Class 8 science sample paper solution
1. Cholera is caused by a ……………………..
1. Cholera is caused by a bacterium (Vibrio cholerae).
2. The process of conversion of sugar into alcohol is called nitrogen fixation. (True/false).
OR
Which is insect is the carrier of malaria-causing protozoan.?
2. The process of conversion of sugar into alcohol is called nitrogen fixation. → False
✅ Correct statement: The process of conversion of sugar into alcohol is called fermentation.
OR
The insect that carries the malaria-causing protozoan is the female Anopheles mosquito
3. If the force is applied opposite to the motion, what will happen to the speed of the object ?
OR
Define atmosphere.
3. If the force is applied opposite to the motion, the speed of the object decreases.
OR
The atmosphere is the layer of gases surrounding the Earth.
4. Name the force due to which planets revolve around the sun.
OR
Which force is responsible for the weight of objects ?
4. The force due to which planets revolve around the sun is gravitational force.
OR
The force responsible for the weight of objects is also gravitational
force.
5. Sonorous is the property of metals by which they produce......sound when struck.........
6. Name any two metals which are bad conductor of electricity.
6. Mercury and Lead.
7. Copper displaces zinc from zinc sulphate solution. (True/False). False
(Reason: Copper is less reactive than zinc, so it cannot displace zinc from zinc sulphate solution.)
8. What is the nature of oxides of metals and non metals.
Metal oxides are basic and non-metal oxides are acidic.
9. force has both ………… and ………………
Force has both magnitude and direction
10. If the force applied on the object is in the direction of its of the object decreases.(True/false)
False
(Reason: The speed increases if the force is in the same direction as motion.)
11. In a tug of war, side A applies 10 newton force and side B applies 8 newton force. Which side will the rope move ?
11. The rope will move towards side A (the side applying the greater force).
12. Does the force of friction also act on the objects moving in the air?
12. Yes
→ It is called air friction or air resistance (a type of frictional force that opposes motion through air
2. Look at the following given picture and write the name of the organism for each.
OR
Give an example of one antibiotic and the name of bacteria to produce it.
(only for visually impaired students).
2. Answer: Example of one antibiotic: Penicillin
Name of microorganism that produces it: Penicillium notatum (a fungus).
👉 (Note: Penicillin is an antibiotic discovered by Alexander Fleming, produced by the fungus Penicillium notatum.)
3.. If you have taken one 1 litre milk from the market and need to pasteurize it
at your home. How will you do it.?
OR
What are communicable diseases? Give two examples.
3. Answer:
Option 1 – Pasteurization of milk at home:
To pasteurize 1 litre of milk at home:
- Heat the milk to about 70°C for 15–30 seconds (do not boil).
- Then cool it quickly to about 10°C.
This process kills harmful germs without changing the taste of milk.
Option 2 – Communicable diseases:
Communicable diseases are diseases that spread from one person to another through air, water, food, or contact.
Examples:
- Tuberculosis (TB)
- Common cold
4. If you store the lemon pickle in an aluminium utensil at your home, then
you find that after some days, it gets spoiled? Explain why?
4. Answer:
Lemon pickle gets spoiled in an aluminium utensil because lemon contains acid (citric acid).
This acid reacts with aluminium and forms harmful salts of aluminium.
These chemical reactions spoil the pickle and make it unsafe to eat.
✅ Conclusion:
Acidic foods like pickles should never be stored in metal utensils; they should be kept in glass or plastic jars.
5. At high altitudes of mountains, sometime the people face a problem of nose
bleeding. Why?
OR
Why is easier to hammer a sharp nail into wood than a blunt one ?
5. Let’s answer both parts one by one:
(1) At high altitudes of mountains, people sometimes face nose bleeding. Why?
At high altitudes, air pressure is very low. The air is also dry.
Because of this:
- The blood vessels in the nose expand and burst easily,
- The dryness irritates the nasal passages,
So, nose bleeding occurs due to low atmospheric pressure and dryness at high altitudes.
(2) Why is it easier to hammer a sharp nail into wood than a blunt one?
Pressure = Force ÷ Area.
- A sharp nail has a smaller tip area, so the pressure for the same force is much greater,
- This greater pressure makes it easier to penetrate wood.
A blunt nail has a larger area at the tip, so the pressure is lower and it’s harder to hammer in.
6. Give two examples of situation to change the status of motion of an object by both push and pull.
OR
Why is it comfortable to lift a school bag with broad straps than thin straps
?
6. Answer:
Option 1 – Nose bleeding at high altitudes:
At high altitudes, air pressure is very low. The blood pressure inside the body becomes greater than the outside air pressure, which causes the thin blood vessels in the nose to burst, leading to nose bleeding.
OR
Option 2 – Hammering a nail:
It is easier to hammer a sharp nail into wood than a blunt one because a sharp nail has a smaller tip area, so the force is concentrated on a smaller area, producing greater pressure.
