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CBSE X
Set -3
SCIENCE PAPER 2011

Time allowed: 180 minutes; Maximum Marks: 90

 General Instructions: 1) All questions are compulsory. 2) The question paper consists of 42 questions divided into 4 sections A, B, C and D. Section A comprises questions of 01 mark each, Section B comprises questions of 02 marks each, Section C comprises questions of 03 marks each and Section D comprises questions of 05 marks each. 3) All questions in Section A are to be answered in one word, one sentence or as per the exact requirement of the question. 4) There is no overall choice. However, internal choice has been provided wherever necessary.You have to attempt only one of the alternatives in all such questions. 5) In question on construction, drawing should be near and exactly as per the given measurements. 6) Use of calculators is not permitted.

SECTION A

### Question 1

1. What are the various steps in a food chain called?

### Question 2

2. What is the important function of presence of ozone in earth’s atmosphere?

### Question 3

3. Write the electron dot structure of ethane molecule, C2H6.

### Question 4

4. What makes the earth’s atmosphere a heterogeneous mixture?

### Question 27

27. A student was given two permanent slides, one of binary fission in amoeba and other of budding in yeast. He was asked to identify any one difference in the nucleus of the two. One such difference he identified correctly was

Options:
1. Presence of one nucleus in amoeba, two in yeast cell and one in bud.
2. Presence of two nuclei in centrally constricted amoeba, one in yeast cell and one in its bud.
3. Presence of two distant nuclei in amoeba, one in yeast cell and two in bud.
4. Presence of a single nucleus each in amoeba, yeast cell and its attached bud.

### Question 28

28. Binary fission is observed in which one of the following figures?

Options:
1. A
2. B
3. C
4. D

### Question 29

29. To determine the percentage of water absorbed by raisins, raisins are soaked in water for:

Options:
1. 30 seconds
2. 10 minutes
3. 2 to 3 hours
4. 24 hours

### Question 30

30. Raisins are wiped off gently before final weighing with help of

Options:
1. a filter paper
2. a cotton piece
3. a cloth piece
4. a polythene piece

### Question 31

31. The step(s) necessary for determining the percentage of water absorbed by raisins is/are:

Options:
1. Raisins should be completely immersed in water
2. Raisins should be soaked in water for sufficient time
3. Gently wipe dry the soaked raisins
4. All of the above steps.

### Question 32

32.

Rahim recorded the following sets of observations while tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence.

The correct observation is recorded at serial number:

Options:
1. I
2. II
3. III
4. IV

### Question 33

33.

Four students A, B, C and D traced the paths of incident ray and the emergent ray by fixing pins P and Q for incident ray and pins R and S for emergent ray for a ray of light passing through a glass slab.

The correct emergent ray was traced by the student:

Options:
1. A
2. B
3. C
4. D

### Question 34

34. Mohan obtained a sharp inverted image of a distant tree on the screen placed behind the lens. He then moved the screen and tried to look through the lens in the direction of the object. He would see:

Options:
1. A blurred image on the wall of the laboratory.
2. An erect image of the tree on the lens.
3. No image as the screen has been removed
4. An inverted image of the tree at the focus of the lens.

### Question 35

35. For finding the focal length of a convex lens by obtaining the image of a distant object, one should use as the object.

Options:
1. A well lit distant tree
2. Window grill in the class room
3. Any distant tree
4. A lighted candle kept at the other end of the table.

### Question 36

36. To find the focal length of a concave mirror Rahul focuses a distant object with this mirror. The chosen object should be:

Options:
1. A tree
2. A building
3. A window
4. The sun

### Question 37

37. The colour of an aqueous solution of zinc sulphate as observed in the laboratory is:

Options:
1. Green
2. Yellow
3. Blue
4. Colourless

### Question 38

38. To show that zinc is a more active metal than copper, the correct procedure is to:

Options:
1. Add dilute nitric acid on strips of both the metals.
2. Observe transmission of heat through strips of zinc and copper.
3. Prepare solution of zinc sulphate and hang strip of copper into it.
4. Prepare solution of copper sulphate and hang strip of zinc into it.

