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NCERT Solutions for Class 7 Science Chapter 5 Physical and Chemical Changes

NCERT Solutions for Class 7 Science Chapter 5 Physical and Chemical Changes

Edited By Shivani Poonia | Updated on Apr 29, 2025 02:07 PM IST

In our everyday lives, we often see various types of changes occurring. Some changes are permanent and irreversible, while others are temporary and reversible. The NCERT Chapter 5 Science class 7 has a detailed discussion on the two main types of changes, chemical changes (which involve a transformation where new substances are formed). For example, rusting of iron and physical changes (the substance's state changes, but its chemical composition remains the same), melting of ice into water, etc. This chapter also includes how to identify these changes and understand the processes and how these changes are essential to many man-made and natural processes.

This Story also Contains
  1. Free download physical and chemical changes class 7 solutions PDF for CBSE exam.
  2. Download PDF
  3. NCERT Solutions for Class 7 Science Chapter 5 Physical And Chemical Changes: Exercise Solutions
  4. Chapterwise NCERT Solutions of Class 7 Science
  5. Physical And Chemical Changes Class 7 Chapter 5-Topics
  6. Important terms to be remembered :
  7. Key Features of Class 7: Physical and Chemical Changes
  8. Practice Questions on Physical and Chemical Changes

These NCERT solutions are designed by our subject matter experts to offer a structured and systematic approach to these important concepts and help students develop a clear understanding of complex problems through a series of solved examples, questions, and conceptual explanations. These solutions also add extra value to the resources of the students to enhance their performance in board exams as well as in competitive exams. Our subject experts ensure that through the content provided below, students can gain maximum knowledge of the chapter.

**As per the CBSE Syllabus 2025-26, this chapter has been renumbered as Chapter 5 in Class 7 Science.

Free download physical and chemical changes class 7 solutions PDF for CBSE exam.

Download PDF

NCERT Solutions for Class 7 Science Chapter 5 Physical And Chemical Changes: Exercise Solutions

1. Classify the changes involved in the following processes as physical or chemical changes:

(a) Photosynthesis

Answer:

(a) Photosynthesis is a chemical change.

1. Classify the changes involved in the following processes as physical or chemical changes:

(b) Dissolving sugar in water

Answer:

(b) Dissolving sugar in water is a physical change.

1. Classify the changes involved in the following processes as physical or chemical changes:

(c) Burning of coal

Answer:

(c) Burning of coal is a chemical change.

1. Classify the changes involved in the following processes as physical or chemical changes:

(d) Melting of wax

Answer:

(d) Melting of wax is a physical change.

1. Classify the changes involved in the following processes as physical or chemical changes:

(e) Beating aluminium to make aluminium foil

Answer:

(e) Beating aluminium to make aluminium foil is a physical change.

1. Classify the changes involved in the following processes as physical or chemical changes:

(f ) Digestion of food

Answer:

Digestion of food is a chemical change.

During digestion, enzymes in the stomach and intestines break down food molecules into simpler molecules.

2. State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.

(a) Cutting a log of wood into pieces is a chemical change. (True/False)

(b) Formation of manure from leaves is a physical change. (True/False)

(c) Iron pipes coated with zinc do not rust easily. (True/False)

(d) Iron and rust are the same substances. (True/False)

(e) Condensation of steam is not a chemical change. (True/False)

Answer:

(a) False because cutting a log of wood into pieces is a physical change.

(b) False because the formation of manure from leaves is a chemical change.

(c) True.

(d) False because Iron and rust are different substances.

(e) True

3. Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.

(b) The chemical name of baking soda is _________.

(c) Two methods by which rusting of iron can be prevented are _________ and _________.

(d) Changes in which only _________ properties of a substance change are called physical changes.

(e) Changes in which new substances are formed are called _________ changes.

Answer:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of calcium carbonate.

(b) The chemical name of baking soda is sodium hydrogen carbonate.

(c) Two methods by which rusting of iron can be prevented are galvanization and painting.

(d) Changes in which only physical properties of a substance change are called physical changes.

(e) Changes in which new substances are formed are called chemical changes.

4. When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Answer:

When baking soda is mixed with lemon juice then it is a chemical change, bubbles are formed with the evolution of a carbon dioxide gas.

