

OR

Hydrochloric acid which is secreted in our stomach has following functions:

1. It makes the medium acidic so that the enzyme pepsin gets activated and acts upon proteins to convert them into peptones and proteases.

2. It also kills the bacteria that might have entered to our body along with the food we eat.

Section - C

Q. no. 27 to 33 are short answer questions.

27. Aluminium oxide is said to be an amphoteric oxide because it reacts with both acids and bases to produce salt and water. Generally, metal oxides are basic in nature. Some metallic oxides like aluminium oxide show both acidic as well as basic behaviour. Other oxides which show amphoteric behaviour are zinc
oxide (ZnO), lead oxide (PbO) and stannous oxide (SnO).

Al2O3 + 6HCl → 2AlCl3 + 3H2O
Al2O3 + 2NaOH → 2NaAlO2 + H2O

OR

(i) Potassium metal reacts violently with water forming potassium hydroxide and hydrogen gas. As the reaction is highly exothermic, it causes the evolved hydrogen gas to burn and catch fire immediately.

2K + 2H2O → 2KOH + H2↓ + Heat

But calcium when reacts with cold water produces very less heat which is not sufficient to burn hydrogen gas formed.

Ca + 2H2O → Ca(OH)2 + H2

(ii) X is non-metal as non-metallic oxides are acidic in nature so they turn blue litmus red.

(iii) Compound Z is ionic in nature as metal X combines with non-metal Y by transfer of electrons to form ionic compound. As it is an ionic compound it will not dissolve in petrol or kerosene because they are organic solvents.

28. The problems caused by the non-biodegradable wastes are:

1. As non-biodegrdable substances cannot be degraded naturally so they accumulate in the soil causing pollution and also reduces the fertility of the soil.

2. Some pesticides like DDT, mercury etc., which are non-biodegradable undergo biological magnification by entering into food chain.

3. If these substances do not undergo proper disposal techniques they will accumulate in soil thus will reduces the fertility of soil.

4. Some harmful non-biodegradable substances may cause diseases in living organisms.

29. Take a battery (12 V), a variable resistance (or a rheostat), an ammeter (0–5 A), a plug key, and a long
straight thick copper wire. Insert the thick wire through the centre, normal to the plane of a rectangular cardboard. Take care that the
cardboard is fixed and does not slide up or down. Connect the copper wire vertically between the points X and Y, as shown in diagram in series with the battery, a plug and key. Sprinkle some iron filings uniformly on the cardboard. Keep the variable of the rheostat at a fixed position and note the current through the ammeter. Close the key so that a current flows through the wire.
Ensure that the copper wire placed between the points X and Y remains vertically straight. Gently tap the cardboard a few times. Observe the pattern of the iron filings. It is observed that the iron filings align themselves showing a pattern of concentric circles around the copper wire. These represent the magnetic field lines.

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  • (i) Right Hand Thumb Rule.
  • (ii) (a) Yes, alpha particles being, positively charged constitutes a current in the direction of motion.
  • (b) No, neutron being electrically neutral constitute no current.

30. (i) (a) If we use only baking soda it imparts bitter taste to the cake because baking soda which is sodium hydrogen carbonate when heated produces sodium carbonate that gives bitter taste to the cake.

2NaHCO3 → Na2CO3 + CO2 + H2O

(b) By adding tartaric acid to baking soda, we can convert into baking powder.

(ii) The process of electrolysis of concentrated solution of sodium chloride is called chlor-alkali process. It is named so because of the products formed chlor for chlorine and alkali for sodium hydroxide.

(iii) (a) PbCO3 + 2HNO3 → Pb(NO3)2 + H2O + CO2
Pb(NO3)2 + 2HCl → PbCl2 + 2HNO3
(b) Zn + H2SO4 → ZnSO4 + H2
ZnSO4 + Na2CO3 → ZnCO3 + Na2SO4
  • 31. (i) Metal that exists in liquid state at room temperature is Mercury.
  • (ii) Metal that can be easily cut with a knife are Sodium and Potassium.
  • (iii) Metal that is the best conductor of heat are Silver and gold.
  • (iv) Metals that are poor conductor of heat are Mercury and lead.

32. (i) Difference between binary fission and multiple fission are :

Binary Fission Multiple fission
1. A single parent cell divides into two daughter cells. It results in production of many daughter cells.
2. Nucleus divides once and then each nucleus gets surrounded by cytoplasm to form two individuals. Nucleus divides repeatedly to form many nuclei and each get surrounded by cytoplasm to form many daughter cells.
3. It occurs under favourable conditions. Example: Binary fission in Amoeba, Paramecium. It occurs under unfavourable conditions. Example: Plasmodium.

(ii) (a) Stigma which is the tip part of carpel and is sticky in nature so it serves as a platform for the landing of pollen grains from anthers during pollination.

