Welcome to Bodhiclasses – your trusted platform for simplified learning, deeper understanding, and exam-oriented content. At Bodhiclasses, we empower students with thoughtfully curated resources that strengthen concepts and build confidence. Today’s post brings you a full set of extra questions and answers from Chapter 5 – Changes Around Us, as per the NCERT Class 7 Science textbook.
10 Multiple Choice Questions (MCQs) – Changes Around Us
Q1. Which of the following is a physical change?
A. Rusting of iron
B. Melting of ice
C. Curdling of milk
D. Burning of paper
Ans: B. Melting of ice
Q2. The process of burning in the presence of oxygen is called:
A. Decomposition
B. Combustion
C. Condensation
D. Erosion
Ans: B. Combustion
Q3. Which of the following changes can be reversed?
A. Making curd from milk
B. Burning of wood
C. Folding of clothes
D. Cutting vegetables
Ans: C. Folding of clothes
Q4. What is formed when vinegar and baking soda react?
A. Oxygen
B. Hydrogen
C. Nitrogen
D. Carbon dioxide
Ans: D. Carbon dioxide
Q5. Which of these is NOT a requirement for combustion?
A. Oxygen
B. Fuel
C. Light
D. Heat
Ans: C. Light
Q6. Which of the following is a chemical change?
A. Boiling water
B. Melting wax
C. Burning of magnesium ribbon
D. Folding a paper
Ans: C. Burning of magnesium ribbon
Q7. The component of air that supports combustion is:
A. Nitrogen
B. Carbon dioxide
C. Oxygen
D. Hydrogen
Ans: C. Oxygen
Q8. The rust formed on iron is chemically known as:
A. Iron sulfate
B. Iron carbonate
C. Iron oxide
D. Iron nitrate
Ans: C. Iron oxide
Q9. Lime water turns milky when exposed to:
A. Oxygen
B. Hydrogen
C. Carbon dioxide
D. Water vapour
Ans: C. Carbon dioxide
Q10. Which of these is both a physical and a chemical change?
A. Cutting an apple
B. Burning a candle
C. Making dough
D. Dissolving salt
Ans: B. Burning a candle
10 One-Mark Questions (Very Short Answer) – Changes Around Us
Q1. What is a physical change?
Ans: A change in which no new substance is formed.
Q2. Give an example of a chemical change.
Ans: Burning of wood.
Q3. What gas turns lime water milky?
Ans: Carbon dioxide.
Q4. Name one combustible substance.
Ans: Kerosene.
Q5. What is rust chemically?
Ans: Iron oxide.
Q6. Define combustion.
Ans: A process where a substance reacts with oxygen and produces heat and/or light.
Q7. Can boiling of water be reversed?
Ans: Yes.
Q8. Is melting of wax a physical or chemical change?
Ans: Physical change.
Q9. What is the minimum temperature needed for a substance to catch fire?
Ans: Ignition temperature.
Q10. Which insect produces light due to a chemical change?
Ans: Firefly.
10 Two-Mark Questions (Short Answer) – Changes Around Us
Q1. Differentiate between physical and chemical changes.
Ans: Physical changes do not form new substances and are often reversible. Chemical changes form new substances and are mostly irreversible.
Q2. Explain why rusting is a chemical change.
Ans: Rusting involves a reaction between iron, water, and oxygen, forming a new substance called iron oxide.
Q3. Why does a candle stop burning when covered with a glass jar?
Ans: Due to lack of oxygen, which is essential for combustion.
Q4. Is burning of magnesium ribbon a chemical change? Why?
Ans: Yes, it forms a new substance (magnesium oxide) and releases heat and light.
Q5. State one similarity and one difference between boiling and condensation.
Ans: Both involve change in state. Boiling is vaporisation; condensation is gas turning into liquid.
Q6. What is weathering? Mention any one cause.
Ans: Weathering is the breaking down of rocks by physical or chemical forces, such as wind or rain.
Q7. Mention any two desirable changes and two undesirable changes.
Ans: Desirable: Cooking food, composting. Undesirable: Rusting, food spoilage.
Q8. Why is mixing vinegar and baking soda a chemical change?
Ans: It forms carbon dioxide gas and new substances.
Q9. How does erosion differ from weathering?
Ans: Erosion is the movement of weathered materials by wind or water, while weathering is the breakdown of rocks.
Q10. Give two examples where physical and chemical changes occur together.
Ans: Burning a candle, cooking food.
5 Higher Order Thinking Skills (HOTS)
Q1. Ramesh kept wet clothes under the sun and noticed a white residue on them. What could have caused this?
Ans: Water evaporated (physical change), leaving behind detergent salts.
Q2. A banana turned brown and soft over days. Explain the type of change and what causes it.
Ans: Chemical change due to enzymatic reactions and microbial activity.
Q3. Why does a fire go out when we blow over it gently, but grow stronger when we blow more forcefully?
Ans: Gentle blowing may reduce heat below ignition temp. Forceful blowing increases oxygen supply, enhancing combustion.
Q4. Can we call the melting of metal a chemical change? Justify.
Ans: No, melting metal is a physical change; its chemical composition remains the same.
Q5. Paper does not catch fire on its own in open air. But it burns with a matchstick. Explain.
Ans: The paper needs heat to reach its ignition temperature, which is provided by the matchstick.