5. When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.

Answer:

When a candle burns, both physical and chemical changes take place. On heating, candle wax gets melted is a physical change since it again turns into wax on cooling.

The wax gives carbon dioxide, heat, light, water vapour and carbon soot on heating with a state chemical change.

Another example is the lighting of the bulb using a dry cell.

6. How would you show that setting of curd is a chemical change?

Answer:

The setting of curd is a chemical change because the new substance(curd) formed from milk differs in taste and it cannot be converted into milk again i.e. it is irreversible.

7. Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.

Answer:

The burning of wood is a chemical change because wood, after burning, gives carbon dioxide, ash, heat,and water vapour It is also an irreversible process.

Whereas cutting wood into small pieces is a physical change because the original composition of wood remains the same and no new substance is formed.

8. Describe how crystals of copper sulphate are prepared.

Answer:

The crystals of copper sulphate are prepared as follows:

1. A cup of water is taken in a beaker.

2. Add some drops of dilute sulphuric acid in it.

3. Heat it and when it starts boiling, add copper sulphate powder slowly with continuous stirring.

4. The copper sulphate powder is added till the saturation level.

5. Filter the solution and cool it.

6. Leave it undisturbed, and we will observe copper sulphate crystals after some hours.

9. Explain how painting of an iron gate prevents it from rusting.

Answer:

Painting of an iron gate prevents direct contact of iron with water and air(oxygen) which are required for rusting.

No exposure to water and oxygen with iron prevents iron from rusting.

10. Explain why rusting of iron objects is faster in coastal areas than in deserts.

Answer:

Rusting occurs with direct contact of iron with water and oxygen.

In coastal areas, the moisture content is high in the air, which means rusting of iron objects is faster in coastal areas because in deserts, moisture in the air is absent.

11. The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.

(ii) Process B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.

Answer:

The gas we use in the kitchen is called liquefied petroleum gas (LPG). In the cylinder, it exists as a liquid. When it comes out from the cylinder it becomes a gas (Change – A) then it burns (Change – B). This is a chemical change.

Thus, option (ii) is correct.

12. Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.

(ii) Process B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.

Answer:

Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B).

Both processes A and B are chemical change.

Thus, option (iii) is correct.

Class 7 science chapter 5 question answer holds substantial importance in a student's science education. These solutions provide a foundational understanding of the distinctions between physical and chemical changes in matter, which is fundamental in chemistry. Furthermore, the practical relevance of these concepts in daily life, coupled with their significance as a prerequisite for advanced chemistry studies, makes this chapter essential. It also fosters problem-solving skills and prepares students for examinations, making it a crucial component of their science curriculum. In terms of difficulty, the chapter's concepts are explained comprehensively in this article, making it accessible and enabling students to grasp the content effectively.

Chapterwise NCERT Solutions of Class 7 Science

The chapterwise solutions are given below:

NCERT Solutions for Class 7 Science Chapter 1 Nutrition in Plants

NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals

NCERT Solutions for Class 7 Science Chapter 3 Heat

NCERT Solutions for Class 7 Science Chapter 4 Acids, Bases and Salts

NCERT Solutions for Class 7 Science Chapter 5 Physical and Chemical Changes

NCERT Solutions for Class 7 Science Chapter 6 Respiration in Organisms

NCERT Solutions for Class 7 Science Chapter 7 Transportation in Animals and Plants

NCERT Solutions for Class 7 Science Chapter 8 Reproduction in Plants

NCERT Solutions for Class 7 Science Chapter 9 Motion and Time

NCERT Solutions for Class 7 Science Chapter 10 Electric Current and Its Effects

NCERT Solutions for Class 7 Science Chapter 11 Light

NCERT Solutions for Class 7 Science Chapter 12 Forests: Our Lifeline

NCERT Solutions for Class 7 Science Chapter 13 Wastewater Story

Physical And Chemical Changes Class 7 Chapter 5-Topics

  • Physical Changes
  • Chemical Change
  • Rusting Of Iron
  • Crystallisation

NCERT Solutions for Class 7 Subject Wise

NCERT Solutions for Class 7 Maths
NCERT Solutions for Class 7 Science

Important terms to be remembered :

The main terms to be memorised after going through the chapter and also the NCERT solutions are listed below.

