Class 8 Science: Sample Question Paper - 12 | Science Class 8 PDF Download

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Class - VIII
Science Theory
TIME: 3 Hrs.
M.M: 80

General Instructions:
1. Attempt all the questions and follow the instructions given in each question.
2. Q.1 Multiple Choice Question (1 × 10 = 10 Mark)
3. Q.2 Very Short Answer Type Questions (1 × 6 = 6 Marks)
4. Q.3 to Q.9 Short Answer Type Questions-I (2 × 7= 14 Marks)
5. Q.10 to Q.19Short Answer Type Questions-II (3 × 10 = 30 Marks)
6. Q.19 to Q.23 Long Answer Type Questions (5 × 4 = 20 Marks)

Q.1. Choose the correct option :
(i) Which of the following is not likely to cause Tsunami?
(a) A major nuclear explosion undersea
(b) Earthquake
(c) Volcanic eruption
(d) Lightning
Ans: d

(ii) Which of the following statements is correct regarding rods and cones in the human eye?
(a) Cones are sensitive to dim light
(b) Cones are sensitive to bright light
(c) Rods are sensitive to bright light
(d) Rods can sense colour.
Ans:  b

(iii) Which of the following is NOT a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
Ans:  a

(iv) Which of the following is not a source of air pollution?
(a) automobile exhaust
(b) burning of firewood
(c) Windmill
(d) power plant
Ans:  c

(v) Which of the following is not a traditional irrigation method?
(a) Moat
(b) Chain pump
(c) Drip system
(d) Rehat
Ans: c

(vi) Which of the following is an antibiotic?
(a) Sodium bicarbonate
(b) Streptomycin
(c) Alcohol
(d) Yeast
Ans:  b

(vii) Typhoid is a  _______________ disease.
(a) protozoan
(b) viral
(c) bacterial
(d) fungal
Ans: c

(viii) The most suitable material for the preparation of handles of cooking utensils is
(a) Polythene
(b) PVC
(c) Nylon
(d) Bakelite
Ans: d

(ix) Which of the following can be beaten into their sheets?
(a) Silver
(b) Phosphorus
(c) Sulphur
(d) Oxygen
Ans: a 

(x) PCRA stands for
(a) Public Conservation Research Association
(b) Petroleum Conservation Research Association
(c) Public Council of Research Association
(d) Partial Counting of Remaining Amendments
Ans: b

Q.2. (i) Write two physical properties of metals.
Ans: Ductility and Sonority
(ii) Define pressure and write its formula.
Ans: The force acting on a unit surface area is called pressure.
Formula : Pressure = Force/Area
(iii) Name the part of the eye that gives colour to the eye.
Ans: Iris has different colours, so the iris gives its colour to the eyes.
(iv) What is the other name of the voice box?
Ans: Larynx
(v) Name the force that always opposes the applied force.
Ans: Frictional force
(vi) Name the layer present outside the cell membrane in the plant cell.
Ans: Cell wall

Q.3. What are the uses of plastic in the healthcare industry?
Ans: Plastics find extensive use in the healthcare industry. Some examples of their uses are the packaging of tablets, threads used for stitching wounds, syringes, doctor’s gloves, and many medical instruments.

Q.4. Give reason :
(i) Sulphuric acid is poured on a Zinc plate.
(ii) Write the word equation of the reaction involved.
Ans: (i) Zinc  plate reacts with sulphuric acid and forms zinc sulphate and hydrogen gas.
(ii)Zinc (solid) + Sulfuric acid (aqueous) → Zinc sulfate (aqueous) + Hydrogen gas

Q.5. Where is oil found in India?
Ans: Oil is found in India in Assam, Gujarat and Mumbai High and the Godavari and Krishna's river basin.

Q.6. (i) Name the tool used with a tractor for sowing seeds in the field.
(ii) What is the advantage of using this tool?
Ans: (i) The tractor's tool for sowing seeds in the field is a drill.
(ii) It protects the seeds from the damage caused by birds.

Q.7. In an experiment, 4.5 kg of fuel was completely burnt. The heat produced was measured to be 1,80,000 kJ. Calculate the calorific value of the fuel.
Ans: Given : Mass of fuel = 4.5 kg
The heat produced by combustion of 4.5 kg of fuel = 1, 80, 000 kJ
So, the calorific value of fuel = Heat produced by combustion of 1 kg of fuel
 = 40, 000 kJ/kg.

Q.8. Name the virus that causes AIDS. What are the mediums through which this virus is transmitted?
Ans: AIDS is caused by a virus named HIV. It can be transmitted from an infected person to a healthy person in the following ways :
(i) By infected syringes.
(ii) By infected mother to an infant.
(iii) By sexual contact with the infected person.

Q.9. Explain internal fertilisation.
Ans: Fertilisation that takes place inside the female body, is called internal fertilisation. Internal fertilisation occurs in many animals, including cows, dogs and hens.

Q.10. What is the full form of CNG and LPG?
Ans: CNG: Compressed Natural Gas.
LPG:  Liquefied Petroleum Gas.

Q.11. Cartilage is present in our body joints, which helps in their smooth movement. With advancing age, this cartilage wears off. How would this affect the movement of joints?
Ans: Cartilage is present in the joints of our body reduces friction during the movement of joints. But on wearing off of this cartilage, the force of friction increases, due to which the smoothness of movement decreases, and one feels the joint pain.

