MARKING SCHEME X- SCIENCE (2016-17) SECTION -A
1. Single covalent bonds 1
2. F = R/2 1
3. The government launched Ganga action plan 1
4. Electronic configuration = 2,8,3 ; valency = 3. 1+1
5. In self pollination pollen grains are transferred from anther to the stigma of the same flower or another flower of the same plant. It occurs in bisexual flowers. 1
In cross pollination pollen grains are transferred from anther of a flower to the stigma of another flower. It occurs in unisexual as well as in bisexual flowers 1
6. An ecosystem is a self contained unit of biotic and abiotic components.
All living organisms interact with each other and their growth, reproduction and other activites are affected by the abiotic components .Hence biotic and abiotic components are dependent on each other. 1+1
7. The 5 carbon atoms in pentane (C5H12) can be arranged in 3 different ways (with diagram). 1x3
8.
a. Li, Na, K are grouped together in group1 of periodic table. They are grouped together because all of them have 1 electron in their valency shell. Rest of the elements Cl, Br and I are grouped together in 17th group of periodic table. 2
b. Alkali Group ½+½
Halogen Group
9.a)In modern periodic table from left to right across a period, the nuclear charge increases and the tendency of element to lose electrons decreases. Thus metallic character decreases, so element X is more metallic than element Y 1 b)The electronic configuration of X is 2,8,1 and Y is 2,8,3. So valency of X is 1 and Yis3. 1
c) Yes, the statement is true because in a period from left to right, the nuclear charge increases but number of shells remain same and also force of attraction of the nucleus for the electrons increases. Hence the atomic size decreases 1
10 Any two Correct differences and diagrams 2+1
11 Correct definition of Pollination and correct diagram (NCERT fig.8.8) 1+2
12 a. Correct definition of fossils 1 b.Distribution pattern of fossils shows that the ancient fossils present in deep rocks are simple, while more recent are found in upper strata. It gives us an idea of time in history when different species were formed or became extinct or any other two importance of fossils 2
13. correct method of sex determination explanation (refer to NCERT page no.146)and correct diagram 2+1
14.Two correct differences and one example of each. 2+1
15. Correct diagram and any two uses of concave mirror. 2+ ½ + ½
16. Correct definition 1
Sol. Real image is inverted. So , magnification is negative.
THUS, m = -3=image size/object size
= -image distance/object distance = -v/u,-3 = -(v)/(-10)
-3 = v/1 , image distance = -30 cm
Negative sign shows that image is real,so it will be formed in front of the mirror. 2
17. a) Refraction, Dispersion & Total internal Reflection or any two ½ x 2 b) yes , I agree that pollution free environment will strengthen natural phenomenon like rainbow in the cities as well as village. 1 c) with given passage, the learner will be understand the fact that the urban people will have to keep their city clean and pollution free if they wish to experience some beautiful natural events like twinkling of stars, rainbow etc. 1
18. correct diagram 1
Correct labelling ½ x 2
19. correct electron dot sructures 1+1
Correct definition and application 1+1 Any one correct difference 1
20. correct definition ,oviduct or fallopian tube 1+1
Brief explanation. of three contraceptive methods 3
21. Blue colour flower plant – AA
White colour flower plant – aa
The cross involved is as follows 1½
a) In F1 generation, all plants will have blue flowers ½
b) In F2 generation 25% of flowers will be white ½
c) The ratio of AA and Aa in F2 generation will be 1(AA):2(Aa)
22. Correct definition of myopia. 1
Two causes of myopia 2
Correct diagrams 1+1
23.correct definitions 1x3
Correct ray diagram 2
24.Any three measures 3
Name of any two industries 2 SECTION B
25 .a 1
26. c 1
27. b 1
28.b 1
29.a 1
30.c 1
31.c 1
32.c 1
33.b 1
34. presence of salts of calcium and magnesium,
Insoluble sails of calcium and magnesium formed. 1+1
35 a) Hydra –budding, Amoeba –binary fission. ½ + ½
b) in hydra buds get detached on maturing while in yeast buds remain attached to the parent cell. 1
36.Full form of VIBGYOR, Phenomenon Is Dispersion Of Light. 1+1
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