  • Crystallisation: The process of forming large crystals of pure substances is known as crystallisation.
  • Rusting of iron: If iron is kept in moist air, a brownish film is formed on the iron. The brownish substance is called rust, and the process is called rusting.
  • Galvanisation: In the NCERT Class 7 book, the given definition is- Galvanisation is the process of depositing a layer of zinc on iron. Galvanisation prevents iron from rusting.

Key Features of Class 7: Physical and Chemical Changes

Clear Explanations- These solutions will provide you clear and concise explanations that will make the complex concepts easy to grasp for students.

Illustrations and Examples- The NCERT solutions include illustrations and examples to aid in visualization and better comprehension of concepts.

Relevance- The Class 7 physical and chemical changes NCERT solutions highlight the practical relevance of physical and chemical changes in daily life that will create a deeper connection to the subject matter.

Language Clarity- The language used in the solutions is student-friendly so that the students can follow along and learn independently.

Accessible- The question answers are readily available in printed and digital formats that will make them easily accessible to all students.

These features collectively make Class 7 NCERT solutions for "Physical and Chemical Changes" an invaluable resource for students to master the chapter effectively.

Practice Questions on Physical and Chemical Changes

Q1. What is a physical change? Give two examples.
Answer:
A physical change is a change in which no new substance is formed and the change is usually reversible.
Examples- Melting of ice, tearing of paper.

Q2. What is a chemical change? Give two examples.
Answer:
A chemical change is a change in which a new substance is formed and the change is usually irreversible.
Examples- Rusting of iron, burning of wood.

Q3. Is dissolving sugar in water a physical or chemical change? Why?
Answer:
It is a physical change because no new substance is formed, and the sugar can be recovered by evaporating the water.

Q4. Why is rusting of iron considered a chemical change?
Answer:
Rusting is a chemical change because a new substance (iron oxide) is formed, and the process is not easily reversible.

Q5. What are the signs that a chemical change has taken place?
Answer:

  • Common signs include:
  • Change in colour
  • Production of gas or bubbles
  • Formation of a new substance
  • Release or absorption of heat or light

Also, check the NCERT Books and the NCERT Syllabus here

Frequently Asked Questions (FAQs)

1. Is baking a cake a physical or chemical change?

Baking a cake involves both physical and chemical changes. It's primarily a chemical change. When heated, the ingredients undergo chemical reactions, forming new compounds that give the cake its texture and flavor. However, there are also physical changes, like the mixing of ingredients.

2. What are the key differences between chemical and physical changes?

Chemical Change: Difficult or impossible to reverse, Production of a gas (bubbles, fizzing, smoke), Formation of a precipitate (a solid forming in a liquid solution), Color change (unexpected and significant), Temperature change (getting hotter or colder without external heating/cooling), Production of light or sound.

 Physical Change: Change in size or shape, State change (solid, liquid, gas), Dissolving (sometimes, see specific dissolving examples below), Easily reversible (often, but not always).

3. Is physical change always reversible?

Generally, but not always. Some physical changes can be reversed easily (e.g., freezing water, melting ice), but some physical changes are difficult to reverse (e.g., grinding a rock into powder).

4. What is the main difference between a physical change and a chemical change?

Physical change involves the physical state of a substance, but it doesn't change its chemical composition. It means the substance is still the same material, while in a Chemical change, a new substance is transformed with a different chemical composition and properties. It means the substance does not remain the same in this change.


5. Can a change be both physical and chemical?

A change can be both physical and chemical. For example, when you burn wood, the wood undergoes both chemical changes and physical changes. Combustion of wood, creating new substances (ash, gases, etc.), is a chemical change. Simultaneously, the wood undergoes in shape, size, and state; this is a physical change.

6. How can I tell if a change is physical or chemical? What are some clues?

Here are some clues to help you determine the type of change:

  • Clues for Chemical Change: Difficult or impossible to reverse, Production of a gas (bubbles, fizzing, smoke), Formation of a precipitate (a solid forming in a liquid solution), Color change (unexpected and significant), Temperature change (getting hotter or colder without external heating/cooling), Production of light or sound.

Clues for Physical Change: Change in size or shape, State change (solid, liquid, gas), Dissolving (sometimes, see specific dissolving examples below), Easily reversible (often, but not always).

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