Make your own Cloud in a Bottle
To see how clouds form
◊ A one litre plastic water bottle (with a lid)
◊ Warm water
◊ Optional thermometer (small enough to fit into the bottle)
1. If you have a thermometer, put it in the bottle and close the lid tightly. Write down the temperature. See what happens to it as you squeeze the bottle. You should see the temperature increase as the bottle is squeezed and the air inside it is compressed (squashed).
2. Fill the bottle with a few drops of warm water, and put the lid on again. Squeeze the bottle many times and watch what happens.
3. As the warm water evaporates, the amount of water vapour in the air in the bottle increases. When you release the bottle, the pressure, and temperature in the bottle drops. BUT you will not see any clouds forming despite the fact that the air in the bottle is almost certainly saturated with water vapour.
4. Now open the bottle, and light a match (get an adult to help with this step). Hold the match near the mouth of the bottle, then blow it out, holding the smoking end of the match in the bottle for a few seconds before quickly closing the lid tightly.
5. Squeeze and release the sides of the bottle a few times. Now what happens when you squeeze the bottle hard for a few seconds and then suddenly release the bottle? You should see a cloud forming in the bottle when you release it, as the water vapour now has small particles (smoke, soot, ash), known as Cloud Condensation Nuclei, to condense on.
◊ A large, clean, plastic, fizzy drink bottle. Make sure it isn’t cracked or damaged.
◊ Warm water
◊ Optional thermometer
◊ Bike pump
◊ Bike pump attachment, e.g. rubber bung with inner tube valve (you can buy a rubber bung from our shop)
1. Pour a few cm of warm water into the bottle, and swill it round to wet as much of the surface as possible.
2. Firmly push the pump attachment into the neck of the bottle, and pump air into the bottle. If you have a thermometer, you can watch the temperature rise a couple
of degrees as the pressure increases. This encourages the water to evaporate.
3. Release the bottle suddenly. You may see a faint cloud appear. When you release the bottle, the pressure, and temperature in the bottle drop suddenly. However, you will not see many cloud droplets forming despite the fact that the air in the bottle is almost certainly saturated with water vapour (if you do, its probably because your bottle wasn’t very clean!).
4. Now open the bottle, and light a match (get an adult to help with this step). Hold the match near the mouth of the bottle, then blow it out, gently blowing some smoke into the bottle for a few seconds before quickly attaching the bike pump.
5. Now pump air into the bottle again and release it suddenly. You should see a much clearer cloud forming in the bottle when you release it, as the water vapour now has small particles (smoke, soot, ash), known as Cloud Condensation Nuclei, to condense onto.
N.B., you can repeat this experiment using ethanol (or surgical spirit, or alcohol based hand cleansing gels) rather than warm water. In this case, no smoke is required. Ethanol has a substantially greater vapour pressure than water, and such high levels of supersaturation can be achieved as to make nucleation possible without any CCN present.
How does this relate to the atmosphere?
Clouds can only form when the air is saturated with water vapour and when there are condensation nuclei present. Cloud seeding experiments introduce extra Cloud Condensation Nuclei to the atmosphere, to influence the number and size of raindrops in a cloud.