States of Matter and Particle Theory
The particle model explains solids, liquids, and gases by how their particles are arranged and how much energy they have — not by what they're made of.
Arrangement and movement
In a solid, particles are tightly packed in a fixed pattern and only vibrate. In a liquid, they're close but can move past each other. In a gas, they're spread far apart and move freely and fast.
Changing state
Adding energy (heating) gives particles more energy to break free of their arrangement — melting turns solid to liquid, and boiling/evaporating turns liquid to gas.
Practice
Explain, in terms of particles, what happens when ice melts.