What you need:
1 clear plastic 2 litre bottle (remove label)
1 sheet black construction paper
matches (Please exercise caution when doing this experiment with young children)
What to do:
• Pour just enough very hot tap water into the bottle to cover the bottom.
• Place your mouth over the top and blow into it to ensure that the bottle is fully expanded. Seal the bottle immediately.
• Shake the bottle vigourously for one minute, to disperse the water molecules in the air.
• Light a match. Let it burn for two seconds then drop it into the bottle. Quickly recap the bottle.
• Lay the bottle on its side with the black paper behind it. Press hard on the bottle for ten seconds. The bottle will be strong so don’t be afraid to press really hard. Release, observe and repeat until a cloud forms.
• When the cloud has formed, quickly unscrew the cap. You should see the cloud escpae from the bottle. If not, give the bottle a light squeeze.
By following the steps you have created the conditions necessary for cloud formation; water vapour in the air, smoke particles for water to collect on, and cooling of the air by lowering the air pressure within the bottle. And there you go – instant cloud formation! Clouds form when condensation collects dust particles, which you provided with the smoke from the match.