CBSE Class X Science SA2 Question Paper of 2014 with solutions

Downloadable PDF version of the same to be uploaded soon.

Series - HRS

Code No. - 31/1

SUMMATIVE ASSESSMENT - II

SCIENCE

Time allowed : 3 hours

Maximum Marks : 90

General Instructions:
(i) The question paper comprises of two Sections, A and B. You are to attempt both the sections.
(ii) All questions are compulsory.
(iii) All questions of Section A and all questions of Section B are to be attempted separately.
(iv) Question numbers 1 to 3 in Section A are one-mark questions. These are to be answered in one word or in one sentence.
(v) Question numbers 4 to 7 in Section A are two-marks questions. These are to be answered in about 30 words each.
(vi) Question numbers 8 to 19 in Section A are three-marks questions. These are to be answered in about 50 words each.
(vii) Question numbers 20 to 24 in Section A are five-marks questions. These are to be answered in about 70 words each.
(viii) Question numbers 25 to 42 in Section B are multiple choice questions based on practical skills. Each question is a one-mark question. You are to select one most appropriate response out of the four provided to you.

SECTION A

1. List any two properties of the elements belonging to the first group of the modern periodic table.
Ans: (i) They are monovalent.
(ii) They are metals.

2. What is a gene ?
Ans: A gene is a unit of DNA on a chromosome which governs the synthesis of one protein that controls a specific trait of an organism.

3. Give one example each from your daily life where the domestic waste can be effectively reused and recycled.
Ans: (i) Paper envelops can be reversed inside out and reused.
(ii) Waste papers, metals etc. can be collected and sent to the respective industries of recycling.

4. What is the main difference between sperms and eggs of humans ? Write the importance of this difference.
Ans: Sperms are small and motile while eggs are comparatively larger, non-motile and contain food. This difference gives rise to the differences in male and female reproductive organs.

5. List two possible ways in which a concave mirror can produce a magnified image of an object placed in front of it. State the difference, if any, between these two images.
Ans: A concave mirror can produce a magnified image if an object is placed between its pole and focus or between centre of curvature and focus.
The image produced in the first case is virtual and erect while the image produced in the second case is real and inverted.

6. What are decomposers ? List two important roles they play in the environment.
Ans: The organisms which break down the complex organic compounds present in dead organisms into simpler substances are called decomposers.
Two important roles played by them:
(i) They help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment.
(ii) It is only due to the presence of decomposers that the various nutrient elements which were initially taken by plants and animals are returned to the environment.

7. Why is sustainable management of natural resources necessary? Out of the two methods - reuse and recycle - which one would you suggest to practise and why?
Ans: Sustainable management of natural resources is necessary so that the coming generations can also have access to the resources. I would suggest to practise "reuse" because some energy is used to recycle old objects but no energy is required during reuse.

8. What are homologous series of carbon compounds ? Write the molecular formula of two consecutive members of homologous series of aldehydes. State which part of these compounds determines their (i) physical and (ii) chemical properties.
Ans: A group of carbon compounds having similar structures and similar chemical properties in which the successive compounds differ by CH2 group is called homologous series of carbon compounds.
The molecular formula of two consecutive members of homologous series of aldehydes is CH3CHO and C2H5CHO. CH3 and C2H5 determine their physical properties while CHO determines their chemical properties.

9. A carboxylic acid (molecular formula C2H4O2) reacts with an alcohol in the presence of an acid catalyst to form a compound 'X'. The alcohol on oxidation with KMnO4 followed by acidification gives the same carboxylic acid C2H4O2. Write the name and structure of (i) carboxylic acid, (ii) alcohol and (iii) the compound 'X'.
Ans: (i) The carboxylic acid is ethanoic acid.

(ii) The alcohol is ethanol.

(iii) The compound 'X' is ethyl ethanoate.

10. The electrons in the atoms of four elements A, B, C, D are distributed in three shells having 1, 3, 5, 7 electrons in the outermost shell respectively. State the period in which these elements can be placed in the modern periodic table. Write the electronic configuration of the atoms of A and D and the molecular formula of the compound formed when A and D combines.
Ans: These elements can be placed in the third period of the modern periodic table.
Electronic configuration of A - 2, 8, 1 (Na).
Electronic configuration of D - 2, 8, 7 (Cl).
The molecular formula of the compound formed when A and D combines is AD (NaCl).

11.