### Question 39

39. Acetic acid smells like:

Options:
1. A banana
2. Vinegar
3. An orange
4. A lemon

### Question 40

40. Acetic acid solution turns:

Options:
1. Blue litmus red
2. Red litmus blue
3. Blue litmus colourless
4. Red litmus colourless

### Question 41

41. On adding NaHCO3 to acetic acid, a gas is evolved which turns lime water milky due to the formation of:

Options:
1. Calcium bicarbonate
2. Calcium hydroxide
3. Calcium carbonate
4. Calcium acetate

### Question 42

42. A yeast cell in which budding occurs was seen to have:

Options:
1. one bud cell
2. two bud cell
3. three bud cell
4. a chain of bud cells

SECTION B

### Question 5

5.

List any four characteristics of a good fuel.

### Question 6

6. What are non-renewable resources of energy? Give two examples of such resources.

### Question 7

7.

(i) How do you calculate the possible valency of an element from the electronic configuration of its atoms?

(ii) Calculate the valency of element X whose atomic number is 9.

### Question 8

8. On the basis of electronic configuration, how will you identify the first and the last element of a period?

### Question 9

9. State the two laws of reflection of light.

### Question 10

10. The stars appear higher from horizon than they actually are. Explain why it is so.

### Question 11

11. Explain why the planets do not twinkle but the stars twinkle.

### Question 12

12. Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms.

### Question 13

13. Why is DNA copying an essential part of the process of reproduction?

### Question 25

25. (a) In a tabular form, differentiate between ethanol and ethanoic acid under the following heads:

(i) Physical state

(ii) Taste

(iii) NaHCO3 test

(iv) Ester test

(b) Write a chemical reaction to show the dehydration of ethanol.

### Question 26

26. (a) What is a soap? Why are soaps not suitable for washing clothes when the water is hard?

(b) Explain the action of soap in removing an oily spot from a piece of cloth.

SECTION C

### Question 14

14. Explain the terms:

(i) Speciation

(ii) Natural selection

### Question 15

15. Explain how equal genetic contribution of male and female parents is ensured in the progeny.

### Question 16

16. Out of HCl and CH3COOH, which one is a weak acid and why? Describe an activity to support your answer.

### Question 17

17.

Two elements X and Y belong to group 1 and 2 respectively in the same period of periodic table. Compare them with respect to:

(i) the number of valence electrons in their atoms

(ii) their valencies

(iii) metallic character

(iv) the sizes of their atoms

(v) the formulae of their oxides

(vi) the formulae of their chlorides

### Question 18

18.

Draw the ray diagram and also state the position, the relative size and the nature of image formed by a concave mirror when the object is placed at the centre of curvature of the mirror.

### Question 19

19.

(i) “The refractive index of diamond is 2.42”. What is the meaning of this statement?

(ii) Name a liquid whose mass density is less than that of water but it is optically denser than water.

### Question 20

20. What is hypermetropia? Describe with a ray diagram how this defect of vision can be corrected by using an appropriate lens.

### Question 21

21. (a) List two sexually transmitted diseases in each of the following cases:

(i) Bacterial infections

(ii) Viral infections

(b) How may the spread of such diseases be prevented?

### Question 22

22. Explain Mendel’s law of independent inheritance. Give one example.

SECTION D

### Question 23

23.

(a) If the image formed by a lens is diminished in size and erect, for all positions of the object, what type of lens is it?

(b) Name the point on the lens through which a ray of light passes undeviated.

(c) An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find (i) the position (ii) the magnification and (iii) the nature of the image formed.

OR

(a) One - half of a convex lens is covered with a black paper. Will such a lens produce an image of the complete object? Support your answer with a ray diagram.

(b) An object 5 cm high is held 25 cm away from a converging lens of focal length 10 cm.

(i) Draw the ray diagram and

(ii) Calculate the position and size of the image formed.

(iii) What is the nature of the image?

### Question 24

24. (a) Draw a diagram of the longitudinal section of a flower and label on it sepal, petal, ovary and stigma.

(b) Write the names of male and female reproductive parts of a flower.

OR

(a) What is fragmentation in organisms? Name a multicellular organism which reproduces by this method.

(b) What is regeneration in organism? Describe regeneration in planaria with the help of a suitable diagram.