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Class 8 Science Practice Test Online

Science isn't a list of dry definitions; it is the study of how things work! From the tiny engines inside our cells to the friction keeping your shoes on the ground, this practice area invites you to put your theories to the test. Let's solve numerical pressure questions, identify metals, and see how crops grow.

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About this Class 8 Science practice test

Why does a blunt object struggle to cut through what a sharp edge slices effortlessly? Class 8 Science is where we begin looking behind the scenes of physical, chemical, and organic worlds. This page provides a conceptual playground to help students identify the active laws of nature and stop struggling with tedious memorization.

Class 8 Science Practice Test sample questions

These starter questions help you launch a science mock test quickly. Swap them with your own worksheet, notebook, or textbook questions any time.

1. What is the SI unit of force?
2. Which force pulls every object toward the Earth?
3. Why does a sharp knife cut vegetables more easily than a blunt knife?
4. A car travels 120 km in 3 hours. Find its average speed.
5. What happens to friction when we apply oil between two moving machine parts?
6. Name the process by which a liquid changes into vapor from its surface at any temperature.
7. Which layer of atmosphere contains most weather changes like rain and storms?
8. Why does a ship made of iron float, while a small iron nail sinks in water?
9. Write one difference between conduction and convection.
10. What is the formula for pressure?
11. Which property allows metals to be drawn into thin wires?
12. Why is graphite, a form of non-metal carbon, used in electrical cells?
13. Name the process in which iron reacts with oxygen and moisture to form a reddish-brown layer.
14. Which gas is necessary for combustion?
15. Why is water not used to extinguish an electrical fire?
16. State one use of the alloy brass in daily life.
17. Which indicator turns pink in a basic solution: phenolphthalein or blue litmus?
18. Why are LPG and CNG called clean fuels compared to coal?
19. What is the pH value of a neutral solution at room temperature?
20. Name one method used to prevent rusting of iron tools.
21. Which cell organelle is known as the powerhouse of the cell?
22. What is the function of xylem tissue in plants?
23. Name the microorganism used in bread making.
24. Why do farmers add manure or fertilizers to soil before sowing seeds?
25. What is pasteurization?
26. Give one example of a food chain from a grassland ecosystem.
27. What do we call organisms that make their own food by photosynthesis?
28. Why should drinking water be boiled in areas with possible microbial contamination?
29. Name one harmful effect of excessive plastic waste on the environment.
30. What is the full form of PCR used in emergency medicine and disaster response?

Syllabus & Core Topics

Force, friction, pressure, and buoyancyMetals, non-metals, alloys, and corrosionCombustion types, fire safety, and fuelsCell organelles, microbes, and crop scienceEcosystems, food chains, and pollution management

Think of physics, chemistry, and biology as three chapters of the same story. Physics shows how energy moves, chemistry shows how matter reacts, and biology maps how life adapts. Looking at them as connected ideas helps you write richer, more intuitive answers on your science papers.

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Why this practice page is useful

Helping students move beyond memorizing terms to see how pressure, friction, and combustion operate in daily life builds practical reasoning.
Frequent practice with terms like xylem, displacement, and ductility improves answer precision in exams.
Guided numerical questions on speed and pressure train students to write clear, error-free working steps and calculations.

Answer key & quick explanations

Short answers for the sample questions above. Use this to self-check before generating a fresh AI-built mock test.