(b) Pollen tube which arises from pollen grains passes through style and reaches ovary. Through this the male gamete is transferred towards female gamete present within ovule of ovary for fertilisation.

(c) Female gamete which fuses with male gamete to form zygote. This process is called fertilisation.

OR

(i) This process is called regeneration and example is hydra. When Planaria is cut into three pieces each piece grow into separate individual.

  • (ii) (a) Oviducts/Fallopian tubes
  • (b) Uterus
  • (c) Vagina
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  • 33. (i) Refractive index of a medium with respect to another medium is called relative refractive index.
  • (ii) One dioptre is defined as the power of a lens of focal length 1 metre.
  • (iii) Lateral shift is directly proportional to angle of incidence.

Section - D

Q. no. 34 to 36 are long answer questions.

34. When Mendel crossed pure tall (TT) pea plants with pure dwarf (tt) pea plants, in F1 generation he found that all pea plants were tall (Tt). There were no dwarf plants produced in F1 generation. When he self-pollinated these F1 plants, in F2 generation he obtained tall and dwarf plants in the ratio 3 : 1. Thus as three-fourths of the plant in F2 generation are tall and one-fourth is dwarf so tall is a dominant trait whereas dwarf is a recessive trait (which expressed itself only in homozygous condition). So, he concluded that for a particular trait (here in this example height of the plant) it may be dominant or recessive.
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When Mendel crossed pure pea plants with round, yellow seeds with pure plants with wrinkled, green seeds, in F1 generation all pea plants with round and yellow seeds were produced. This shows that round and yellow are dominant characters whereas green and wrinkled are recessive characters. Again when these F1 plants were crossed round, yellow pea plants as well as green, wrinkled seeds pea plants were produced. But in addition to these two new characters were produced i.e., round and green, wrinkled and yellow seeds pea plants were produced.
This shows that two pair of characters combine in F1 generation but they get separated and behave independently in F2 generation.

Round-yellow, round-green, wrinkled-yellow, wrinkled-green—9 : 3 : 3 : 1.

  • 35. (a) (i) 1. Diamond
  • 2. Graphite
  • 3. Buckminsterfullerene
  • (ii) Catenation property
  • (iii) Graphite.
  • (iv) Diamond is the hardest substance while graphite is smooth and slippery and also graphite is good conductor of electricity.
  • (b) (i) Clear flame
  • (ii) Sooty flame
  • (iii) Sooty flame
  • (iv) Clear flame

36. We have, u = – 25 cm, f = – 15 cm, h = + 4 cm

Using mirror equation, we get

or    v = – 37.5 cm

Hence, for a sharp image the screen should be placed in front of the mirror at a distance of 37.5 cm. It is a real image.

So image height, h’ = 6 cm, image is inverted and enlarged.

OR

A concave mirror converge the sun rays at its focus, f = –10 cm

Object distance, u = –15 cm

Height of object, h1 = 2 cm

Image distance, v = ?

Image height, h2 = ?

Image will be formed at 30 cm distance to the left side of the mirror.

Image formed is real and inverted.

So, image height is 4 cm. Negative sign indicates image is real, inverted.

Section - E

Q.no. 37 to 39 are case - based/data -based questions with 2 to 3 short sub - parts. Internal choice is provided in one of these sub-parts.

37. (a) In the test tube A, the nails are exposed to both air and water. In the test tube B, the nails are exposed to only water, and the nails in test tube C are exposed to dry air. Thus iron nails rust in test tube A, but they do not rust in test tubes B and C.

(b) The necessary conditions for corrosion are air and moisture.

OR

(b) The corrosion can be prevented by painting, oiling, greasing, galvanizing, chrome plating, anodizing or making alloys.

An alloy is a homogeneous mixture of two or more metals, or a metal and a non- metal. It is prepared by first melting the primary metal, and then, dissolving the other elements in it in definite proportions. It is then cooled to room temperature. Example: Stainless steel is an alloy of iron, chromium and nickel.

38. (a) Stamen is the male reproductive part and it produces pollen grains that are yellowish in colour.

(b) The swollen bottom part is the ovary, middle elongated part is the style and the terminal part which may be sticky is the stigma. The ovary contains ovules and each ovule has an egg cell.

(c) The seed contains the future plant or embryo which develops into a seedling under appropriate conditions. This process is known as germination.

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(a) Given that, I = 0.8 A; t = 5 min = 300 s.

Q = It

Q = 0.8 × 300 = 240 C

(b) One ampere is constituted by the flow of one coulomb of charge per second.

(c) in an electric circuit the direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.

OR

(c) The SI unit of electric charge is coulomb (C), which is equivalent to the charge contained in nearly 6 × 1018 electrons.

CBSE 36 Sample Question Papers
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All Subjects Combined for Class 10 Exam 2023

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