* Expansion: When a substance is heated, its particles gain kinetic energy and move further apart. This increased separation between particles causes the substance to expand in volume.
* Density Formula: Density is defined as mass per unit volume (Density = Mass/Volume).
* Relationship: As the volume of a substance increases due to thermal expansion while its mass remains constant, the overall density decreases.
In simpler terms: Imagine a balloon filled with air. When you heat the air inside, the balloon expands because the air particles spread out. Even though the amount of air (mass) stays the same, the balloon gets bigger (volume increases). This means the air inside is less dense.
Exceptions: There are some exceptions to this general rule:
* Water: Water exhibits anomalous expansion. Between 0°C and 4°C, its density actually increases with temperature. This is due to the unique structure of water molecules.
* Phase Changes: When a substance changes phase (like ice melting into water), its density can change significantly, even without a change in temperature.
Let me know if you'd like more details on any specific aspect of thermal expansion or density!