Greater pressure helps the nail to pierce the wood easily.
7. Why do we feel the effect of atmospheric pressure.
OR
How would pressure change if
1. area is doubled keeping force constant
2. force is doubled keeping area constant ?
7. Answer:
Option 1 – Effect of atmospheric pressure:
We feel the effect of atmospheric pressure because air exerts pressure in all directions, including on our body.
However, we do not get crushed because the pressure of air inside our body balances the external atmospheric pressure.
OR
Option 2 – Change in pressure:
-
If area is doubled keeping force constant,
→ Pressure becomes half.
(Because ) -
If force is doubled keeping area constant,
→ Pressure becomes double.
8. MATCH THE FOLLOWING
S.NO. DISEASE MICROORGANISMS
1 Pneumonia Virus
2 Coughs Bacteria
3 AIDS Virus
8. Here’s the correct matching:
| S.No. | Disease | Microorganism |
|---|---|---|
| 1 | Pneumonia | Bacteria |
| 2 | Coughs (Common cold) | Virus |
| 3 | AIDS | Virus |
9. Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic
substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
OR
Match the substances given in Column A with their uses given
in Column B. A B
(1) Copper (a) Acid
(2) Silver (b) Electric wire
(3) Cu(OH)2. (c) Jewellery
(4) HNO3. (d) Haemoglobin
(5) Sulphur. (e) Base
(6) Iron. (f) Non-metal
9.Answer:
Part A – Reasons:
(a) Aluminium foils are used to wrap food items:
→ Aluminium does not react with food and prevents spoilage, keeping food safe.
(b) Immersion rods for heating liquids are made up of metallic substances:
→ Metals are good conductors of heat, so they heat liquids efficiently.
(c) Copper cannot displace zinc from its salt solution:
→ Copper is less reactive than zinc, so it cannot replace zinc from zinc salt solution.
(d) Sodium and potassium are stored in kerosene:
→ Sodium and potassium react violently with air and water, so storing them in kerosene prevents contact with air and moisture.
Part B – Matching Column A with Column B:
| A (Substance) | B (Use) |
|---|---|
| 1. Copper | (b) Electric wire |
| 2. Silver | (c) Jewellery |
| 3. Cu(OH)₂ | (e) Base |
| 4. HNO₃ | (a) Acid |
| 5. Sulphur | (f) Non-metal |
| 6. Iron | (d) Haemoglobin |
10. In the following situations identify the agent exerting the force and the
object on which it acts. State the effect of the force in each case.
(a) Squeezing a piece of lemon between the fingers to extract its juice.
(b) Taking out paste from a toothpaste tube.
(c) A load suspended from a spring while its other end is on a hook
fixed to a wall.
10. Answer:
| Situation | Agent exerting force | Object on which force acts | Effect of the force |
|---|---|---|---|
| (a) Squeezing a piece of lemon between fingers | Fingers | Lemon | Juice comes out; lemon is compressed |
| (b) Taking out paste from a toothpaste tube | Hand | Toothpaste tube | Paste comes out; tube gets deformed |
| (c) Load suspended from a spring | Load (weight of object) | Spring | Spring stretches; shows elongation due to load |
11. Answer the following
(a) How many objects should be present for a force to come into play?
(b) Two friends A and B are applying a force of 2 newton and 4 newton
on a box in the same direction. What will be the total force applied
by them?
(c) Does the force of attraction also act on the objects moving in the air?
11. Answer:
(a) For a force to come into play, there must be at least two objects — one applying the force (agent) and the other on which the force acts (object).
(b) If two friends A and B apply 2 N and 4 N on a box in the same direction, the total force = 2 + 4 = 6 N.
(c) Yes, the force of attraction (like gravity) acts on objects moving in the air.
→ Example: A ball thrown in the air falls back due to the gravitational attraction of the Earth.
12. Microorganisms are useful in our lives in the following ways .Bacteria
cause the decay of dead plants and animals for cleaning the environment.
Nitrogen fixing bacteria convert the atmospheric nitrogen into nitrates.
Bacteria are used in the production of vinegar, curd, cheese, etc. Bacteria
are used in sewage disposal plants. Some other microorganisms like viruses,
fungi, yeast etc. are also used to produce valuable medical, agricultural and
industrial products, like antibiotics, alcohol in breweries, and also used in
baking industries.
1. The microbes which feed on dead and decaying organic matter for their
nutrition are called
(a) Autotrophs (b) Heterotrophs
(c) Parasites (d) Saprotrophs
Answer:
I. The microbes which feed on dead and decaying organic matter → (d) Saprotrophs
II The bacteria which convert the atmospheric nitrogen into nitrates i.e
nitrogen fixation is
(a) Lactobacillus (b) Rhizobium
(c) Anthrax (d) Mycobacterium
II. The bacteria which convert atmospheric nitrogen into nitrates (nitrogen fixation) → (b) Rhizobium
III The bacteria which is responsible for the production of curd and cheese
from the milk is
(a) Lactobacillus (b) Rhizobium
(c) Anthrax (d) Mycobacterium
III. The bacteria responsible for the production of curd and cheese from milk → (a) Lactobacillus
IV The microbes which are responsible for the process of fermentation in
breweries industries is
(a) Bacteria (b) Fungi
(c) Virus (d) Yeast.