Q.12. Why do we not hear the sound of an explosion on the surface of the moon?
Ans: There is no atmosphere on the moon, and sound waves need a medium to travel. So we cannot hear the sound on the moon.

Q.13. Fill in the blanks with most appropriate answer :
(a) The fish like baby of a frog ___________.
(b) The animal that lay thousand of eggs ___________.
(c) The stage of the embryo in which all the body parts can be identified ___________.
Ans: (a) Tadpole
(b) Fish/Lice
(c) Foetus

Q.14. (i) Differentiate between an asteroid and a comet.
(ii) (a) The planet which is farthest from the Sun is ________.
(b) The planet which appears reddish in colour _________.
Ans: (i) Asteroid: The gap between Mars and Jupiter is occupied by a large number of objects that revolve around the sun.
Comet: They revolve around the sun in more elliptical orbits 
(ii) (a) Neptune(b) Mars

Q.15. Give reason :
The powder is sprinkled on the carrom board before playing.
Ans: We sprinkle the powder on the carrom board to smooth the board's surface. This reduces the friction between the carrom board's surface, the striker, and the coins. As a result, the coins and the striker can move easily on the carrom board.

Q.16. Give reason :
Sports people wear shoes with spikes.
Ans: Sportsmen use shoes with spikes because they give them a better grip while running. This is because the force of friction between the shoes and the ground increases with spikes' help.

Q.17. Mercury is the only metal found in the liquid state. It is largely used in thermometers to measure temperature. But mercury is a hazardous metal as its density is very high. What two precautions would you take while handling the equipment containing mercury?
Ans: Precautions while handling the equipment containing mercury are :
(i) Mercury, liquid metal with high density, can corrode the skin if it drops over it. Hence, the vessel should be closed or tightly packed.
(ii) It should not be heated directly.

Q.18. The level of air pollution is higher in metro cities. Mention the major causes responsible for this increase.
Ans: Major causes of air pollution are :
(i) Emissions from automobile exhaust.
(ii) Effluents from thermal power plants.
(iii) Smoke from forest fires, volcanic eruptions etc.

Q.19. Draw the life cycle of the Frog.
Ans: Life Cycle of Frog

Q.20. Corrosion is a serious problem. Every year an enormous amount of money is spent on replacing damaged iron. What steps can be taken to prevent this damage?
Ans: The wasting of iron objects due to rusting causes a big loss to the country’s economy; the following methods must prevent it:
(i) By painting: Paint is applied to the surface of an iron object, then air and moisture cannot come in contact with iron, and hence no rusting occurs.
(ii) By applying grease or oil: Tools and machine parts made of iron and steel are smeared with grease or oil to prevent rust.
(iii) By galvanization: Galvanization is done by dipping an iron object in molten zinc metal. This thin layer of zinc metal on the surface of iron objects protects them from rusting.
(iv) By tin plating and chromium-plating: When a thin layer of tin metal is deposited on iron and steel objects by electroplating, the iron and steel objects are protected from rusting.
(v) By alloying it to make stainless steel: When iron is alloyed with chromium and nickel, stainless steel is obtained, which does not rust at all. 

Q.21. Read the passage and answer the given question. Sarvesh noticed that during the rainy season, the plants' leaves in his school get burnt. His teacher told him that all this is due to acid rain.
(a) What is acid rain?
(b) What are the harmful effects of acid rain.
(c) What efforts can you make to reduce this acid rain?
Ans: (a) The gases such as sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) react with water vapour in the atmosphere to form sulphuric acid and nitric acid and constitute acid rain.
(b) The harmful effects of acid rain are as follows :
(i) It harms the plant life, as leaves and other parts of the plant get burnt.
(ii) It corrodes the marbles (CaCO₃) of the monuments, which results in its yellowing.
(iii) It affects animal life also.
(c) (i) We can use cleaner fuels like LPG and CNG.
(ii) Chimneys should be well equipped with air filters.

Q.22. Explain the functions of plastids.
Ans:

• The small coloured bodies in the cytoplasm are called plastids.
• These are found only in plant cells but not in animal cells.
• Plastids are of different colours.
• Some of them contain a green pigment called chlorophyll.
• The plastids having colours other than green colour are called chromoplast.
• Some plastids are colourless and are called leucoplast.
• These coloured plastids provide various colours for flowers and fruits.
• The chloroplasts having chlorophyll help in the formation of food by leaves through photosynthesis.

Q.23. Is deforestation associated with global warming? Explain.
Ans:

• Trees use carbon dioxide gas from the atmosphere for food making called ‘Photosynthesis’.
• When many trees are cut down during deforestation, then a lesser number of trees will be left.
• The lesser number of trees will use up less carbon dioxide, due to which the amount of carbon dioxide in the atmosphere will increase.
• In this way, deforestation increases the carbon dioxide level in the atmosphere.
• Carbon dioxide gas traps the sun’s heat rays reflected by the earth (causing the greenhouse effect).
• The trapping of heat rays by carbon dioxide increases the temperature of the earth’s atmosphere.
• This will lead to global warming.
• The gradual increase in the overall temperature of the earth’s atmosphere due to the greenhouse effect caused by the increased level of carbon dioxide in the atmosphere is called global warming.