Continuing on our clouds and weather theme, todays activity is making a rain cloud in a jar. You will need: A jar with a lid, 3 or 4 ice cubes, 1/2 a cup of hot water, hairspray.
Pour the hot water into the jar. Swirl it around in the jar, to warm up the sides. Turn the lid upside down and place it on the top of the jar. Pop the ice cubes onto the lid and count to 30. The next bit needs to be done quickly. Lift the lid and very quickly spray the hairspray into the jar. Replace the lid with the ice still on top. Watch the cloud form - my children got really excited when they could see this happening. When you see a good amount of condensation form, remove the lid and watch the “cloud” escape into the air.
Explanation: When you add the warm water to the jar, some of it turns to water vapour. The water vapour rises to the top of the jar where it comes into contact with cold air (the ice cubes on top). Water vapor condenses when it cools down. However, a cloud can only form if the water vapour has something to hold on to. In nature, water vapour may hold onto dust particles, pollen, air pollution, volcanic ash... bits in the air. In our activity, the water vapour attached itself (condensed) onto the hairspray.