On the basis of the above table, answer the following questions:
(i) Name the element which forms only covalent compounds.
(ii) Name the element which is a metal with valency three.
(iii) Name the element which is a non-metal with valency three.
(iv) Out of D and E, Which one is bigger in size and why ?
(v) Write the common name for the family to which the elements C and F belong.
Ans: (i) E
(ii) D
(iii) B
(iv) D is bigger due to less electronegativity.
(v) Noble Gases

12. Explain the process of regeneration in Planaria. How is this process different from reproduction ?
Ans: If Planaria is somehow cut into many pieces, many of these pieces grow into separate individuals. This is known as regeneration. Regeneration is carried out by specialised cells which proliferate and make a large number of cells.

Regeneration is different from reproduction as most organisms would not normally depend on being cut up to be able to reproduce.

13. What is placenta ? State its function in human female.
Ans: The embryo gets nutrition from the mother's blood with the help of a special tissue. This tissue is called placenta. It contains villi on the embryo side and blood spaces on the mother side. It transfers glucose and oxygen from mother's blood to embryo and waste products from embryo to mother's blood.

14. With the help of suitable examples, explain why certain traits cannot be passed on to the next generation. What are such traits called?
Ans: The traits that do not make any changes in the germ cells cannot be passed on to the next generation. For eg. : Loss of weight due to starvation, our eating and talking habits etc. Such traits are called acquired traits.

15."A trait may be inherited but may not be expressed. Justify this statement with the help of a suitable example.
Ans: If we cross pure bred tall pea plants with pure bred dwarf pea plants, then we will have a progeny of all tall plants. Crossing the newly produced tall plants among themselves will result in a progeny of plants in which 25 % of the plants are dwarf while the rest are tall. This shows that the trait of dwarfness was inherited in the second generation but was not expressed in that generation. It was expressed in some plants of the third generation.

16. A student wants to project the image of a candle flame on a screen 60 cm in front of a mirror by keeping the flame at a distance of 15 cm from its pole.
(a) Write the type of mirror he should use.
(b) Find the linear magnification of the image produced.
(c) What is the distance between the object and its image ?
(d) Draw a ray diagram to show the image formation in this case.

Ans: (a) Concave Mirror
(b) -4
(c) 45 cm
(d)

17. Draw a ray diagram to show the path of the refracted ray in each of the following cases :
A ray of light incident on a concave lens is
(i) passing through its optical centre.
(ii) parallel to its principal axis.
(iii) directed towards its principal focus.
Ans: (i)

(ii)

(iii)

18. A narrow beam PQ of white light is passing through a glass prism ABC as shown in the diagram.

Trace it on your answer sheet and show the path of the emergent beam as observed on the screen DE.
(i) Write the name and cause of the phenomenon observed.
(ii) Where else in nature is this phenomenon observed ?
(iii) Based on this observation, state the conclusion which can be drawn about the constituents of white light.

Ans:

(i) The phenomenon is named dispersion of light which is caused because the opposite faces of prism are not parallel.
(ii) In the formation of rainbow.
(iii) White colour comprises of seven colours which are violet, indigo, blue, green, yellow, orange and red.

19. " Energy flow in a food chain is unidirectional." Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.
Ans: Energy flow in a food chain is unidirectional as the energy gone into a higher trophic level cannot come back to a lower trophic level.
Pesticides are non - biodegradable. They get washed off into water bodies where fishes eat them. When men or other organisms eat the fish, it enters the food chain. Since humans are at the top of any food chain, large amount pesticides get accumulated in their bodies.

20. Elements forming ionic compounds attain noble gas configuration by either gaining or losing electrons from their outermost shells. Give reason to explain why carbon cannot attain noble gas configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also give reason why carbon compounds are poor conductors of electricity.
Ans: Carbon cant gain 4 electrons because it would be difficult for a nucleus having only 6 protons to hold 10 electrons. Carbon cant loose 4 electrons because of energy considerations. Thus, it cant gain or loose electrons to attain a noble gas configuration.
In ionic compounds, electrovalent bonds are formed while in carbon compounds, covalent bonds are formed.
Carbon compounds don't have free electrons or ions. Thus they cant conduct electricity.

21. (a) Draw a sectional view of human female reproductive system and label the part where
(i) Eggs develop.
(ii) fertilisation takes place.
(iii) fertilised egg gets implanted.
(b) Describe, in brief, the changes the uterus undergoes
(i) to receive the zygote.
(ii) if zygote is not formed.
Ans:
(a)

(b) (i) The lining of uterus thickens and is richly supplied with blood to nourish the growing embryo.

(ii) The lining of uterus breaks and comes out through vagina as blood and mucous.

