Thermal Expansion
- When a material is heated:
- Its temperature increases
- Its overall volume increases (it expands)
- Its density decreases
- This expansion happens because:
- The molecules start to move around (or vibrate) faster as they gain kinetic energy
- This causes them to collide with each other more often and push each other apart
Thermal Expansion in a Solid
When a solid is heated, the molecules vibrate more, pushing each other apart
- Thermal expansion occurs in solids, liquids and gases
- When temperature is increased (at constant pressure):
- Solids will tend to expand the least
- Gases expand the most
- Liquids fall in between the two
Table Comparing Thermal Expansion of Solids, Liquids and Gases
State | Magnitude of Expansion | Explanation |
Solid | Expands slightly | The low energy molecules cannot overcome the intermolecular forces of attraction holding them together |
Liquid | Expands more than solids | The molecules have enough energy to partially overcome the intermolecular forces of attraction holding them together |
Gas | Expand significantly | The high energy molecules have enough energy to completely overcome the intermolecular forces of attraction holding them together |