* Thermal Expansion: When heat is added to a substance, its particles gain energy and move around more. This increased motion causes the particles to spread further apart, resulting in an increase in volume. This is known as thermal expansion.
* Thermal Contraction: Conversely, when heat is removed, particles lose energy and move closer together, leading to a decrease in volume. This is called thermal contraction.
Exceptions:
* Water: Water is a notable exception. When water is heated from 0°C to 4°C, its volume actually decreases, even though heat is being added. This is because the structure of water molecules changes in this temperature range.
* Phase Changes: When a substance undergoes a phase change (e.g., solid to liquid, liquid to gas), there is a significant change in volume even though the temperature might not change much.
In Summary:
* Generally, adding heat causes a substance to expand, while removing heat causes it to contract.
* Water and phase changes are important exceptions to this rule.
