* Molecular Motion: Heat is a form of energy. When you add heat to a substance, you increase the kinetic energy of its molecules. This means the molecules move faster and vibrate more vigorously.
* Increased Spacing: As molecules move faster, they collide more frequently and with greater force. This increased molecular motion causes the molecules to spread further apart, resulting in an expansion of the substance.
Exceptions:
While most substances expand with heat, there are some exceptions:
* Water: Water is unusual in that it expands when heated between 0°C and 4°C. Above 4°C, it behaves like most other substances and expands with increasing temperature.
* Certain Alloys: Some alloys, like invar, have very low coefficients of thermal expansion. This means they change size very little even with significant temperature changes.
* Phase Changes: When a substance changes phase (e.g., from solid to liquid or liquid to gas), it can either expand or contract depending on the specific substance and the phase change.
Let me know if you'd like to learn more about any of these exceptions!
