ASWER KEY-CODE- IXZ
CLASS X
TIME : 3H SCIENCE
M
M : 80
Marking Scheme
1. Ethane, hydrogenation ½, 1/2
2. Properties of elements are periodic functions of their atomic number 1
3.(a) Pollution free,
low cost, eco-friendly, no large space for storage, no long transportation
(any other two points)
1
(b) From cow dung gas is produced by the anaerobic respiration
by bacteria. 1
(c) High cattle population, no shortage of cow dung, (any
other two) 1
(d) Low cost gas available,
surroundings clean, residue used as manure (any two) 1
4(a)Any two symptoms
1
(b)Neck, around the trachea
1
(c) Thyroxin, regulate carbohydrate, protein and fat
metabolism
1
(d) Iodine is essential for the synthesis of thyroxin. 1
5. c OR c
1
6. d
1
7. c 1
8. c OR c 1
9. a 1
10. d 1
11. a 1
12. c OR c 1
13. (iii)
1
14. (i)
1
15.(a) X is zinc 1/2
(b)Y is copper
1/2
(c)YSO4 is CuSO 4 1/2
(d) displacement reaction, Zn + CuSO4 ------->ZnSO4 +
Cu 1
(e) brass
½
16.(a) Vinegar- less than
7, turns blue litmus red
1
(b)Milk of magnesia - more than 7, turns red litmus blue 1
(c)Stomach juices -less than
7, turns blue litmus red. 1
OR
Na2CO3 is a salt of strong base and
weak acid 1/2
Na2CO3
+ H2O -------->
2NaOH + H2CO3
(strong base) ( weak acid) 1
(strong base) ( weak acid) 1
NH4Cl is a salt of weak base and strong acid ½
NH4Cl
+ H2O ----------> NH4OH +
HCl 1
(
weak base) (strong
acid)
17. (a) A is a
non-metal, 2,8,7 will take I electron ½, 1/2
(b) C is less
reactive than A.
1/2
In groups reactivity of non-metals decreases while going down. 1/2
(c) C is smaller
than B.
In periods atomic size decreases from left to right. 1/2,
½
18. (a) Phytoplankton
---> Zooplankton --->
Small fish ---> Large fish 1
(b) Grass --->
Goat ---> Man 1
(c) Grass
---> Grasshopper --->
Frog ---> Snake
---> Peacock. 1
OR
(a) No control over population of deer, will eat all grass
(any other two) 1
(b)Lion will die due to starvation, no control over the growth
of grass, (any other) 1
(c) Grass ----------> Deer
--------> Lion 1
200 J (1% of 20,000) 20 J 2 J
19. HCl , one function
1/2, ½
Pepsin , one function
½, ½
Mucus, one function ½,
½
20.(a) Parents GG
X gg
Gametes
G X g
------> Gg G
dominant – all green stemmed 1
(b) G g
|
GG
|
Gg
|
|
Gg
|
Gg
|
G
g
g
1 : 2 : 1, 25%
1
(c) GG – 25%, Gg-
50%. Thus, the ratio is 1 : 2 in F2
generation. 1
21. (any three) 1
x 3
|
Nervous mechanism
|
Hormonal mechanism
|
|
1. Comprises nerve impulses between peripheral nervous system,
central nervous system and brain.
|
1. Comprises endocrine system which secretes hormones directly into
blood.
|
|
2. Response time is very short.
|
2. Response time is very long.
|
|
3. Nerve impulses are not specific in their action
|
3.Each hormone has specific actions.
|
|
4. The flow of information is rapid.
|
4.The flow of information is very slow
|
22. Very high melting point, high flexibility, low rate of
evaporation at high temperature. (any two points)
1
(b) I2Rt=100 J,
I2R = 100,
I2 = !00/4 = 25, I =
5 A 1
V = IR = 5 x
4 = 20 v
1
23. (i) State Right Hand Thumb rule 1
(ii) State Fleming’s
Left Hand rule 1
(iii) State Fleming’s Right Hand rule 1
24. (a) Refer NCERT Science text book Fig. 11.5 2
(b) No scattering of light at such heights. 1
OR
(a) Refer NCERT Science text book Fig. 11.6
2
(b)Red is least scattered by fog or smoke.
So, can be seen in
the same colour at a distance 1
25.(a) Roasting : Heating in the presence of excess of air,
generally for sulphide ores.
Calcination : Heating
in the absence of air or limited supply of air,
generally done for carbonate ores.
1
(b)Mercury, Hg
1
(c) Cinnabar,
HgS
1
(d) HgS heated in air, converted in to HgO. By further heating
HgO is reduced to Hg. 1
Equations from NCERT Science text book page No.51 1
OR
(a) It is easier to obtain metals from their oxides.
(b) Mg is highly reactive, carbon can not reduce it.
(c) Zn is more reactive than copper.
(d)Bubbles of hydrogen formed stick to the surface of these
metals.
(e)Oxygen of air reacts with Al to form a thick but tough protective layer
of Al2O3 on its surface which resists the action of air.
1
x 5
26. (a) C- ethanoic acid,
R - sodium ethanoate,
A – methanol, S – ester
(methyl ethanoate), G – hydrogen gas. 1/2
x 5
(b) (i) 2CH3COOH + 2
Na ----------> 2CH3COONa + H2 ½
(C) (R) (G)
(C) (R) (G)
(ii) CH3COOH + CH3OH ----------->CH3COOCH3 +
H2O ½
(C) (A) (S)
(C) (A) (S)
(iii) CH3COOH
+ NaOH -------------> CH3COONa
(C) (R) ½
(C) (R) ½
(iv) CH3COOCH3 +
NaOH ------------->CH3COONa + CH3OH 1
(S) (R)
(S) (R)
27. (a) (i) A - Blood
(ii) B - Haemoglobin
(iii) C - Red 1/2 x 3
(b) (i) D – WBC (ii)
E – Platelets (iii) F – Plasma (iv) G – RBC
1/2 x 4
(c) Digested food,
hormones ( any one) 1/2
(d) E –
Platelets and G – RBC 1/2 x2
28. (a) Diagram, refer NCERT Science text book Fig.
8.11 2
(i) vagina (ii)
ovary (iii) Oviduct (iv)
uterus 1/2
x 4
(b) (i) 23 (ii) 46
1/2
x2
OR
(a)Diagram, refer NCERT Science text book, stamen from Fig.
8.7 1
(b) Diagram, refer NCERT Science text book, pistil from Fig.
8.7 1
(c) (i) anther – pollen 1/2
(ii) ovary –
ovule
1/2
(d) Any two points of differences 1x2
29. (a) Diagram
11/2
(b) (i) I1
= 6/5 = 1.2 A ½
I2 = 6/10 = 0.6 A ½
I3 = 6/30 = 0.2 A ½
(ii) I = I1 + I2 + I3 = 2 A 1
(iii) R = V/I =
6/2 =3 Ohm 1
30. (a) First – Position of the object between C and F,
Image away from C 2
Second – Position of the object between P and F,
image behind the mirror.
2
(b)Circumstance second, virtual image is formed behind
the mirror 1
OR
(a). Definition
½
(b. )Dioptre,
definition
1/2 + ½
(c). P = P1 +
P2 + P3 1/2
P1 =
100/20 = 5 D ½
P2 = 100/40 = 2.5 D 1/2
P3 = 100/ -50 = -2 D ½
P = 5 + 2.5 – 2 = 5.5 D ½
f = 1/P =100/5.5 =
18.18 cm 1
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