Here's why:
* Increased Kinetic Energy: Faster-moving particles have more kinetic energy. This energy causes them to vibrate and move around more vigorously.
* Overcoming Attractive Forces: The increased kinetic energy helps the particles overcome the attractive forces between them.
* Increased Spacing: As the particles move further apart, the overall volume of the substance increases.
This principle applies to all states of matter:
* Gases: Gases are already very spread out, so increased temperature causes significant expansion.
* Liquids: Liquids expand less than gases because their particles are more tightly packed.
* Solids: Solids expand the least, but they still expand slightly as their particles vibrate more vigorously.
This is why things get bigger when heated and shrink when cooled.
