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Bottled Clouds

A young woman hold up to her face an empty clear plastic 1.25 litre bottle

Is it a cumulus, a nimbus or a stratus? Cloud watching is fun; especially when you can create your own in a bottle.

Australian Curriculum links

  • Science > Earth and Space Sciences > Year 1 > ACSSU019
  • Science > Chemical Sciences > Year 3 > ACSSU046
  • Science > Chemical Sciences > Year 5 > ACSSU077
  • Science > Earth and Space Sciences > Year 7 > ACSSU116
  • Science > Chemical Sciences > Year 8 > ACSSU151

You'll need

  • PET bottle with lid (1.25 L in size or larger)
  • water
  • matches

Try this

Safety: This experiment requires adult supervision. Perform this experiment away from flammable materials.

  1. Pour a small amount of water into the PET bottle and screw the lid on tightly.
  2. Shake the bottle to wet the entire inside of the bottle.
  3. Squeeze the bottle tightly, then release it. Does anything happen?
  4. Open the bottle.
  5. Light a match, drop it into the bottle and screw the lid back on. The burning match will go out when it touches the water.
  6. Repeat step 3.

What's happening?

Shaking the water in the bottle fills the air in the bottle with water vapour (water in the form of a gas). When you squeeze the bottle and release it quickly, the water vapour and air inside the bottle cool down. When smoke particles from the match are also present in the air, this cool water vapour can latch onto the smoke particles and form water droplets, making the cloud that you see.

This is very similar to how a real cloud forms. Water in oceans and on land evaporates (turns from a liquid into a gas) when heated by the sun. This water vapour rises high up into the atmosphere, where the air is at a much lower pressure. When air drops in pressure, it cools slightly. This is why the air inside the bottle cools when you release it. Cold air does not hold onto water vapour as well as warm air. Therefore, as water vapour gets colder, it will try to turn into droplets of liquid water. Small dust particles in the air help these water droplets to form. If the droplets stay small enough, they will form a cloud and stay floating in the air. If the drops get too big, they will start to fall as rain.

Real world links

Stratus, cirrus and cumulus are names given to the most common types of clouds. Three types of clouds that are less known include: mammatus, notilucent and nacreous clouds. Mammatus clouds form in sinking air and are pouch-shaped. They are often seen during severe thunderstorms. Notilucent clouds, or polar mesospheric clouds, are the highest clouds in the Earth's atmosphere. They have a glowing appearance because they reflect sunlight from the other side of the Earth at night. Nacreous clouds, or polar stratospheric clouds, form at very low temperatures and glow brightly before dawn and after dusk. They also contain nitric or sulphuric acid.