Bottled clouds
Clouds are made of water droplets. Water droplets form on pieces of dust.
What you need
- PET bottle with lid (1.25 L or larger)
- water
- matches
What to do
- Pour a small amount of water into the PET bottle and screw the lid on tightly.
- Shake the bottle to make the sides wet.
- Squeeze the bottle tightly, then release it. Does anything happen?
- Open the bottle.
- 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.
- Squeeze the bottle and release it as you did in Step 3. What can you see?
What's happening?
Shaking the bottle ensures plenty of water vapour (water in the form of a gas) mixes with the air inside the bottle. When smoke is introduced to the bottle, some of the water condenses to make tiny droplets that look like a cloud. The smoke is needed to make this happen because the water droplets form on the smoke particles suspended in the air. The water droplets are white in appearance when they reflect white light.
When you squeeze the bottle, the air pressure in the bottle increases and the water droplets evaporate into the air. Water in its vapour form is invisible so the cloud disappears.
