---
title: "NCERT Solutions Class 7 Science Changes Around Us: Physical and Chemical"
url: https://www.swavid.com/science/class/7/chapter/changes-around-us-physical-and-chemical/ncert-solutions
dateModified: 2026-10-07T16:05:59+00:00
---

# NCERT Solutions Class 7 Science Changes Around Us: Physical and Chemical

This chapter's questions cover concepts related to physical and chemical changes, including the characteristics of each, their reversibility, and common examples like rusting, combustion, and weathering.

Free PDF (8 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-7/swavid-ncert-solutions-class-7-science-chapter-5-changes-around-us-physical-and-chemical-e04bd597a3.pdf

## Let Us Enhance Our Learning

### Question 1

*1 mark · MCQ*

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.

- (i) and (ii)
- (ii) and (iii)
- (i) and (iii)
- (iii) and (iv)

**Solution**

1. In a physical change, no new substance is formed and only physical properties like shape, size, or state change.
2. Statement (i) is correct as state may or may not change, and statement (iii) is correct as no new substance is formed.

**Answer:** (c) (i) and (iii)

> Common mistake: Students often confuse physical changes with chemical changes and choose options that mention the formation of new substances.

### Question 2

*3 marks · Short answer*

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

**Part (i)**

1. Stitching cloth to a shirt alters the shape and size by cutting and stitching.
2. This cannot be easily reversed to get back the original fabric piece.

Answer (i): Cannot be reversed

**Part (ii)**

1. Twisting a straight string changes its shape.
2. Unwinding it brings back the straight string, so it can be reversed.

Answer (ii): Can be reversed

**Part (iii)**

1. Making idlis from a batter involves cooking and chemical changes.
2. The original batter cannot be recovered.

Answer (iii): Cannot be reversed

**Part (iv)**

1. Dissolving sugar in water forms a solution.
2. Sugar can be recovered back by evaporation, so it is reversible.

Answer (iv): Can be reversed

**Part (v)**

1. Drawing water from a well is a physical process of moving water.
2. The water's state does not permanently change in a way that prevents reversal.

Answer (v): Can be reversed

**Part (vi)**

1. Ripening of fruits involves chemical changes in taste, color, and smell.
2. Ripe fruits cannot become raw again.

Answer (vi): Cannot be reversed

**Part (vii)**

1. Boiling water changes liquid water to water vapor.
2. The vapor can be condensed back into liquid water.

Answer (vii): Can be reversed

**Part (viii)**

1. Rolling up a mat changes its physical arrangement.
2. Unrolling the mat brings back the original form.

Answer (viii): Can be reversed

**Part (ix)**

1. Grinding wheat grains into flour changes the size of the grains permanently.
2. Flour cannot be joined back to form original grains.

Answer (ix): Cannot be reversed

**Part (x)**

1. Forming soil from rocks takes thousands of years through weathering.
2. Soil cannot be turned back into original solid rocks.

Answer (x): Cannot be reversed

**Answer:** Reversible changes: (ii), (iv), (v), (vii), (viii). Irreversible changes: (i), (iii), (vi), (ix), (x).

> Common mistake: Assuming dissolving sugar is irreversible because the solid sugar disappears temporarily.

### Question 3

*1 mark · True or false*

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)

**Part (i)**

1. Melting of wax is a physical change, whereas it is the vapour of wax that burns to produce a flame.
2. Therefore, the statement is False.

Answer (i): False. Melting of wax is not necessary for burning a candle; it is the vapour of wax which burns to produce a flame.

**Part (ii)**

1. Condensation of water vapour involves only a change of state from gas to liquid without forming any new substance.
2. Therefore, it is a physical change and the statement is False.

Answer (ii): False. Collecting water vapour by condensing involves a physical change.

**Part (iii)**

1. Conversion of leaves into compost forms new substances through decomposition.
2. Therefore, the statement is True.

Answer (iii): True

**Part (iv)**

1. Mixing baking soda with lemon juice produces carbon dioxide gas and new substances.
2. Therefore, the statement is True.

Answer (iv): True

**Answer:** Statements (i) and (ii) are False, while statements (iii) and (iv) are True.

> Common mistake: Confusing the melting of wax with the burning of wax vapours.

### Question 4

*1 mark · Fill in the blank*

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.

**Part (i)**

1. Brown deposits on an iron cycle handle are formed due to rusting.
2. Rusting involves the formation of a new substance, making it a chemical change.

Answer (i): rust, chemical

**Part (ii)**

1. Folding a handkerchief changes only its appearance without forming a new substance.
2. This change can be undone to get back the original handkerchief.

Answer (ii): physical, reversed

**Part (iii)**

1. A reaction with oxygen that releases heat is termed combustion.
2. Combustion always produces new substances and is a chemical change.

Answer (iii): combustion, chemical

**Part (iv)**

1. Burning magnesium in air produces magnesium oxide, which forms a basic solution in water.
2. The burning of magnesium is a chemical change.

Answer (iv): magnesium oxide, basic, chemical

**Answer:** Completed statements with appropriate textbook terms.

> Common mistake: Writing physical instead of chemical for burning and rusting reactions.

### Question 5

*3 marks · Short answer*

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

**Solution**

1. Water changing to ice is freezing, and water changing to steam is vaporization.
2. In both processes, only the physical state of water changes from liquid to solid or gas.
3. No new chemical substance is formed, hence both are physical changes.

**Answer:** Both changes of water to ice and water to steam are physical changes because no new substances are formed and the changes can be reversed.

