The change in which the shape , size, appearance or state of a subtance may alter but its chemical composition remains the same is called a physical change . In a physical change, no new substance is formed. Any change that involves the formation of a new substance and leads to a transformation of chemical identity is called a chemical change.
Chemical changes are usually accompanied with heat exchanges. Chemical changes are permanent changes which are usually irreversible.
Which of the following involves both physical and chemical change?

Options

A. Burning of a candle
B. Rusting of iron
C. Cooking of food
D. Boiling of water

Answer

To determine which process involves both physical and chemical changes, let's analyze the burning of a candle as an example:

### Step-by-Step Solution:

1. **Identify the Changes in a Candle:**
- When a candle burns, it undergoes two types of changes: physical and chemical.

2. **Physical Change:**
- Initially, the candle is in a solid state. When it is lit, the heat from the flame melts the solid wax into liquid wax. This change from solid to liquid is a physical change because the chemical composition of the wax remains the same (it is still wax).

3. **Chemical Change:**
- As the candle continues to burn, the liquid wax reacts with oxygen in the air. This reaction produces heat, light, carbon dioxide, and water vapor. This transformation of wax into new substances (carbon dioxide and water) is a chemical change because it alters the chemical identity of the wax.

4. **Conclusion:**
- Therefore, the burning of a candle involves both a physical change (melting of wax) and a chemical change (burning of wax to produce new substances).

### Final Answer:
The burning of a candle involves both physical and chemical changes.

---