Solids, liquids and gases
Three states of matter
- Everything is made of tiny particles (atoms, molecules or ions) that are always moving — the kinetic particle theory.
- The state depends on how the particles are arranged and how they move.
| Shape | Volume | Compress? | Flows? | |
|---|---|---|---|---|
| solid | fixed | fixed | no | no |
| liquid | of container | fixed | almost none | yes |
| gas | fills container | fills container | yes, easily | yes |
Practice
Which state has no fixed shape and no fixed volume, and is easy to compress?
A gas fills its container and is easily compressed; a solid keeps a fixed shape and volume.
The particle picture
| Separation | Arrangement | Motion | |
|---|---|---|---|
| solid | touching, very close | regular pattern | vibrate in place |
| liquid | close together | random | slide past each other |
| gas | far apart | random | move fast in all directions |
- Strong forces of attraction hold particles together: strong in a solid, weaker in a liquid, hardly acting in a gas.
Practice
In a solid, the particles are:
Solid particles are packed in a regular pattern and vibrate in place; they still move (vibrate), just not around.
Practice
Forces of attraction between particles are strongest in a solid and weakest in a gas.
Strong forces hold a solid's particles in place; in a gas the particles move so fast the forces barely act.
You've got it
Key idea
- a solid has fixed shape + volume; a liquid has fixed volume only; a gas fills its container
- particles are regular and vibrating (solid), close and random (liquid), far apart and fast (gas)
- forces of attraction are strongest in solids, weakest in gases