Class 8 Science Important Questions with Answers

Class 8 Science Important Questions cover all 13 chapters of the new NCERT Curiosity textbook. The questions test observation, scientific reasoning, concepts, experiments and their use in daily life.

Class 8 Science introduces students to the way scientists ask questions, conduct investigations and use evidence. It combines ideas from Biology, Chemistry, Physics, environmental science and astronomy.

The Class 8 Science Important Questions below help students revise important concepts across the complete syllabus. Students should understand the reason behind every observation instead of memorising answers without context.

Key Takeaways

• The new Class 8 Science textbook contains 13 chapters.
• Chapter 1 introduces scientific investigation and fair testing.
• Biology chapters cover microorganisms, health and ecosystems.
• Physics chapters cover electricity, forces, pressure and light.
• Chemistry chapters explain particles, matter and solutions.
• Astronomy and Earth Science appear in the final chapters.
• Many questions require observation and reasoning.
• Diagrams should be neat and correctly labelled.
• Scientific answers should include evidence and explanation.

Class 8 Science Chapter-wise Important Questions

Important Class 8 Science Terms

Access Class 8 Science Important Questions in 30 Minutes

First 10 minutes: Revise investigation skills, microorganisms, health and electricity.

Next 10 minutes: Review force, pressure, particles, elements, compounds and solutions.

Final 10 minutes: Practise light, astronomy, ecosystems and Earth-related questions.

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Important Questions for Class 8 Science

Q1. What is a scientific investigation?

Answer:

A scientific investigation is a planned method used to answer a question through observation, experimentation and evidence.

It generally includes:

1. Asking a focused question
2. Forming a hypothesis
3. Planning a fair test
4. Collecting observations
5. Analysing results
6. Drawing a conclusion

The conclusion should be based on evidence collected during the investigation.

Q2. Why should only one variable be changed during a fair test?

Answer:

Only one variable should be changed so that its effect can be studied clearly.

Other conditions should remain the same. These are called controlled variables.

For example, while testing how sunlight affects plant growth, the plants should receive equal water and soil. Only the amount of sunlight should change.

Otherwise, it becomes difficult to identify the actual cause of the result.

Q3. What are microorganisms? Name their main groups.

Answer:

Microorganisms are living organisms that are too small to be seen clearly with the naked eye.

Their main groups include:

• Bacteria
• Fungi
• Protozoa
• Microscopic algae
• Viruses

Some microorganisms are useful in food production, decomposition and medicine. Others can cause disease.

Q4. How are microorganisms useful to humans?

Answer:

Microorganisms are useful in several ways.

• Bacteria help in making curd.
• Yeast is used in bread making.
• Some microorganisms produce antibiotics.
• Decomposers recycle nutrients in nature.
• Nitrogen-fixing bacteria improve soil fertility.
• Microorganisms are used in sewage treatment.

Their usefulness depends on the species and conditions in which they grow.

Q5. Why is a balanced diet important?

Answer:

A balanced diet supplies all essential nutrients in suitable amounts.

It should contain:

• Carbohydrates
• Proteins
• Fats
• Vitamins
• Minerals
• Fibre
• Water

Carbohydrates and fats provide energy. Proteins support growth and repair. Vitamins and minerals help the body function properly.

An unbalanced diet may cause weakness, poor growth or deficiency diseases.

Q6. How can communicable diseases be prevented?

Answer:

Communicable diseases can spread through air, water, food, direct contact or disease-carrying organisms.

They can be prevented by:

• Washing hands regularly
• Drinking clean water
• Keeping food covered
• Maintaining personal hygiene
• Taking recommended vaccines
• Avoiding close contact with infected persons
• Controlling mosquitoes and flies

Prevention interrupts the path through which disease-causing organisms spread.

Q7. What is the heating effect of electric current?

Answer:

When electric current passes through a conductor, electrical energy changes into heat energy.

This is called the heating effect of electric current.

It is used in:

• Electric irons
• Heaters
• Toasters
• Electric kettles
• Fuses

The amount of heat depends on the conductor, current and time for which the current flows.

Q8. How does an electric current produce a magnetic effect?

Answer:

A current-carrying wire produces a magnetic field around it.

This can be observed by placing a compass near the wire. The compass needle changes direction when current flows.

A coil carrying current acts like a magnet. Placing an iron core inside the coil forms an electromagnet.

Electromagnets are used in electric bells, cranes and relays.

Q9. What is force? Explain contact and non-contact forces.

