KENDRIYA VIDYALAYA SANGATHAN HYDERABAD REGION
ANSWER KEY - 7
CLASS-X SUBJECT – SCIENCE
SECTION – A
Ans. 1. b Ans. 11. a
Ans. 2. b Ans. 12. c
Ans. 3. d Ans. 13. c
Ans. 4. c Ans. 14. a
Ans. 5. c Ans. 15. d
Ans. 6. c Ans. 16. a
Ans. 7. a Ans. 17. a
Ans. 8.d Ans. 18. d
Ans. 9. a Ans. 19. a
Ans. 10. d Ans. 20. a (1*20=20)
SECTION – B
Ans. 21. Reflexes are very sudden, automatic & unconscious response of the body parts towards
stimuli. (0.5+1.5=2)
Ans. 22. Given: I=5A V= 220V
a. Power (P )= V X I = 220V X 5A
=1100VA = 1100W
= 1.1KW
a. Electrical energy consumed E= P x t = 1.1 x 2h=2.2kWh. (1+1=2)
OR
i) Rs=R2+R3+R4 =6+8+2=16 Ohm
ii) 1/Rp=1/R1+1/Rs
=1/4 + 1/16
1/Rp=4+1/16
1/Rp =5/16
Rp= 16/5 =3.2 Ohm (1+1=2)
Ans. 23.a. Thermal Decomposition: Energy supplied in the form of heat. CaCO3------CaO + CO2
b. Photolytic
Decomposition : Energy is supplied in the form of light.2AgCl- 2Ag + Cl2 (1+1=2)
Ans. 24. a. Ozone gas b. CFCs- Chloro Fluoro Carbons c. Ozone layer acts as a protective
shield and protect us from harmful UV rays of the sun. (1/2+1/2+1=2)
Ans. 25. Organs of human excretory system are: Kidney, ureter, Urinary bladder &
urethra(1/2*4=2) Ans. 26. (Any two points) (1+1=2)
a. Alveoli are tiny balloon like structures present in millions of number.
b. They provide large surface area for exchange of gases.
c. They are richly supplied with blood capillaries.
SECTION- C
Ans. 27.a). Silver is highly malleable metal b). Silver is one of the most lustrous metal.
c). Silver is best conductor of electricity. (1+1+1=3)
Ans. 28. a). Amount of energy available to Grass (1%) = 10000* 1/100=100kJ (1.5+1/2+1=3)
Amount of energy available to Deer (10%) = 100* 10/100 =10kJ
Amount of energy available to Tiger (10%) = 10* 10/100 = 1kJ
b). Secondary Consumer (Carnivore)
c). Mushrooms act as decomposers and help in decomposing the organic matter into humus.
Ans. 29.Given: ho =5 cm u = -20 cm R =30 cm f =R/2=30/2=15 cm
a). 1/f = 1/v + 1/v b). m=hi/ho = -v/u
1/v = 1/f -1/u hi = -v * ho/u
1/v = 1/15 – 1/-20 hi = - 60/7 * 5/-20
1/v = 1/15+ 1/20 hi = 2.14 cm
1/v = 4+3/60
1/v = 7/60 c). Nature: Virtual & erect and smaller
V =60/7 =8.57cm (1.5+1+1/2=3)
Ans.30. a). The circulation of blood two times through the heart in one cycle.
OR
The following events occur during photosynthesis: (1+1+1=3)
a. Absorption of light energy by chlorophyll (Light reaction).
b. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen
and oxygen (Photolysis).
c. Reduction of Carbon dioxide to carbohydrates(Dark reaction).
Ans. 31. a. N b. ii c. i (1+1+1=3)
Ans. 32.a. Hypermetropia (far sightedness)(1+2+1+1=5)
a. Causes(any two): Shortening of eye ball, Increase in focal length of eye lens, Image is formed
beyond retina.
b. Correction: Using Convex lens of suitable focal length.
Ans. 33.Characteristics of Magnetic fieldlines (any two): (2+1=3)
a. They always originate from North Pole of the magnet.
b. They are closed concentric circles.
b. They never intersect each other at any point.
c. They have both magnitude and direction (vector) at any point on the field.
SECTION - D
Ans.34.a. This statement is true because the sex of the child is determined by the sex chromosomes. If
a sperm carrying X chromosomes fertilises an ovum, it is a female child and it will a male
child only when a sperm carrying Y chromosome fertilises an ovum, Therefore ,it is totally
a matter of chance that which sperm fertilises an ovum. (1.5+2+1/2+1/2+1/2=5)
b.i. genotype ratio: 4: 0 (Purple : White)
ii. Monohybrid cross
iii. Purple coloured flower
iv. % of Purple flowers in F2= 3/4*100
=75%
Ans.35.a (2+1+1+1=5)
b. Ionic Bonding ( Electrovalent bonding)
c. Due to the presence of ions.
d. Ionic compounds have strong force of attraction between the oppositely charged ions.
Ans.36.a. (3+1+1=5)
b). i. B ii. A
SECTION – E
Ans. 37. a). Ethanoic acid (1+1+1+1=4)
b).
a. S= Ethyl ethanoate (ester)
b. CH3COOH + C2H5OH-----CH3COOC2H5 + H2O
Ans. 38. a). Current(I) is directly proportional to Potential difference(V). Current increases with
increases with Voltage (V/I=R) (1+1+1+1=4)
b.Yes c. iii. D. Ammeter
Ans.39.a). Binary fission b). Yes c). iii. d). Spirogyra
