SSLC SCIENCE HOT MODEL QUESTION PAPER - 1
KEY ANSWER
PART - A PHYSICS
I. MCQs - Answer
1. A] 100Ω
2. C] 1.5cm
3. D] Dioptre
II. One Mark - Answer
4. If one Coulomb of charge passes through a conductor in one second, the current is said to be one ampere.
5. By placing a compass needle near the current carrying conductor. The deflection of the needle shows the presence of a magnetic field.
6. Rear view mirrors of vehicles are convex mirrors. They produce diminished but laterally inverted images. It helps to read the word AMBULANCE correctly for the drivers of vehicles ahead of the ambulance so that they can allow the ambulance to overtake them
III. Two Marks - Answer
7.
8. The correct refracted ray is 'OB' , When a ray of light travels from a denser medium to a rarer medium, it bends away from the normal (water to air). The ray 'OA' is not correct because CO and OA are in the same straight line, and cannot represent refraction
IV. Three Marks - Answers
9.
As shown in the diagram, when a magnet is moved inside a coil, there will be a deflection in the galvanometer. There will be deflection again when the magnet is moved out of the coil. There will not be any deflection if both the coil and the magnet are stationary. From this experiment Faraday concluded that whenever there is change in the magnetic field, there will be an induced emf in the coil.
As shown in the diagram, coil - 1 is connected to a battery and it acts like an electromagnet. There will be deflection
in the galvanometer connected to coil - 2 when the key is switched on or off. Each time the deflection will be on either side of the O (zero) mark on galvanometer. There will not be any deflection when the plug key of coil- 1 is closed for a long time because magnetic field of coil- 1 does not change (stationary magnet field). To get deflection in the galvanometer, coil - 2 should be under the influence of a changing magnetic field To change the magnetic field, the circuit of coil-1 should be repeatedlyswitched off and on.
10. Construction of dams for hydroelectric power plants results in losing agricultural land, shifting human eco-systems habitation and destruction of forests. Large areas of land are submerged. Large ecosystem are destroyed. The vegetation under the submerged area rots due to an-aerobic conditions and produces greenhouse gases such as methane.
OR
The major constituent of biogas is methane Biogas plants have the following advantages:
a] Biogas is a renewable formof energy for which raw materials such as animal dung, waste vegetables etc. are readily available
b] It helps in the decentralisation ot energy sources, thus avoiding transportation losses
d] Community biogas plants can meet the energy requirement of some families locally.
d] Methane is a clean fuel.
e] The spent slurry of biogas plants can be directly used as manure, as it is rich in phosphorus.
f] Advanced technology is not necessary for setting up a biogas plant.
11. A concave mirror produces a real inverted image if the object is placed at a distance which is greater than its focal length. The person observed an inverted image of his face because he held the mirror at a distance of more than 10 cm from his face. He can avoid this situation by holding the mirror at a distance less than 10 cm from his face.
OR
Given:
f = 20cm
u= -40cm
v=?
Lens Formula.
I/f = 1/v - 1/u
1/v = 1/f + 1/u
= 1/20 + 1/-40
= 1/40
v = 40cm
m = u/v
= 40/-40
m = -1
:. Height of the image is the same as that of the object, i.e., 4 cm, real and inverted
V. Four Marks - Answer
12. a] Comparatively the resistivity of silver is less than that of other metals used for wires, such as copper or aluminium. If silver is used for interconnecting solar cells, power loss in the interconnecting wires can be minimised.
b] During transmission of electricity from one town to another, power loss due to resistance of the wire will occur. If thick cables are used, their resistance is less and power loss can be minimised. This happens because resistance is inversely proportional to the area of cross section of the wire.
e] p= V²/R. Power of an electric filament bulb is inversely proportional to its resistance. For this reason bulbs with higher rating [60 WJ have filament with lower resistance than bulbs with lower rating [40 W].
d] Heating elements have power ratings between 1-2 KW, whereas lighting elements have much lesser power ratings.
As p= VI, ampere rating of a fuse is given by power/ voltag. Hence, fuse wires of different ampere ratings should
Be used for lighting and heating circuits.
VI. FIVE MARKS-ANSWER
13] a] During daytime the atmospheric particles scatter lower wavelength (higher frequency) of the sunlight due to Rayleigh scattering. Blue light has lower wavelength and it is scattered more. So the sky appears blue.
b] After a spell of rain, some of the tiny water drops remain suspended in air. These tiny drops act like water prisms and disperse the colours of the sunlight (white light) into a Spectrum. The spectrum appears as a rainbow in the direction opposite to the sun.
c] Stars appear as point sources of light due to their great distance from the Earth. The light passes through many layers of atmosphere of different optical densities. Before reaching our eyes the starlight undergoes multiple refractions. and hence stars appear to be twinkling
due to the apparent shift in position.
d] Early sunrise is also an effect of atmospheric refraction. The sun rises two minutes before the actual sunrise due to bending of the Sun's rays by Earth's atmosphere. Due to this, we see the sun at an apparent position and not its actual position, as shown in the figure.
e] The path of a light can be seen when the light is scattered by colloidal particles of smoke or of dust due to Tyndall effect.
