ACADIFY · FREE SCIENCE CHALLENGE

Class 8
Science.

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🔬 10 Questions ⏱️ About 20 Minutes 🧠 Conceptual Challenge

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1. An iron nail is placed in blue copper sulphate solution. After some time, a reddish-brown coating appears on the nail and the solution turns green. Which explanation is correct? A. Copper displaces iron from the solution because copper is more reactive. B. Iron displaces copper from the solution because iron is more reactive. C. Iron and copper sulphate undergo only a physical change, with no new substance formed. D. The green colour appears because the iron nail dissolves completely into water.

2. A student pushes a heavy box, but it does not move. Which statement best explains the situation? A. No force is acting on the box. B. The box has no inertia because it is stationary. C. The student's push is balanced by opposing forces, so the net force is zero. D. Friction always acts in the direction of motion, preventing the box from moving.

3. A plant is kept in darkness for two days. A leaf is then partly covered with opaque paper and the plant is placed in sunlight. After a few hours, the leaf is tested for starch. Which result is expected? A. Both covered and uncovered parts turn blue-black. B. Only the uncovered part turns blue-black. C. Only the covered part turns blue-black. D. Neither part can turn blue-black because plants cannot store food as starch.

4. A candle is burning inside a closed glass jar. After some time, the flame goes out. What is the most accurate explanation? A. All the air inside the jar disappears. B. The wax instantly becomes non-combustible. C. The oxygen available for combustion falls below the level needed to sustain the flame. D. Carbon dioxide makes the wax freeze immediately.

5. Two bricks of equal weight are placed on soft soil. Brick P rests on its broad face, while Brick Q rests on its narrow face. Which statement is correct? A. Brick P exerts greater pressure because its area of contact is larger. B. Brick Q exerts greater pressure because its area of contact is smaller. C. Both bricks exert equal pressure because their weights are equal. D. Neither brick exerts pressure unless it moves.

6. An astronaut on the Moon strikes a metal object. Another astronaut standing some distance away cannot hear the sound directly through the surrounding vacuum. Why? A. Sound travels only through liquids. B. The Moon's gravity completely stops sound vibrations. C. Sound needs a material medium to travel, and a vacuum has no material medium. D. Metal objects cannot produce sound in space.

7. A student stores freshly cooked food in a refrigerator instead of leaving it at room temperature. Why does refrigeration generally slow food spoilage? A. Low temperature kills every microorganism immediately. B. Low temperature generally slows the growth and activity of many microorganisms. C. Refrigeration removes all water from the food. D. Microorganisms cannot survive in any food kept below room temperature.

8. A student stands 3 metres in front of a plane mirror. The student then walks 1 metre towards it. How far apart are the student and their image now? A. 2 metres B. 3 metres C. 4 metres D. 6 metres

9. A bicycle travels along a road. If friction between its tyres and the road becomes extremely small, which problem is most likely to occur? A. The bicycle becomes heavier. B. The bicycle becomes unable to experience gravity. C. The tyres may lose grip, making it difficult to start, turn, or stop safely. D. The bicycle automatically accelerates without any applied force.

10. A student connects two identical bulbs in series to a battery. One bulb breaks, creating an open circuit. What happens to the other bulb? A. It glows brighter because the broken bulb releases more electricity. B. It continues glowing at the same brightness. C. It stops glowing because the circuit is incomplete and current cannot flow through the series circuit. D. It glows only when the battery is disconnected.

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Class 8 Science.

Challenge your scientific thinking.

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Turn curiosity into knowledge.

Class 8
Science.

Turn curiosity
into knowledge.