1. What is the SI unit of force?
newton (N)
The SI unit of force is the newton, written as N. One newton is the force needed to accelerate a 1 kg object by 1 m/s^2, so the relation is F = ma.
2. Which force pulls every object toward the Earth?
gravitational force
Gravitational force is the universal pull that attracts objects toward Earth's center. This is why a dropped ball falls downward and why we stay firmly on the ground instead of floating away.
3. Why does a sharp knife cut vegetables more easily than a blunt knife?
Because a sharp edge applies greater pressure on a smaller area.
Pressure depends on area for the same force: P = F/A. A sharp knife has a much smaller contact area, so pressure rises quickly and cutting becomes easier. A blunt edge spreads force over a larger area, reducing pressure.
4. A car travels 120 km in 3 hours. Find its average speed.
40 km/h
Average speed is total distance divided by total time. Using v = d/t, we get v = 120/3 = 40 km/h. A common student trap is multiplying instead of dividing when time is given.
5. What happens to friction when we apply oil between two moving machine parts?
Friction decreases.
Oil forms a thin lubricating layer between the surfaces. This layer prevents direct rough contact, so friction decreases and machine parts move smoothly with less heating and wear.
6. Name the process by which a liquid changes into vapor from its surface at any temperature.
evaporation
Evaporation is a surface process that can happen below the boiling point. Faster-moving surface particles escape into air as vapor, which is why wet clothes dry even on mildly warm days.
7. Which layer of atmosphere contains most weather changes like rain and storms?
troposphere
Most weather events occur in the troposphere because it holds most atmospheric water vapor and clouds. As altitude rises in this layer, temperature usually drops, helping cloud and storm formation.
8. Why does a ship made of iron float, while a small iron nail sinks in water?
A ship displaces a much larger volume of water and has lower average density than a nail.
Floating depends on buoyant force and average density, not only material type. A ship's hollow design makes its overall density lower than water, so upthrust balances weight. A compact nail displaces little water and sinks.
9. Write one difference between conduction and convection.
Conduction transfers heat without bulk movement of particles, while convection transfers heat by movement of fluid.
In conduction, neighboring particles pass energy through collisions, typically in solids. In convection, warmer fluid rises and cooler fluid sinks, creating currents that transfer heat in liquids and gases.
10. What is the formula for pressure?
Pressure = Force / Area
Pressure is calculated using P = F/A. This tells us that for the same force, reducing area increases pressure. Units follow as N/m^2, also called the pascal (Pa).
11. Which property allows metals to be drawn into thin wires?
ductility
Ductility is the property of a material that allows it to be stretched into wires without breaking. Copper and aluminum are common examples used in electrical wiring due to high ductility.
12. Why is graphite, a form of non-metal carbon, used in electrical cells?
Because graphite conducts electricity.
Most non-metals are poor conductors, but graphite is an important exception. Its layered structure has mobile electrons, allowing current flow, so it is used as an electrode in many dry cells.
13. Name the process in which iron reacts with oxygen and moisture to form a reddish-brown layer.
rusting
Rusting is corrosion of iron in the presence of oxygen and water, producing hydrated iron oxide. A simplified word equation is: Iron + Oxygen + Water -> Hydrated Iron Oxide.
14. Which gas is necessary for combustion?
oxygen
Combustion needs three conditions: fuel, oxygen, and heat to ignition temperature. Removing oxygen interrupts this fire triangle, which is why smothering can stop flames.
15. Why is water not used to extinguish an electrical fire?
Water can conduct electricity and may cause electric shock.
Ordinary water often contains dissolved ions, so it can conduct electricity. Throwing water on a live electrical source risks shock and may spread danger; dry sand or CO2 extinguishers are safer choices.
16. State one use of the alloy brass in daily life.
Brass is used in utensils, taps, and musical instruments.
Brass, an alloy of copper and zinc, resists corrosion better than many pure metals and has good workability. That is why it is commonly used in decorative fittings, taps, and instrument parts.
17. Which indicator turns pink in a basic solution: phenolphthalein or blue litmus?
phenolphthalein
Phenolphthalein is colorless in acidic solution and turns pink in basic solution. Blue litmus does not turn pink; instead, it generally remains blue in base and turns red in acid.
18. Why are LPG and CNG called clean fuels compared to coal?
They burn more completely and produce less smoke and harmful residues.