Answer:

Force is a push or pull that can change an object’s motion, direction or shape.

Contact forces act only when objects touch.

Examples:

• Muscular force
• Frictional force

Non-contact forces act without direct contact.

Examples:

• Magnetic force
• Gravitational force
• Electrostatic force

A force may start, stop, speed up, slow down or deform an object.

Q10. Why does a sharp knife cut more easily than a blunt knife?

Answer:

Pressure depends on the force applied and the area over which it acts.

Pressure = Force/Area

A sharp knife has a very small edge area. The applied force therefore produces greater pressure.

A blunt knife has a larger contact area and produces less pressure for the same force.

This is why a sharp knife cuts more easily.

Q11. How are winds produced?

Answer:

Winds are produced because different parts of Earth heat unevenly.

Warm air becomes lighter and rises. This creates an area of lower pressure near the surface.

Cooler, denser air moves towards the low-pressure area.

This movement of air is called wind.

Differences in temperature and pressure therefore cause air to move.

Q12. How does a cyclone develop?

Answer:

A cyclone can develop over warm ocean water.

Warm, moist air rises and creates a low-pressure area. Surrounding air moves towards this region and also rises.

Water vapour condenses and releases heat. This supplies more energy to the system.

The moving air begins to rotate because of Earth’s rotation. The system can become a powerful storm with strong winds and heavy rain.

Q13. What evidence shows that matter is made of particles?

Answer:

Several observations show that matter is made of tiny particles.

• Sugar disappears when dissolved in water.
• The smell of perfume spreads through a room.
• Ink spreads slowly through water.
• Gases can be compressed.

These observations show that particles have spaces between them and remain in constant motion.

They also attract one another with different strengths.

Q14. Why do gases fill the entire container?

Answer:

Gas particles are far apart and move freely in all directions.

Their attractive forces are weak. They continuously collide with one another and with the walls of the container.

Therefore, they spread throughout the available space.

A gas has no fixed shape or volume and takes both from its container.

Q15. Differentiate between elements, compounds and mixtures.

Answer:

Q16. How can a mixture of iron filings and sand be separated?

Answer:

A magnet can separate iron filings from sand.

Iron is attracted to the magnet, while sand is not.

The magnet should be moved over the mixture. The iron filings stick to it and can be removed.

This method works because the components have different magnetic properties.

Q17. What is the difference between a solute and a solvent?

Answer:

A solute is the substance that gets dissolved.

A solvent is the substance that dissolves the solute.

For example, in a salt solution:

• Salt is the solute.
• Water is the solvent.

The final uniform mixture is called a solution.

The amount of solute that dissolves can depend on temperature and the nature of both substances.

Q18. What is a saturated solution?

Answer:

A saturated solution contains the maximum amount of solute that can dissolve at a particular temperature.

If more solute is added, it remains undissolved.

Heating may allow more solid solute to dissolve in many cases.

On cooling a hot saturated solution, some dissolved solute may separate as crystals.

Q19. Differentiate between reflection by a plane mirror and refraction through a lens.

Answer:

Reflection occurs when light strikes a surface and returns to the same medium.

A plane mirror forms a virtual, upright image of the same size.

Refraction occurs when light changes direction while passing from one transparent medium to another.

Lenses use refraction to form images.

A convex lens can converge light, while a concave lens spreads it.

Q20. Explain why Earth can support life.

Answer:

Earth supports life because it has several suitable conditions.

• Liquid water is available.
• The atmosphere contains useful gases.
• Temperatures allow water to remain liquid.
• Sunlight provides energy.
• Soil supports plant growth.
• The atmosphere protects life from harmful radiation.
• Natural cycles recycle water, carbon and nutrients.

Life depends on the interaction of land, water, air and living organisms.

How to Prepare Class 8 Science Important Questions

Begin by reading one chapter and identifying its main question, experiment and conclusion.

Prepare short tables for differences such as element and compound, solute and solvent, or reflection and refraction.

Draw diagrams for electric circuits, electromagnets, pressure, mirrors, lenses and natural cycles. Label each part clearly.

For activity-based questions, write the materials, method, observation and conclusion in the correct order.

Class 8 Science Preparation Tips

• Read the new NCERT chapter names carefully.
• Connect every concept with a daily-life example.
• Learn the reason behind each observation.
• Practise diagrams with correct labels.
• Use scientific terms in answers.
• Keep long answers organised with headings.
• Revise experiments through observation and conclusion.
• Avoid mixing questions from the old syllabus.
• Review all 13 chapters before examinations.

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