22. (a) Name the parts labelled as A, B, C, D in the diagram given below :

(b) What is pollination ? State its significance.
(c) How does fertilisation occur in flowers ? Name the parts of the flower that develop into (i) seed, and (ii) fruit after fertilisation.
Ans: (a) A is Pollen Grain, B is Pollen Tube, C is ovary and D is Female germ-cell.
(b) The transfer of pollen grains from anther to stigma is called pollination. Without pollination, fertilisation cant occur.
(c) After pollination, a pollen tubes comes out of a pollen grain through which the male germ cell goes to meet the female germ cell. Then fertilisation occurs after which ovule develops into seed and ovary into fruit.

23. (a) Explain the following terms related to spherical lenses :
(i) optical centre
(ii) centres of curvature
(iii) principal axis
(iv) aperture
(v) principal focus
(vi) focal length
(b) A converging lens has focal length of 12 cam. Calculate at what distance should the object be placed from the lens so that it forms an image at 48 cm on the other side of the lens.
Ans: (a) (i) The point on a spherical lens through which a ray of light doesn't suffer any deviation is called optical centre.
(ii) The centres of the spheres of which the lens is a part are called centres of curvature.
(iii) The line passing through the optical centre and the centres of curvature is called principal axis.
(iv) The effective diameter of the circular outline of a spherical lens it called its aperture.
(v) The rays of light parallel to principal axis after refraction pass through a point or appear to emerge from a point which is principal focus.
(vi) The distance between focus of a mirror and its optical centre is called focal length.
(b) Here,
f = 12 cm , v = 48 cm , u = ?
Using lens formula, we have :

On solving, u = - 16 cm
Thus, the object is to be placed 16 cm away from optical centre on the principal axis.

24. (a) List the parts of human eye that control the amount of light entering to it. Explain how they perform this function.
(b) Write the function of retina in human eye.
(c) Do you know that corneal - impairment can be cured by replacing the defective cornea with the cornea of the donated eye ? How and why should we organise groups to motivate the community members to donate their eyes after death ?
Ans: (a) Iris and pupil control the amount of light entering to eye. Pupil is a hole in iris. The iris stretches or relaxes itself to change the size of pupil which subsequently results in the regulation of amount of light entering the eye.
(b) The retina acts as a screen for the eye lens.
(c) [This question is a value based question and can have multiple answers. Students are required to answer this question on their own.]

SECTION B

25. In an experiment to study the properties of ethanoic acid, a student takes about 3 mL of ethanoic acid in a dry test tube. He adds an equal amount of distilled water to it and shakes the test tube well. After some time he is likely to observe that

(A) a colloid is formed in the test tube.

(B) the ethanoic acid dissolves readily in water.

(D) water floats over the surface of ethanoic acid.

Ans: (B)

26. A student takes about 2 mL ethanoic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He reports the following observations.

(I) Immediately a colourless and odourless gas evolves with a brisk effervescence.

(II) The gas turns lime water milky.

(III) The gas burns with an explosion when a burning splinter is brought near it.

(IV) The gas extinguishes the burning splinter that is brought near it.

The correct observations are

(A) I, II and III

(B) II, III and IV

(D) I, II and IV

Ans: (D)

27. We need 20% aqueous solution of sodium hydroxide for the study of saponification reaction. When we open the lid of the bottle containing solid sodium hydroxide we observe it in which form?

(A) Colourless transparent beads

(B) Small white beads

(C) White pellets/flakes
(D) Fine white powder
Ans: (C)

28. While studying saponification reaction, a student measures the temperature of the reaction mixture and also finds its nature using blue/red litmus paper. On the basis of his observations the correct conclusion would be
(A) the reaction is exothermic and the reaction mixture is acidic.
(B) the reaction is endothermic and the reaction mixture is acidic.
(C) the reaction is endothermic and the reaction mixture is basic.
(D) the reaction is exothermic and the reaction mixture is basic.
Ans: (C)

29. In a locality, hard water, required for an experiment, is not available. However the following salts are available in the school laboratory :
1. Sodium Sulphate
2. Calcium Sulphate

3. Magnesium Chloride
4. Sodium Chloride
5. Calcium Chloride
6. Potassium Sulphate
Which of the above salts may be dissolved in water to obtain hard water for the experiment ?
(A) 2, 3 and 5
(B) 1, 2 and 5
(C) 1, 2, 4 and 6
(D) 3 and 5 only
Ans: (A)