> Common mistake: Thinking that change of state involves a chemical change because the appearance or form looks completely different.

### Question 6

*3 marks · Short answer*

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

**Solution**

1. Curdling of milk changes liquid milk into curd, which has a distinct sour taste and different properties.
2. A new substance is formed during this process, and it cannot be turned back into milk.
3. Therefore, curdling of milk is a chemical change.

**Answer:** Curdling of milk is a chemical change because a new substance with different properties is formed and the change cannot be reversed.

> Common mistake: Considering curdling as a physical change because it originates from milk.

### Question 7

*3 marks · Short answer*

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

**Solution**

1. The formation of soil from rocks involves both physical and chemical changes.
2. Physical changes occur when large rocks are broken down into smaller pieces by temperature changes, growing tree roots, or freezing water.
3. Chemical changes occur when water or chemicals in water react with the minerals in rocks, such as iron in basalt reacting to form iron oxide.

**Answer:** It involves both physical and chemical changes due to the breaking down of rocks and chemical reactions with water and air.

> Common mistake: Only mentioning physical weathering while forgetting that chemical reactions also occur between rock minerals and water or air.

### Question 8

*3 marks · Short answer*

Read the following story titled 'Eco-friendly Prithvi', and tick the most appropriate option(s) given in the brackets. Provide a suitable title of your choice for the story.
Prithvi is preparing a meal in the kitchen. He chops vegetables, peels potatoes, and cuts fruits (physical changes/chemical changes). He collects the seeds, fruits, and vegetable peels into a clay pot (physical change/chemical change). The fruits, vegetable peels, and other materials begin to decompose due to the action of bacteria and fungi, forming compost (physical change/chemical change). He decides to plant seeds in the compost and water them regularly. After a few days, he notices that the seeds begin to germinate and small plants start to grow, eventually blooming into colourful flowers (physical change/chemical change). His efforts are appreciated by all his family members.

**Solution**

1. Title: Prithvi, the Green Caretaker
2. Chopping vegetables, peeling potatoes, and cutting fruits are physical changes.
3. Decomposition of fruit and vegetable peels into compost and the germination of seeds into growing plants are chemical changes.

**Answer:** Title: Prithvi, the Green Caretaker. Cutting is a physical change, while decomposition and plant growth are chemical changes.

> Common mistake: Confusing decomposition and plant growth with physical changes.

### Question 9

*3 marks · Short answer*

Some changes are given here. Write physical changes in the area marked 'A' and chemical changes in the area marked 'B'. Enter the changes which are both physical and chemical in the area marked 'C'.
Process of burning a candle; Tearing of paper; Rusting; Curdling of milk; Ripening of fruits; Melting of ice; Folding of clothes; Burning of magnesium and Mixing baking soda with vinegar.

**Solution**

1. Area A (Physical changes): Tearing of paper, melting of ice, folding of clothes.
2. Area B (Chemical changes): Rusting, curdling of milk, ripening of fruits, burning of magnesium, mixing baking soda with vinegar.
3. Area C (Both physical and chemical): Process of burning a candle.

**Answer:** Physical changes: Tearing of paper, melting of ice, folding of clothes. Chemical changes: Rusting, curdling of milk, ripening of fruits, burning of magnesium, mixing baking soda with vinegar. Both: Burning of a candle.

> Common mistake: Forgetting that burning a candle involves both the physical change of melting wax and the chemical change of burning wax vapour.

### Question 10

*3 marks · Short answer*

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?

**Solution**

1. Lime water turns milky in cases (a) and (d).
2. In case (a), mixing vinegar and baking soda produces carbon dioxide gas, which turns lime water milky.
3. In case (d), mixing lemon juice (which contains acid like vinegar) and baking soda also produces carbon dioxide gas, which turns lime water milky.

**Answer:** Lime water turns milky in cases (a) and (d) because the reaction between an acid and baking soda produces carbon dioxide gas.

> Common mistake: Failing to recognize that lemon juice acts similarly to vinegar when mixed with baking soda to release carbon dioxide.

## Frequently asked questions

### How many questions are there in NCERT Solutions for Class 7 Science Chapter 5 Changes Around Us Physical and Chemical?

The Let Us Enhance Our Learning section has 10 questions. You can find step-by-step solutions for all of them in the free PDF available on this SwaVid page.

### Which topics are covered in the exercise questions of this chapter for the 2026-27 session?

The questions cover important concepts like characteristics of physical changes, classification of physical and chemical changes, curdling of milk as a chemical change, and the test for carbon dioxide using lime water. SwaVid provides detailed answers based on the new NCERT book for the 2026-27 session on this page.

### What is the hardest question type in this chapter and how should I approach it?

Questions involving the classification of daily life events into physical and chemical changes can be challenging. To approach them, you should first check if a new substance is formed, which is the main criterion explained in the SwaVid solutions on this page.

### How can I write answers to score full marks in Class 7 Science Chapter 5?

To score full marks, you should use scientific terms like reversible, irreversible, physical change, and chemical change in your answers. The free PDF on this SwaVid page shows you the exact structuring needed for top scores.

### Is the free PDF for Class 7 Science Chapter 5 Changes Around Us available on SwaVid?

Yes, the complete free PDF containing accurate answers for the new NCERT book aligned with the 2026-27 session is available right on this SwaVid page. You can easily view or download it to prepare for your exams.

## Related pages

- [Class 7 Science chapters](https://www.swavid.com/science/class/7)

Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student