Name two subtances which expand on heating.

Answer

**Step-by-Step Solution:**

1. **Understanding Thermal Expansion**: When substances are heated, their particles gain energy and move more vigorously, which usually causes the substance to expand. This phenomenon is known as thermal expansion.

2. **Identifying Substances**: We need to name two substances that expand when heated. Common examples of such substances include metals, as they typically exhibit significant thermal expansion.

3. **Choosing the Substances**:
- **Brass**: Brass is an alloy of copper and zinc, and it expands when heated due to the increased movement of its particles.
- **Iron**: Iron is a metal that also expands upon heating, as the kinetic energy of its atoms increases with temperature.

4. **Final Answer**: The two substances that expand on heating are brass and iron.

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