PART - B CHEMISTRY
VII. MCQs - ANSWERS
14. B] HgO
15. C] C2H5OH
16. D] Na2O3
VIII. ONE MARK - ANSWERS
17] The oxidation of glucose in our body produces heat energy. Thus, it is an exothermic reaction.
18] An insoluble substance produced during a chemical reaction is called a precipitate. Such reactions are precipitate reactions.
19. Galvanisation consists of coating zinc metal on iron and other metals which may get corroded in contact with air and moisture . It is done to prevent rusting and corrosion .
IX. TWO MARKS - ANSWERS
20] Sodium: 2,8, 1, Chlorine: 2,8,7
OR
Molten sodium chloride contains Na+ and Cl- ions.
At the cathode Na+ + 1e- → Na.
At the anode Cl- - 1 e- → Cl.
21.
23. When sulphur powder and carbon powder are burnt in air they combine with oxygen in the air, producing oxides due to the following reactions:
S+02 → S02
C+O2 → CO2
These oxides are non-metallic oxides. When they are dissolved in water present in the wet litmus paper they produce sulphurous acid and carbonic acid respectively. Blue litmus turns red and red litmus does not change in colour. The conclusion that can be drawn is that non-metallic oxides which are soluble in water are acidic in aqueous solutions.
OR
a] Highest amount of hydroxyl ions [OH-] are present in sodium hydroxide as it is a base.
b] Highest amount of hydronium ions [H30+] are present in hydrochloric acid because when compared to ethanoic acid, hydrochloric acid is a strong acid.
c] Lowest amount of hydronium ions [H3O+] are present in Ethanoic acid as it is a weak acid.
d] The solution of sodium chloride contains equal amount of H+and H3O+ ions as it is a neutral salt solution.
On pH scale we can place them as follows.
24. a ] CnCH2n+1COOH n=15 there fore C15CH31COOHb] CnCH2n-1COOH n=15 there fore C15CH29COOH
c] CnCH2n-3COOH n=15 there fore C15CH27COOH
C15CH31COOH is saturated because it is obtained from alkane .
C15CH29COOH is unsaturated because it is obtained from alkene .
C15CH27COOH is also unsaturated because it is obtained from alkyne .
25. a] 2AgNO3 + Cu → Cu (NO3)2 + 2Ag
sunlight
b] 2AgCl → 2Ag + Cl₂
c ] BaCl₂ + H₂SO4 → BaSO4 ↓ + 2HCl
PART - C BIOLOGY
XI. MCQs - ANSWERS
26. D] 46
27. D] Left ventricle pumps oxygenated blood.
XIl. ONE MARK - ANSWERS
28. Hormones are chemical messengers that are secreted directly into the blood, which carries them to organs and tissues to influence their functioning.
29. All the interacting organisms in an area together with the non-living constituents of the environment form what is called an eco-system
XIII. TWO MARKS - ANSWERS
30.
31] Sex determination is illegal and punishable because, under law, both the genders are equal. Such notices are put up in a scanning centre as sex determination is wrongly used to know the sex of the foetus and abort it if it is a female foetus. Because of this, sex ratio (ratio of females to males) is decreasing. By enacting such laws, the government wants to maintain equality of male and female members in the population.OR
Mendel used a dihybrid cross between pure pea plants to show that traits are inherited independently. He selected pea plants with yellow round seeds (YYRR) and crossed them with green wrinkled seeds (yyrr). In F, generation, the plants had round yellow seeds (YyRr). F2 generation is represented as follows:
9 Yellow and Round 3 Yellow and Wrinkled3 Green and Round 1 Green and Wrinkled
This shows that the two characteristics 'R and 'y' are not linked to each other. So they are independently inherited.
32.
XIV. THREE MARKS - ANSWERS
33. Construction of large dams should be opposed because it gives rise to the following problems:a] Social problems such as the displacement of a large number of peasants and tribals without adequate compensation or rehabilitation. People who are displaced due to execution of various development projects are largely poor tribals who do not get any benefits from these projects.
b] Economic problems because they swallow up huge amounts of public money without the proportionate benefits.
c] Environmental problems because they contribute enormously to deforestaton and the loss of biological diversity.
34.
XV. FOUR MARKS - ANSWERS36.
37.
The human brain has 3 major regions,
a] Fore-brain
b] Mid-brain c] Hind brain
i] Fore-brain is the main thinking part of the brain.
ii] The cerebrum is the largest part of the brain. It is made up of two cerebral hemispheres, their cortices and the underlying regions of white matter.
iii] The medulla oblongata is a long stem-like structure located in the brain stem.
iv] The hypothalamus is a small region of the brain, located at its base, near the pituitary gland. It regulates emotional responses.
v] The pituitary gland is a part of our endocrine system. Its main function is to secrete hormones into the bloodstream. These hormones can affect other organs and glands, especially the thyroid and adrenal glands.
38. Mendel selected pea plants with single pair of contrasting characteristics for his experiment. He selected a tall plant with genotype TT and a dwarf plant with genotype tt. These plants were pollinated and the offsprings were obtained. The offsprings of F1 generation were all tall plants with genotype Tt.
The F1 generation plants with genotype Tt were crossed and F2 generation plants were obtained. Both tall and dwarf plants were obtained in F, generation in the ratio 3:1. This ratio is called the monohybrid cross ratio. A single pair of contrasting characteristics was considered in this experiment, the characteristics being tall and dwarf.
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