States of Matter and Phase Changes
Phase changes
Changing states
A phase change is a physical change from one state of matter to another. Common phase changes include melting, freezing, evaporation, boiling, condensation, and sublimation.
Common phase changes
| Change | From | To |
|---|---|---|
| Melting | Solid | Liquid |
| Freezing | Liquid | Solid |
| Boiling/Evaporation | Liquid | Gas |
| Condensation | Gas | Liquid |
Particle explanation
During melting and boiling, particles gain energy and move more freely. During freezing and condensation, particles lose energy and move less freely.
Important distinction
A phase change does not make a new substance. Water is still water whether it is solid ice, liquid water, or water vapor.
What is the change from liquid to gas called?
Liquid to gas is evaporation or boiling.
Correct answer: Boiling or evaporation
Does a phase change create a new substance?
Phase changes are physical changes, not chemical changes.
Correct answer: No
What happens to particles when a substance freezes?
Freezing lowers particle motion and locks particles into a more ordered arrangement.
Correct answer: They lose energy and become less mobile
Everyday examples
Ice melting, water boiling, and droplets forming on a cold glass are all common examples of phase changes.