30. A student has obtained an image of a well - illuminated distant object on a screen to determine the focal length, F1 of a given spherical mirror. The teacher then gave him another mirror of focal length, F2 and asked him to obtain a focussed image of the same object on the same screen. The student found that in order to focus the same object using the second mirror, he has to move the mirror away from the screen. From this observation it may be concluded that both the spherical mirror given to the student were (select the correct option)
(A) Concave and F1 < F2
(B) Concave and F1 > F2
(C) Convex and F1 < F2
(D) Convex and F1 > F2

Ans: (A)

31. A student focussed the Sun rays using an optical device 'X' on a screen S as shown.

From this it may be concluded that the device 'X' is a (select the correct option)
(A) Convex lens of focal length 10 cm
(B) Convex lens of radius of curvature 20 cm
(C) Convex lens of focal length 20cm
(D) Concave mirror of focal length 20 cm
Ans: (C)

32. After tracing the path of a ray of light passing through a rectangular glass slab for four different values of the angle of incidence, a student reported his observations in tabular form as given below :

The best observation is
(A) I
(B) II
(C) III
(D) IV
Ans: (A)

33. A student traces the path of a ray of light passing through a rectangular glass slab and marks the angle of incidence i, angle of refraction r and angle of emergence e as shown.

The correctly marked angle(s) is/are
(A) angle i only
(B) angle e only
(C) angle r only
(D) angle i and e only
Ans: (C)

34. Study the following diagrams in which the path of a ray of light passing through a glass prism as traced by four students P, Q, R and S is shown :

The student who has traced the path correctly is
(A) P
(B) Q
(C) R
(D) S
Ans: Q

35. In the following diagram, the path of a ray of light passing through a glass prism is shown :

In this diagram the angle of incidence, the angle of emergence and the angle of deviation respectively are (select the correct option) :
(A) X, R and T
(B) Y, Q and T
(C) X, Q and P
(D) Y, Q and P
Ans: (D)

36. A student is using a convex lens of focal length 10 cm to study the image formation by a convex lens for the various positions of the object. In one of his observations, he may observe that when the object is placed at a distance of 20 cm from the lens, its image is formed at (select the correct option)
(A) 20 cm on the other side of the lens and is of the same size, real and erect.
(B) 40 cm on the other side of the lens and is of magnified, real and inverted.
(C) 20 cm on the other side of the lens and is of the same size, real and inverted.
(D) 20 cm on the other side of the lens and is of the same size, virtual and erect.
Ans: (C)

37. A student is using a convex lens of focal length 18 cm to study the image formation by it for the various positions of the object. He observes that when he places the object at 27 cm, the location of the image is at 54 cm on the other side of the lens. Identify from the following diagram the three rays that are obeying the laws of refraction and may be used to draw the corresponding ray diagram.

(A) 1, 2 and 4
(B) 1,3 and 5
(C) 2, 4 and 5
(D) 2, 3 and 4
Ans: (D)

38. A student has to focus his compound microscope to observe a prepared slide showing different stages of binary fission in Amoeba. The steps hi is likely to follow are listed below in haphazard manner :
I. Adjust the diaphragm and the mirror of the microscope so that sufficient light may enter to illuminate the slide.
II. Fix the slide on the stage carefully.
III. Adjust the microscope to high power and focus.
IV. Adjust the microscope to low power and focus.
The correct sequence of the above steps to observe the slide under the microscope is
(A) I, II, IV, III
(B) II, I, IV, III
(C) II, IV, I, III
(D) I, IV, II, III
Ans: (A)

39.When you study a slide showing different stages of budding in a yeast, you observe the following stages :
I. The bud may get separated from the parent body and develop into a new individual.
II. The body of the bud develops and gives rise to another baby bud.
III. A bud comes out in any direction from the body of the parent cell.
IV. Thus they may form a colony.
The proper sequence of the above stages is
(A) II, I, III, IV
(B) II, III, I, IV
(C) III, II, I, IV
(D) III, I, II, IV
Ans: (D)

40. Study the following statements :
I. Wings of birds and wings of bats are homologous organs.
II. Wings of birds and wings of insects are modified forelimbs.
III. Wings of birds and wings of insects are analogous organs.
IV. Wings of birds and forelimbs of horse are homologous organs.
The correct statements are
(A) I and II
(B) II and III
(C) III and IV
(D) I and IV
Ans: (C)

41. Which of the following pairs of two vegetables represents the correct homologous structures ?
(A) Sweet potato and potato
(B) Sweet potato and tomato
(C) Carrot and potato
(D) Radish and carrot
Ans: (D)

42. In the following diagram showing the structure of embryo of a dicot seed, what are the parts marked I, II and III sequentially ?