Explaining changes in state
The Three States
Solid – keeps its shape (like ice)
Liquid – flows and takes the shape of a container (like water)
Gas – spreads out and fills space (like water vapor)
What Happens to the Particles?
When heated → particles move faster and spread apart.
When cooled → particles move slower and come closer together.
Example
Ice → (heat) → Water → (more heat) → Water vapor Water vapor → (cool) → Water → (more cool) → Ice
Changes in State
1. Melting (Solid → Liquid)
Happens when heat is added.
Particles move faster and slide past each other.
Example:
Ice melts into water.
2. Freezing (Liquid → Solid)
Happens when heat is removed.
Particles slow down and lock into place.
Example:
Water freezes into ice.
3. Evaporation (Liquid → Gas)
Happens slowly at the surface of a liquid.
Can happen even without boiling.
Example:
Wet clothes drying.
4. Boiling (Liquid → Gas)
Happens when a liquid gets very hot.
Bubbles form inside the liquid.
Example:
Boiling water.
5. Condensation (Gas → Liquid)
Happens when gas cools down.
Particles come closer together.
Example:
Water droplets on a cold bottle.
6. Sublimation (Solid → Gas)
Happens when a solid changes directly into gas.
Skips the liquid state.
Example:
Some air fresheners slowly disappear.
Heating and Cooling
Heating:
Melting
Evaporation
Boiling
Sublimation
Cooling:
Freezing
Condensation
Particle Changes
In a Solid
Particles are very close.
They only vibrate.
In a Liquid
Particles are close.
They move around each other.
In a Gas
Particles are far apart.
They move freely and fast.
Key Words
State
Solid
Liquid
Gas
Melting
Freezing
Evaporation
Boiling
Condensation
Sublimation
Heat
Cooling
Particles
Important Points
Matter does not disappear during a change of state.
Heating gives particles energy.
Cooling removes energy.
Changes in state are usually reversible.