Last year question paper class 10 CBSE science

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CBSE Previous Year Question Paper For Class 10 Science 2020

(I) Please check that this question paper contains 23 printed pages.

(II) Code number given on the right hand side of the question paper should be written on the title pages of the answer - book by the candidate.

(III) Please check that this question paper contains 30 questions.

(IV) Please write down the Serial Number of the question in the answer - book before attempting it.

(V) 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m., the students will read the question paper only and will not write any answer on the answer - book during this period.

Question Paper 2020 |Previous year's Questions Paper

ENGLISH
SECTION A

1. Which oils should be chosen for cooking to remain healthy ? 1

2. Define the term induced electric current. 1

3. Answer question numbers 3(a) - 3(d) onthe basis of your understanding of the following paragraph and the related studied concepts :

Around the year 1800, only 30 elements were known. Dobereiner in 1817 and Newlands in 1866 tried to arrange the then known elements and framed laws which were rejected by the scientists. Even after the rejection of the proposed laws, many scientists continued to search for a pattern that correlated the properties of elements with their atomic masses.

The main credit for classifying elements goes to Mendeleev for his most contribution to the early development of a Periodic table of elements wherein he arranged the elements on the basis of their fundamental property, the atomic mass and also on the similarity of chemical properties. The formulae of their hydrides and oxides were treated as basic criteria for the classification of the elements.

However, Mendeleev's classification also had some limitations as it could not assign the position to isotopes. He also left some gaps in the periodic table.

3. (a) State Mendeleev's Periodic Law. 1

3. (b) Why did Mendeleev leave some gaps in the Periodic table ? 1

3. (c) If the letter 'R' was used to represent any of the elements in the group, then the hydric and oxide of carbon would respectively be represented as 1

(i) RH⁴’ RO

(ii) RH⁴' RO²

(iii) RH²' RO²

(iv) RH²’ RO

3. (d) Isotopes are 1

(i) Atoms of an element with similar chemical properties but different atomic masses.

(ii) Atoms of different elements with similar chemical properties but different atomic masses.

(iii) Atoms of an element with different chemical properties but same atomic masses.

(iv) Atoms of different elements with different chemical properties but same atomic masses.

4. Answer question numbers 4(a) - 4(d) on the basis of your understanding of the following paragraph and the related studied concepts :

India today is facing the problem of overuse of resources, contamination of water and soil and lack of methods of processing the waste. The time has come for the world to say goodbye to "single - use plastics". Steps must be undertaken to develop environment - friendly substitutes, effective plastic waste collection and methods of its disposal.

Indore treated 15 lakh metric tonnes of waste in just 3 years, through biomining and bioremediation techniques. Bioremediation involves introducing microbes into a landfill to naturally 'break' it down and biomining involves using trommel machines to sift through the waste to separate the 'soil' and the waste component. The city managed to chip away 15 lakh metric tonnes of waste at a cost of around ₹10 crore. A similar experiment was successfully carried out in Ahmedabad also.

4. (a) State two methods of effective plastic waste collection in your school. 1

4. (b) Name any two uses of "single - use plastic" in daily life. 1

4. (c) If we discontinue the use of the plastic, how can an environment - friendly substitute be provided ? 1

4. (d) Do you think microbes will work similarly in landfill sites as they work in the laboratory ? Justify your answer. 1

5. Fertilisation is the process of 1

(A) transfer of male gamete to female gamate.

(B) fusion of nuclei of male and female gamate.

(C) adhesion of male and female reproductive organs.

(D) the formation of gametes by a reproductive organ.

6. 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 1

(A) Urethra

(B) Nephron

(C) Ureter

(D) Urinary bladder

OR

Pseudopodia are 1

(A) small hair - like structures present on unicellular organisms.

(B) false 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.

7. Which one of the following statements is correct about the human circulatory system ? 1

(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.

8. Which one of the following statements is not true about nuclear energy generation in a nuclear reactor ? 1

(A) Energy is obtained by a process called nuclear fission.

(B) The nucleus of Uranium is bombarded with high energy neutrons.

(C) A Chain reaction is set in the process.

(D) In this process a tremendous amount of energy is released at a controlled rate.

The biggest source of energy on Earth's surface is 1

(A) Biomass

(B) Solar radiations

(C) Tides

(D) Winds

9. If a person has five resistors each of value 1/5 Π, then the maximum resistance he can obtain by connecting them is 1

(A) 1 π

(B) 5 π

(C) 10 π

(D) 25 π

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 becom 1

(A) two times.

(B) half.

(C) one - fourth.

(D) four times.

10. Fleming's Right- hand rule gives 1

(A) magnitude of the induced current.

(B) magnitude of the magnetic field.

(C) direction of the induced current.

(D) both, direction and magnitude of the induced current.

11. How much of the net primary productivity of a terrestrial ecosystem is eaten ans digested by herbivores ? 1

(A) 100%

(B) 10%

(C) 1%

(D) 0.1%

12. Choose the incorrect statement from the following: 1

(A) Ozone is a molecule formed by three atoms of oxygen.

(B) Ozone shields the surface of the Earth from ultraviolet radiations.

(C) Ozone is deadly poisonous.

