Class 7 Science Chapter 5: Changes Around Us – Physical & Chemical

1. Multiple choice questions.

1. Which of the following is a chemical change?

• (a) Melting of ice
• (b) Chopping of wood
• (c) Rusting of iron
• (d) Cutting vegetables

Answer: (c) Rusting of iron.

2. Which one of the following changes cannot be reversed?

• (a) Melting chocolate
• (b) Boiling water
• (c) Cutting a piece of paper
• (d) Freezing water

Answer: (c) Cutting a piece of paper.

2. Answer the following questions in about 30 words.

1. Differentiate between a physical change and a chemical change.

Answer: A physical change alters only the physical properties (like size, shape or state) without forming a new substance, while a chemical change forms one or more new substances through a chemical reaction.

2. Give two examples of physical changes and two examples of chemical changes.

Answer: Examples of physical changes: ice melting, cutting a piece of paper. Examples of chemical changes: rusting of iron, reaction of baking soda with vinegar which forms a new gas (carbon dioxide).

3. Explain why making chapatis from dough is a physical change, but cooking them is a chemical change.

Answer: Rolling dough into chapatis changes its shape and size only, so it is a physical change. Cooking chapatis produces new substances due to heat, thus making it a chemical change.

3. Answer the following questions in about 150 words.

1. What are reversible and irreversible changes? Give four examples of each from daily life.

Answer: Reversible changes are those that can be undone and the original substance can be recovered, such as melting of ice, freezing water, boiling water, and folding paper. Irreversible changes are permanent and cannot be undone, like rusting of iron, cooking food, burning paper, and ripening of fruits. In reversible changes, no new substance is formed, while in irreversible changes new substances are often formed.

2. Describe how burning a candle illustrates both a physical and a chemical change.

Answer: When a candle burns, the wax near the flame melts and becomes liquid (a physical change since it can solidify again on cooling). The wax vapour then burns, reacting with oxygen to produce carbon dioxide, water vapour, heat and light – a chemical change as new substances are formed and the process cannot be reversed.

3. Environmental changes can be both beneficial and harmful. Discuss with examples from the chapter.

Answer: Some environmental changes like formation of soil by weathering rocks are beneficial and lead to the development of fertile land for agriculture. However, changes caused by human activities, such as increased combustion of fuels, add more carbon dioxide to the atmosphere, which can damage the earth’s protective layers and cause harm to the environment. Ripening of fruits (desirable) and decaying of food (undesirable) are also examples.

4. Match the following.

Changes Around Us: Physical and Chemical – Key Concepts for Class 7 Science

Learning the difference between physical and chemical changes is crucial for Class 7 students. Understanding what happens when substances react or change state can help build a strong science foundation for higher classes and competitive exams.

With plenty of real-life examples like rusting of iron or melting ice, this chapter builds curiosity. Exam questions often test your conceptual clarity, so focus on the observable features of each change in your daily life.

Practice identifying reversible and irreversible changes in activities and MCQs. Use diagrams and always note when a new substance is formed to excel in the “Changes Around Us: Physical and Chemical” chapter for the 2025-26 session.