Physical and Chemical Changes: Differences with Examples

Physical and chemical changes are the two ways matter can change. In a physical change, only the form, shape or state changes and no new substance is formed, like ice melting into water. In a chemical change, a new substance with new properties is formed, like iron rusting.

This topic comes up in Class 6 and Class 7 Science and forms the base for chemical reactions in Class 10. Below are the definitions, a comparison table, everyday examples and simple tests your child can use.

What Is a Physical Change?

A physical change alters how a substance looks or feels (its size, shape, colour or state), but the substance stays the same. Most physical changes are reversible.

Examples: ice melting into water (and freezing back); tearing paper; dissolving sugar or salt in water (recoverable by evaporation); stretching a rubber band; folding clothes or crushing a can.

What Is a Chemical Change?

A chemical change produces one or more new substances with different properties from the original. Most chemical changes are irreversible.

Examples: iron rusting; burning paper or wood; cooking an egg; milk turning into curd; digestion of food.

Physical vs Chemical Change: Comparison Table

Point	Physical change	Chemical change
New substance formed?	No	Yes
Reversible?	Usually yes	Usually no
What changes	Shape, size, state, colour	Composition of the substance
Energy change	Small (if any)	Often heat, light or sound given out or taken in
Chemical properties	Stay the same	Change completely
Example	Melting wax	Burning wax

Signs That a Chemical Change Has Happened

1. Gas is given off (bubbles, fizzing) — vinegar and baking soda.
2. Heat or light is produced — a burning matchstick.
3. Colour changes permanently — a cut apple turning brown.
4. A new smell is produced — food that has gone bad.
5. A solid (precipitate) forms when two liquids are mixed.

Careful: a colour change alone doesn't always mean a chemical change. Mixing blue and yellow paint gives green, but that is a physical change because no new substance is formed.

20 Everyday Examples

Physical changes	Chemical changes
Melting butter	Burning a candle wick
Boiling water	Rusting of an iron gate
Making ice cubes	Cooking chapati
Chopping vegetables	Ripening of fruit
Dissolving salt in water	Milk turning into curd
Breaking glass	Lighting a firecracker
Inflating a balloon	Baking a cake
Sharpening a pencil	Digestion of food
Melting wax	Photosynthesis in plants
Evaporation of puddles	Tarnishing of a silver spoon

The Candle: Both Changes at Once

A burning candle is a favourite exam question because it shows both changes: physical — wax melts near the flame and becomes solid again when it cools; chemical — the wax vapour burns, producing carbon dioxide, water vapour, heat and light.

Two Experiments for Home

Experiment 1 (Chemical): put a spoon of baking soda in a glass and add a little vinegar. It fizzes because carbon dioxide gas is formed — a new substance, so this is a chemical change.

Experiment 2 (Physical): dissolve salt in water, then leave it in a shallow dish in the sun for a few days. The water evaporates and the salt is left behind, unchanged — a physical change.

Safety: always do experiments with an adult nearby. Never taste chemicals.

Frequently Asked Questions

What is the main difference between physical and chemical changes?
In a physical change, no new substance is formed. In a chemical change, at least one new substance with new properties is formed.

Is dissolving sugar in water a physical or chemical change?
It is a physical change. The sugar can be recovered by evaporating the water.

Is rusting a chemical change?
Yes. Iron reacts with oxygen and moisture to form rust (iron oxide), a new substance.

Is cooking food a physical or chemical change?
Cooking is usually a chemical change, because heat changes the food into new substances that cannot be turned back.

Are all physical changes reversible?
Most are, but not all. Breaking glass or tearing paper is a physical change, yet you cannot easily reverse it.