(D) Ozone gets decomposed by UV radiations.
For questions numbers 13 and 14, two statements are given - one labelled as Assertion (A) and the other labelled as 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 (A).

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

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

(d) (A) is false, but (R) is true.

13. Assertion (A): The reaction
MnO2 + 4HC1 -> MnC1² + 2H²O +C1²
is an example of a redox reaction.
Reason (R): In this reaction, HC1 is reduced to C1² whereas MnO2 is oxidised to MnC1². 1

14. Assertion (A) : 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 same function in different species are called analogous organs. 1

SECTION B

15. When hydrogen sulphide gas is passed through a blue solution of cooper sulphate, the colour of the solution fades and a black precipitate is obtained.

(a) Name the type of reaction mentioned above.

(b) Why does the colour of the solution fade away ?

(c) Write the chemical name of the black precipitate formed.

(d) Give the balanced chemical equation for the reaction involved. 3

Study the figure below and answer the following questions:

(a) Name the process depicted in the diagram.

(b) Write the composition of the anode and the cathode.

(c) Write the balanced chemical equation of the reaction taking place in this case.

(d) The reaction does not take place if a few drops of dilute sulphuric acid are not added to water. Why ? 3

16. A concave mirror is used for image formation for different positions of an object. What inferences can be drawn about the following when an object is placed at a distance of 10 cm from the pole of a concave mirror of local length 15 cm ?

(a) Position of the image

(b) Size of the image

(c) Nature of the image
Draw a labelled ray diagram to justify your inferences. 3

17. Define the term evolution. "Evolution cannot be equated with progress". Justify this statement. 3

"During the course of evolution, organs or features may be adapted for new functions". Explain this fact by choosing an appropriate example. 3

18. Write in tabular form the location and function of the hormones secreted by each of the following glands present in the human body:

(a) Pituitary gland

(b) Thyroid gland

(c) Pancreas 3

19. List three differentiating features between the processes of galvanisation and alloying. 3

OR

Compare in tabular form the reactivities of the following metals with cold and hot water :

(a) Sodium

(b) Calcium

(c) Magnesium

20. Carbon, a member of group 14, forms a large number of carbon compounds estimated to be about three million. Why is this property not exhibited by other elements of this group ? Explain. 3

21. Define geotropism. Draw a labelled diagram of a plant showing geotropic movements of its parts. 3

22. (a) For the same angel of incidence of 45°, the refraction angel in two transparent media P and Q is 20° and 30° respectively. Which of the two is optically denser and why ?

(b) Define 1 dioptre power of a lens.

(c) Find the focal length of a lens of power + 0.5 D. 3

23. How will you use two identical glass prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light ? Draw and label the ray diagram. 3

24. A person may suffer from both myopia and hypermetropia defects.

(a) What is this condition called ?

(b) When does it happen ?

(c) Name the type of lens often required by the person suffering from this defect. Draw labelled diagram of such lenses. 3

SECTION C

25. Define an alloy. How is an alloy prepared ? List two advantages of making alloys. Write the composition of stainless steel. Why is steel preferred over iron ? List two reasons. 5

26. Draw a neat diagram showing fertilisation in a flower and label (a) Pollen tube, (b) Male germ cell and (c) Female germ cell, on it. Explain the process of fertilisation in a flower. What happens to the (i) ovary and (ii) ovule after fertilisation ? 5

(a) What is puberty ?

(b) Describe in brief the functions of the following parts in the human male reproductive system :
(i) Testes

(ii) Seminal vesicle

(iii) Vas deferens

(iv) Urethra

(c) Why are testes located outside the abdominal cavity ?

(d) State how sperms move towards the female germ cell.

27. Draw a schematic of a circuit consisting of a battery of 3 cells of 2 V each, a combination of three resistors of 10_Π_ , 20_Π_ and 30 _Π_ connected in parallel, a plug key and an ammeter, all connected in series. Use this circuit to find the value of the following :

(a) Current through each resistor

(b) Total current in the circuit

(c) Total effective resistance of the circuit 5

Two identical resistors, each of resistance 15 _Π_ , are connected in (i) series, and (ii) parallel, in turn to a battery of 6 V. Calculate the ratio of the power consumed in the combination of resistors in each case. 5

28. A cloth strip dipped in onion juice is used for testing a liquid 'X'. The liquid 'X' changes its odour. Which type of an indicator is onion juice ? The liquid 'X' turns blue litmus red. List the observations the liquid 'X' will show on reacting with the following :

(a) Zinc granules

(b) Solid sodium carbonate

Write the chemical equations for the reactions involved. 5

Define water of crystallisation. Give the chemical formula for two compounds as examples. How can it be proved that the water of crystallisation makes a difference in the state and colour of the compounds ? 5

29. (a) Why is nutrition necessary for the human body ?

(b) What causes movement of food inside the alimentary canal ?

(c) Why is small intestine in herbivores longer than in carnivores ?

(d) What will happen if mucus is not secreted by the gastric glands ? 5

30. (a) State with reasons the mode of connecting all electrical appliances in common domestic electrical circuits.

(b) Which two separate circuits are often used in domestic electric circuits and why ?

(c) When does an electrical short circuit occur ? How can it be prevented ?