Chapter 2 · ICSE Class 7 Chemistry (Selina Concise)

Physical and Chemical Changes

Learn to distinguish physical changes (reversible, no new substance formed) from chemical changes (new substance formed).

🔄 Chapter 2

Physical change versus chemical change, using ice melting and paper burning as examples Ice melting into water is a physical change since no new substance forms, while paper burning into ash and smoke is a chemical change since new substances are formed 🧊→💧 📄→🔥 Physical Change No new substance Chemical Change New substance formed
2.1

Physical Changes

A physical change alters the form or appearance of a substance without forming a new substance, and is usually reversible.

1

Is melting ice a physical or chemical change?

Physical change, since it's just a change of state and can be reversed by freezing

2

Is tearing paper a physical or chemical change?

Physical change, since the paper's chemical composition doesn't change

2.2

Chemical Changes

A chemical change forms one or more new substances with different properties, and is usually not easily reversible.

1

Is burning wood a physical or chemical change?

Chemical change, since new substances (ash, smoke, gases) are formed that can't easily be turned back into wood

2

Is rusting of iron a physical or chemical change?

Chemical change, since iron reacts with oxygen and moisture to form a new substance (iron oxide/rust)

Practice

Exercises

1. Is dissolving sugar in water a physical or chemical change?

2. Is cooking an egg a physical or chemical change?

3. Give one sign that a chemical change has occurred.

4. Is freezing water a physical or chemical change?

5. Is digestion of food a physical or chemical change?

Next chapter — Elements, Compounds and Mixtures 🧪 →