Solved 10th Science Board Paper - 2014 code 31/2

1. Atomic no. of x = 12; Atomic No. of y = 16

2. The transfer of traits from parents to offspring is called heredity.

3. Paper and glass can be easily recycled but thrown in the dust bin.

4. This is because both the father and the mother contribute practically equal amounts of genetic material to the child during sexual reproduction in forming ztgote.

5. Object placed between pole and focus see in diagram:

6. Decomposer break-down the complex organic substances into simple inorganic substances. The natural replenishment of the soil also takes place by Decompose.

7. Watershed management is the study of the characteristics of a watershed. It helps to manage water quality, water supply, and drainage and rainwater flow. It also ensures sustainable maintenance planning of a watershed.

Benefits of a watershed management system:

Water quality is strictly maintained.

Distribution of water is equal and sustainable.

8. The producers convert solar energy into chemical energy in the form of organic compounds. The primary consumers (herbivores) derive their nutrition from the producers. According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other. So, the energy that is captured by the producers does not revert back to the Sun and the energy transferred to the herbivores does not come back to the producers. It just keeps on moving to the next trophic level in a unidirectional way. That is why the flow of energy in the food chain is always unidirectional.

A large number of pesticides and chemicals are used to protect our crops from pests and diseases. Some of these chemicals are washed down from the soil, while some enter the water bodies. From the soil, they are absorbed by plants along with water and minerals; and from the water bodies, they are taken up by aquatic plants and animals. This is how these chemicals enter the food chain. As these chemicals cannot decompose, they accumulate progressively at each trophic level. This increase in the concentration of harmful chemicals with each step of the food chain is called biomagnification. As human beings occupy the top level in any food chain, these chemicals get accumulated in our bodies.

10. (a) He should use a concave mirror, as it forms a real image on the same side of the mirror.
(b) Object distance, u = -12 cm
image distance, v = - 48 cm
Magnification, m = -vu = -(-48)(-12) = -4
The minus sign in magnification shows that the image formed is real and inverted.
(c) The image is formed at a distance of 36 cm from the object.
(d) In this case, the image is formed beyond the centre of curvature. This image is real, inverted and enlarged.

11. (i) The phenomena of the splitting of the white light into its constituents colours is called dispersion of the light. Therefore, the phenomena observed is dispersion of light.

The dispersion of light is caused, because different constituent colours of light offers different refractive index to the material of the prism.

(ii) The formation of rainbow is caused by the dispersion of white sunlight into its constituents colours.

(iii) Based on the dispersion of white light into its constituent colours we conclude that:

(a) White light consists of seven colours.

(b) The violet light suffers the maximum deviation and red light suffers the minimum deviation

12. Given:
C2H4O2 + RCH2OH →H+X

RCH2OH →H+KMnO4 C2H4O2


Chemical reactions involved:

CH3COOH + C2H5OH → H+ CH3COOC2H5 C2H4O2 Alcohol X C2H5OH →H+KMnO4 CH3COOHAlcohol

(i) The carboxylic acid involved in the reaction is acetic acid (CH3COOH).
(ii) The alcohol involved in the reaction is ethanol (CH3CH2OH).
(iii) X is the ester formed by the condensation of acetic acid, and ethanol is ethyl acetate (CH3COOC2H5)
MCQS
25. (C) Convex lens of focal length 20 cm.

26. (B) Concave and F1 > F2

27. (D) 2, 3 and 4

28. (C) 20 cm on the other side of the lens and is of the same size, real and inverted.

29. (D) Y, Q and P

30. (B) Q

31. (C) ∠r only

32. (C) III

33. (A) Plumule, Cotyledon, Radicle

34. (D) Radish and carrot

35. (C) III and IV

36. (C) III, II, I, IV

37. (B) II, I, IV, III

38. (A) 2, 3 and 5

39. (D) I, II and IV

40. (B) the ethanoic acid dissolves readily in water.

41. (C) White pellets/flakes

42. (A) the reaction is exothermic and the reaction mixture is acidic.