You’ll need

  • A clear, empty plastic bottle with lid (1.25 L or larger) – a soft drink bottle works well
  • A quarter cup of water
  • Matches

What to do

Warning!

Adult supervision is needed. Candles and matches can be dangerous. Ask an adult for help before using.

  1. Gather your materials on a flat surface.
  2. Pour the water into the plastic bottle and screw the lid on tightly.
  3. Shake the bottle to wet the entire inside of the bottle.
  4. Squeeze the bottle tightly, then release it. Does anything happen?
  5. Open the bottle.
  6. Light a match, drop it into the bottle while it is alight, and screw the lid back on. The match will go out when it touches the water.
  7. Squeeze the bottle tightly again, then release it. Does anything happen?

Questions to ask

Could you make a cloud with the smoke and water? If not, try squeezing the bottle tightly a few more times.

What happened to the air inside the bottle when you squeezed it?

What was the cloud made from? Water or smoke, or both?

What's happening

Water can be either a liquid or a gas, known as water vapour. Water vapour is invisible. Shaking the water in the bottle puts water vapour into the air. When you squeeze the bottle, it puts pressure on the air space inside. When you stop squeezing the bottle, the pressure drops back down, causing the air to cool.

Smoke is made up of gases, liquids, and very small pieces of solids that are called particles. The cool water vapour can stick to these particles to make tiny water droplets. These are not invisible. This is the cloud that you see in the bottle!

This is very similar to how real clouds form. When water in oceans and on land warms up from the Sun, it turns into water vapour (this is evaporation). This water vapour rises high up into the atmosphere, where the air pressure is much lower. When air drops in pressure, it cools slightly. (This is why the air inside the bottle cools when you stop squeezing it.) Cold air does not hold onto water vapour as well as warm air. So, as water vapour cools, the water will change from a gas into droplets of liquid water. Small particles such as dust and smoke help these water droplets to form by giving the water something to stick to. If the droplets stay small enough, they form a cloud and stay floating in the air. If the droplets grow too big, they start to fall as rain.

Did you know

The most common types of clouds are called stratus, cumulus and cirrus.

  • Stratus clouds often look long, flat and grey. They are the lowest clouds in Earth’s atmosphere and sometimes even touch the ground as fog!
  • Cumulus clouds are big, fluffy and mostly white. They are higher up in the atmosphere than stratus clouds.
  • Cirrus clouds are thin and wispy. They are high in the atmosphere and are made of frozen water droplets, which are called ice crystals.

Some less common clouds are called mammatus, noctilucent and nacreous.

  • Mammatus clouds are pouch-shaped and form when air sinks down in the atmosphere. They are often seen during severe thunderstorms.
  • Noctilucent clouds (also known as polar mesospheric clouds) are the highest clouds in the Earth’s atmosphere. They’re only visible from ground level when the Sun is just below the horizon, reflecting sunlight while the sky is dark.
  • Nacreous clouds (also known as polar stratospheric clouds) glow brightly before dawn and after dusk, and form at very low temperatures. These clouds contain nitric acid or sulfuric acid, as well as water vapour.