All matter is made of particles far too small to see. In a solid the particles are packed tightly in a pattern and only jiggle on the spot, so a solid keeps its shape. In a liquid the particles are still close together but can slide past each other, so a liquid flows. In a gas the particles are far apart and zoom about in all directions, so a gas spreads out and can be squashed.
We know gas particles are real even though we cannot see them. Air pushes on a balloon and makes it bigger. A bicycle pump squashes air into a tyre. When sugar dissolves in tea it seems to vanish, but the tea tastes sweet: the sugar particles are still there, mixed between the water particles.
Worked example
Why can you squash a syringe full of air but not one full of water?
- Gas particles are far apart with empty space between them.
- Pushing moves them closer together.
Answer:Liquid particles already touch, so water cannot be squashed much.
Key words
- particle
- a tiny piece of matter, too small to see
- vibrate
- jiggle backwards and forwards on the spot
- compress
- squash into a smaller space
- matter
- anything that has mass and takes up space
New questions every time.
NGSS-referenced: 5-PS1-1