IV. The microbes responsible for fermentation in breweries → (d) Yeast
13. environment and for the healthcare of human beings, plants and animals.
Microorganisms cause diseases in human beings, plants and animals.
Microorganisms spoil food and cause food poisoning. Microorganisms also
degrade the quality of the environment and surroundings. Thus there is also
a need for protection of our self and our environment from various harmful
organisms.
I The microorganisms which are responsible for causing the diseases are
called as
(a) Pathogen (b) Microbe
(c) Parasite (d) Bacteriophage
1. Here are the answers to your questions with brief explanations:
I. The microorganisms which are responsible for causing the diseases are called:
Answer: (a) Pathogen
Explanation: Pathogens are microbes that cause diseases in humans, animals, or plants.
IV. The microorganism which lives only inside a host:
Answer: (d) Virus
Explanation: Viruses are obligate parasites; they cannot survive or reproduce outside a host cell.
If you want, I can make a tiny diagram showing pathogens, viruses, bacteria, and diseases to remember this easily. Do you want me to do that?
II Which of the following is an infectious disease caused by microorganisms?
(a) AIDS (b) Polio
(c) Tuberculosis (d) Dengue
II. Which of the following is an infectious disease caused by microorganisms?
Answer: (c) Tuberculosis
Explanation: Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. AIDS is caused by a virus (HIV), Polio by a virus, Dengue by a virus. Since the question asks for infectious diseases caused by microorganisms in general, Tuberculosis is the correct choice among the options provided.
III Which one of the following diseases is caused by a Virus?
(a) Hepatitis (b) Anthrax
(c) Tuberculosis (d) Tetanus
III. Which one of the following diseases is caused by a Virus?
Answer: (a) Hepatitis
Explanation: Certain types of Hepatitis (like Hepatitis A, B, C, E) are caused by viruses. Anthrax is bacterial, Tuberculosis is bacterial, and Tetanus is bacterial.
IV The microorganisms which is living only when inside the host is
(a) Bacteria (b) Fungi
(c ) Protozoa (d) Virus
14. Some properties are listed in the following Table. Distinguish between
metals and non-metals on the basis of these properties.
Properties Metals Non-metals
1. Hardness
2. Malleability
3. Ductility
OR
Conduction of Heat
and electricity
1. Metals
Non-metals
2.Metals
Non-metals
3. Metals
Non-metals
OR
4.Metals
Non-metals
14. It looks like you want a comparison between metals and non-metals. Here’s a clear table:
| Property | Metals | Non-metals |
|---|---|---|
| Appearance | Shiny (lustrous) | Dull |
| Malleability | Malleable (can be hammered into sheets) | Brittle (breaks easily) |
| Ductility | Ductile (can be drawn into wires) | Non-ductile |
| Conductivity | Good conductor of heat and electricity | Poor conductor (insulators) |
| State at room temperature | Mostly solid (except mercury) | Solid, liquid, or gas |
| Density | Usually high | Usually low |
| Strength | Strong | Weak |
| Example | Iron, Copper, Aluminium | Sulphur, Oxygen, Carbon |
15 Metals and non-metals are very useful for us. Metals are used to make
cooking wares, In making electric appliances, electric wires, fridge etc,
Sheets of aluminium and iron for buildings materials, In manufacturing
jewelleries from gold, silver, coins from copper and aluminium etc. Non-
metals are useful for so many purposes like the preparation of ammonia,
nitric acid and fertilizers, for the purification of water, as a rocket fuel, to
make pencils, preparation of sulphuric acid.
1. The metal which is used to make electric wire is
(a) Gold (b) Copper
(c) Sodium (d) Mercury
Answer:
I. The metal which is used to make electric wire → (b) Copper
II The metals which are used to make jewellery are
(a) Gold and silver (b) Copper and iron
(c) Sodium and potassium (d) Lead and Zinc
II. The metals which are used to make jewellery → (a) Gold and Silver
3. The non-metals which are used to make fertilizers are
(a) Carbon and hydrogen (b) Nitrogen and phosphorous
(c) Chlorine and bromine (d) Sulphur and Oxygen.
III. The non-metals which are used to make fertilizers → (b) Nitrogen and Phosphorus
OR
The non-metal which is used for the purification of water is
(a) Bromine (b) Oxygen
(c) Chlorine (d) Hydrogen
OR The non-metal which is used for the purification of water → (c) Chlorine
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