Solids, Liquids and Gases
≈ 20 minAll the matter around you is found in one of three states: solid, liquid or gas. We tell them apart by how they behave, not by what they are made of.
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Fixed | Takes the shape of the container | Fills the whole container |
| Volume | Fixed | Fixed | Not fixed — spreads out |
| Can it be compressed? | Almost not at all | Almost not at all | Easily |
| Does it flow? | No | Yes | Yes |
| Typical density | High | Fairly high | Very low |
Examples from one kitchen: a steel pot (solid), the water in it (liquid), the steam above it (gas). Same street: a brick wall, the water in a Jojo tank, the butane in a gas bottle.
Worked example. Classify each of the following and justify it: milk, a soccer ball, the air inside the soccer ball, mielie meal.
- Milk — liquid: it takes the shape of the jug but keeps its volume.
- The ball's leather — solid: fixed shape and volume.
- The air inside — gas: it fills every part of the ball, and you can squeeze more in with a pump.
- Mielie meal — solid. This one catches people out because it pours. But each individual grain has a fixed shape and volume; what flows is a pile of many tiny solids, not a liquid.
Which state of matter has a fixed volume but takes the shape of its container?
Which state of matter can easily be squeezed into a much smaller space?
A learner measures 250 mL of water in a measuring cylinder and pours all of it into an empty 400 mL bottle. What is the volume of the water in the bottle, in millilitres?
Mielie meal pours out of a bag much like a liquid pours out of a bottle. Why is mielie meal still classified as a solid?