Have you ever wondered how clouds form?

What you’ll need

What you do

1. Place just enough warm water in the bottle to cover the bottom.

2. The next step is to get some smoke particles into the bottle. Light a match and let it burn for a few seconds. Blow the match out and immediately place the head of the match in the bottle. Let the smoke from the match fill the bottle. After a few seconds, the smoke will seem to disappear, but the invisible particles are still floating around in the bottle.

3. Screw the cap on the bottle being careful not to let too much smoke out of the bottle.

4. Squeeze the sides of the bottle really hard 6-7 times (more squeezing may be necessary). Squeeze the bottle again, hold the squeeze for a few seconds and then quickly release the squeeze. The second you release the squeeze, you should see the formation of a little fog in the bottle. This is the cloud!

What happened?

By following the above 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. Voila! Instant cloud formation.

Even though we don't see them, water molecules are in the air all around us — it's called water vapour. When the molecules are bouncing around in the atmosphere, they don't normally stick together.

Squeezing the sides of the bottle forces the molecules to squeeze together or compress. Releasing the pressure allows the air to expand, and in doing so, the temperature of the air becomes cooler. This cooling process allows the molecules to stick together more easily forming tiny droplets and clouds are nothing more than tiny water droplets!

The smoke in the bottle also helps this process. Water particles will group together more easily if there are solid particles in the air to act as a nucleus. The invisible particles serve as a nucleus and help in the formation of the cloud.