Clouds in a bottle

In this video Sylvia demonstrates how changes in pressure result in cloud formation, using a plastic bottle and a bicycle pump.

The bike pump increases the pressure, and therefore the temperature in the bottle and encourages evaporation. Once this pressure is released, the temperature falls and condensation forms. Cloud forms in the bottle when there is more condensation than evaporation.

This demonstrates what also happens in the atmosphere. When the pressure falls and the rate of condensation is higher than the rate of evaporation, cloud droplets form.

Then Pete recreates this demonstration using a demijohn bottle in one of the University of Reading’s laboratories.

How do you think the state of the atmosphere in the room you’re in – the temperature and humidity – might affect the cloud that forms? We look forward to hearing your thoughts in the Comments area within this Step.