LPG and CNG have higher calorific efficiency and cleaner combustion profiles, releasing fewer particulates and less ash than coal. Cleaner burning means improved air quality and reduced soot deposition.
19. What is the pH value of a neutral solution at room temperature?
7
A neutral solution has an equal concentration of hydrogen and hydroxide ions. At room temperature this balance corresponds to pH 7, as seen in pure distilled water.
20. Name one method used to prevent rusting of iron tools.
painting, oiling, galvanization, or greasing (any one)
Rusting slows down when iron is protected from moisture and oxygen. Coatings like paint or oil create a barrier, while galvanization adds zinc that protects the iron surface from corrosion.
21. Which cell organelle is known as the powerhouse of the cell?
mitochondria
Mitochondria release usable energy by cellular respiration, producing ATP for cell activities. A useful memory cue is: powerhouse means power production, and mitochondria are the cell's energy stations.
22. What is the function of xylem tissue in plants?
It transports water and dissolved minerals from roots to other plant parts.
Xylem vessels act like upward pipelines. They carry water and minerals absorbed by roots toward stems and leaves, supporting photosynthesis and structural firmness in many plants.
23. Name the microorganism used in bread making.
yeast
Yeast ferments sugars and releases carbon dioxide gas. The trapped gas makes dough rise and become soft, creating the porous texture seen in bread after baking.
24. Why do farmers add manure or fertilizers to soil before sowing seeds?
To replenish nutrients and improve crop growth.
Repeated cropping reduces essential nutrients such as nitrogen, phosphorus, and potassium. Manure improves soil texture and water retention, while fertilizers quickly supply required nutrients for healthy growth.
25. What is pasteurization?
Heating milk or liquid food to a specific temperature and then cooling it quickly to kill harmful microbes.
Pasteurization reduces microbial load without major nutrient loss. In common school-level reference, milk is heated to about 70 degrees Celsius for around 15-30 seconds and then rapidly cooled.
26. Give one example of a food chain from a grassland ecosystem.
grass -> grasshopper -> frog -> snake -> eagle
A food chain shows transfer of food energy from producers to consumers in sequence. Here, grass is the producer, and each next organism feeds on the previous one.
27. What do we call organisms that make their own food by photosynthesis?
autotrophs (producers)
Autotrophs prepare food from carbon dioxide and water using sunlight and chlorophyll. They form the first trophic level and support almost every food web directly or indirectly.
28. Why should drinking water be boiled in areas with possible microbial contamination?
Boiling kills many disease-causing microorganisms.
Boiling raises water temperature high enough to inactivate many harmful bacteria, viruses, and protozoa. This lowers the risk of water-borne diseases such as cholera, typhoid, and dysentery.
29. Name one harmful effect of excessive plastic waste on the environment.
It pollutes soil and water and can harm animals that ingest it.
Plastic degrades very slowly, so it accumulates in land and water bodies. Animals may eat plastic pieces by mistake, leading to injury, poisoning, or death, and microplastics can enter food chains.
30. What is the full form of PCR used in emergency medicine and disaster response?
Police Control Room
In the context of emergency and disaster response, PCR stands for Police Control Room, the central unit (commonly reached via PCR vans) that coordinates rapid police response during emergencies.

Curriculum Mapping & Learning Guide

Use this breakdown to identify which skills each question tests and guide post-test review.

Physics Foundations (Questions 1-10)

Checks understanding of force, pressure, friction, why objects float or sink, and basic speed calculations.

Chemistry in Everyday Life (Questions 11-20)

Tests properties of metals, conditions needed for burning, rust prevention, and acid-base indicators.

Biology and Environment (Questions 21-30)

Measures core cell parts, crop sowing and harvesting steps, microorganisms, food chains, and pollution.

Class 8 Science chapters covered

Chapter 1: Measuring forces, pressures on different surface areas, and liquid pressure effects.
Chapter 2: Exploring friction resistance, machines lubrication, and simple speed calculations.
Chapter 3: Comparing metals and non-metals on electricity conductivity, rust, and alloys.
Chapter 4: Understanding fuel types, conditions needed for burning, and fire extinguisher use.
Chapter 5: Learning cell organelle roles, microbes, pasteurization, and fermentation.
Chapter 6: Studying soil preparation, sowing, and restoring soil nutrients in crop fields.
Chapter 7: Tracing food chains in grassland ecosystems and controlling environmental pollution.

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