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Class 7 Science Chapter 5 Changes Around Us Physical and Chemical Solutions | Curiosity NCERT Answers 2026-27 | Amresh Academy

Amresh Academy April 17, 2026

 


 

🌟 Class 7 Science Curiosity – Chapter 5 Solutions

🔥 Changes Around Us: Physical and Chemical | Amresh Academy

📝 🔹 Let Us Enhance Our Learning

1. Which of the following statements are the characteristics of a physical change?

(i) The state of the substance may or may not change.
(ii) A substance with different properties is formed.
(iii) No new substance is formed.
(iv) The substance undergoes a chemical reaction.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (iii) and (iv)

👉 Answer: (c) (i) and (iii) ✅

👉 Explanation:
✔️ Physical change → only form/state changes
❌ No new substance is formed

2. Predict which of the following changes can be reversed and which cannot be reversed. If you are not sure, you may write that down. Why are you not sure about these?

(i) Stitching cloth to a shirt
(ii) Twisting of straight string
(iii) Making idlis from a batter
(iv) Dissolving sugar in water
(v) Drawing water from a well
(vi) Ripening of fruits
(vii) Boiling water in an open pan
(viii) Rolling up a mat
(ix) Grinding wheat grains to flour
(x) Forming of soil from rocks

👉 Answer:

(i) Cannot be reversed ❌
(ii) Can be reversed 🔄
(iii) Cannot be reversed ❌
(iv) Can be reversed 🔄
(v) Can be reversed 🔄
(vi) Cannot be reversed ❌
(vii) Can be reversed 🔄
(viii) Can be reversed 🔄
(ix) Cannot be reversed ❌
(x) Cannot be reversed ❌

3. State whether the following statements are True or False. In case a statement is False, write the correct statement.

(i) Melting of wax is necessary for burning a candle. (True/False)
(ii) Collecting water vapour by condensing involves a chemical change. (True/False)
(iii) The process of converting leaves into compost is a chemical change. (True/False)
(iv) Mixing baking soda with lemon juice is a chemical change. (True/False)

👉 Answer:

(i) True ✅
(ii) False ❌ → It is a physical change
(iii) True ✅
(iv) True ✅

4. Fill in the blanks in the following statements:

(i) Nalini observed that the handle of her cycle has got brown deposits. The brown deposits are due to ______ and this is a ______ change.
(ii) Folding a handkerchief is a ______ change and can be ______.
(iii) A chemical process in which a substance reacts with oxygen with evolution of heat is called ______ and this is a ______ change.
(iv) Magnesium, when burnt in air, produces a substance called ______. The substance formed is ______ in nature. Burning of magnesium is a ______ change.

👉 Answer:

(i) rusting, chemical
(ii) physical, reversed
(iii) combustion, chemical
(iv) magnesium oxide, basic, chemical

5. Are the changes of water to ice and water to steam, physical or chemical? Explain.

👉 Answer:
These are physical changes 🔄

👉 Explanation:
Only state changes (solid/liquid/gas)
✔️ Substance remains same → H₂O

6. Is curdling of milk a physical or chemical change? Justify your statement.

👉 Answer:
It is a chemical change 🧪

👉 New substance (curd) forms → irreversible

7. Natural factors, such as wind, rain, etc., help in the formation of soil from rocks. Is this change physical or chemical and why?

👉 Answer:
✔️ Both physical + chemical

👉 Physical → breaking rocks
👉 Chemical → reactions with air/water

8. Read the following story titled ‘Eco-friendly Prithvi’...

👉 Answer:

  • Cutting vegetables → physical change
  • Collecting waste → physical change
  • Decomposition → chemical change
  • Plant growth → chemical change

👉 Title: 🌱 “Waste to Wealth”

9. Some changes are given here... (Venn Diagram)

👉 Answer:

🔵 A (Physical):

  • Tearing paper
  • Melting ice
  • Folding clothes

🔴 B (Chemical):

  • Rusting
  • Curdling milk
  • Ripening fruits
  • Burning magnesium
  • Baking soda + vinegar

🟣 C (Both):

  • Burning candle 🕯️

10. The experiments shown in Fig. 5.11a, b, c and d were performed. Find out in which case(s) did lime water turn milky and why?

(a) Vinegar and baking soda
(b) Lemon juice and vinegar
(c) Vinegar and common salt
(d) Lemon juice and baking soda

👉 Answer: (a) and (d) ✅

👉 Reason:
Carbon dioxide gas is formed → turns lime water milky 🧪

✍️ 🔹 Very Short Answer Type Questions

What is a physical change?

👉 No new substance formed 🔄

What is a chemical change?

👉 New substance formed 🧪

Give one example of a reversible change.

👉 Melting ice ❄️

Which gas turns lime water milky?

👉 Carbon dioxide 💨

What is ignition temperature?

👉 Minimum temp to start burning 🔥

🧠 🔹 Short Answer Type Questions

How is a physical change different from a chemical change?

👉 Physical → no new substance
👉 Chemical → new substance formed

Why is rusting of iron considered a chemical change?

👉 Forms new substance (iron oxide) 🟤

What is combustion?

👉 Reaction with oxygen + heat 🔥

How does burning of a candle involve both physical and chemical changes?

👉 Melting → physical
👉 Burning → chemical

What is the role of oxygen in combustion?

👉 Supports burning 🌬️

📖 🔹 Descriptive Answer Type Questions

What are the three essential conditions for combustion?

👉 Fuel + Oxygen + Heat 🔥

Describe what happens when vinegar reacts with baking soda.

👉 Produces CO₂ gas → chemical change

Why is burning of magnesium a chemical change?

👉 New substance (MgO) formed

How do both physical and chemical changes occur in a burning candle?

👉 Wax melts + burns simultaneously

What is weathering of rocks?

👉 Breaking of rocks → soil formation 🌍

🚀 🔹 Exploring Questions

Why are some changes considered undesirable?

👉 Cause damage (rusting, spoilage)

Can chemical changes be prevented? Explain with an example.

👉 Yes → painting, oiling prevents rust

Why is burning paper using sunlight a chemical change?

👉 New substances (ash, gas) formed

Is curdling of milk a physical or chemical change? Justify.

👉 Chemical change 🧪

How does erosion represent a physical change?

👉 Only form changes, no new substance

 

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