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Solids, liquids and gases

Heat and matter · level 2, lesson 1 of 6

A question to start

A brick, a glass of juice and the air in a balloon. What makes each one different?

The idea

Everything around you is a solid, a liquid or a gas. These are the three states of matter.

State Shape Does it flow? Examples
Solid Keeps its own shape No Ice, wood, a brick, a spoon
Liquid Takes the shape of its container Yes, it pours Water, milk, juice, oil
Gas Spreads out to fill any space Yes, everywhere Air, steam, the gas in a balloon

Everything is made of tiny particles, far too small to see.

solidliquidgas
  • In a solid, the particles are packed in neat rows and hold on tight. They only jiggle on the spot.
  • In a liquid, they are still close, but can slide past each other.
  • In a gas, they are far apart and zoom about in all directions.

Worked examples

1. Juice. Pour it from a carton into a glass. It takes the shape of the glass. It is a liquid.

2. A balloon. The air inside spreads out to fill it. Air is a gas.

3. Sand. It pours, but each grain is a tiny solid that keeps its own shape. Sand is a solid made of lots of bits.

Try it

  1. Is milk a solid, a liquid or a gas?
  2. Is a pencil a solid, a liquid or a gas?
  3. What does a gas do when you let it out of a bottle?
  4. In which state are the particles furthest apart?
Answers
  1. A liquid.
  2. A solid.
  3. It spreads out into the room.
  4. In a gas.

Common mistake

"Gases are not really anything." Air is real stuff. You feel it in the wind, and it fills a balloon. Its particles are just far apart.

Where it leads