2.0 Thermal Expansions and it's types

2.1 Linear Expansion:
2.2 Area Expansion
2.3 Volume Expansion

When the temperature of a substance is raised by heating or by some other process, the substance expands due to the atoms vibrate and move further apart, on average. All the solids, liquids, gases- generally expand on heating and contract on cooling with few exceptions. The change is very small.