Physical and Chemical Changes Quiz - ICSE Class 8 Science
Free practice quiz: Physical and Chemical Changes (ICSE Class 8 Science). 48 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Which of the following is an example of a physical change?
- Burning of wood
- Rusting of iron
- Melting of ice
- Digestion of food
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Answer: C. Melting of ice
A physical change alters the form or appearance of a substance but not its chemical composition. Melting of ice is a change of state from solid to liquid, where water molecules remain H2O. Burning wood, rusting of iron, and digestion of food involve the formation of new substances, hence they are chemical changes.
Which of the following is an example of a chemical reaction that produces heat (exothermic)?
- Melting of ice
- Dissolving sugar in water
- Burning of fuel
- Evaporation of water
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Answer: C. Burning of fuel
Burning of fuel, such as wood or natural gas, releases a significant amount of heat and light, indicating an exothermic chemical reaction. Melting, dissolving, and evaporation are typically processes that absorb heat (endothermic) or are neutral.
Which of the following processes releases energy (exothermic)?
- Melting of ice
- Photosynthesis
- Respiration
- Evaporation of water
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Answer: C. Respiration
Respiration is the process by which organisms break down glucose to release energy for their life processes. This is an exothermic chemical reaction. Photosynthesis absorbs energy. Melting and evaporation absorb energy.
When a candle burns, wax is consumed, producing light, heat, carbon dioxide, and water vapor. This is:
- A physical change
- A reversible physical change
- A chemical change
- A change of state only
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Answer: C. A chemical change
Burning of a candle is combustion, a chemical reaction where wax reacts with oxygen to form new substances like carbon dioxide and water vapor, releasing energy. This is an irreversible chemical change.
Which of the following is a characteristic of a chemical change?
- No new substance is formed.
- The change is usually reversible.
- Energy is absorbed or released.
- The physical state may change but chemical composition remains the same.
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Answer: C. Energy is absorbed or released.
A key characteristic of chemical changes is the absorption or release of energy (heat, light, etc.) as bonds are broken and formed. New substances are formed, and the changes are typically irreversible.