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Atmospheric Pressure
You will need:
- A hotplate
- An empty drinks can
- A shallow pan filled with water
What to do:
Put a spoonful of water in the can, and place it on the hotplate. The temperature of the can will rise quickly, and the can will fill with water vapour. At this stage, the air inside the can is warmer than the surrounding air, but the pressure inside the can is the same as outside. Quickly grab the can (using something heat proof!) and plunge it opening down in the water in the pan. After a few moments, as the water vapour in the can condenses and the pressure inside the can falls lower than the pressure outside. The can should crumple with a 'pop' sound.
NB, if you used something more sturdy than an aluminium can, you would find that water would have time to flood into the container to equalise the pressure.
The motion of the atmosphere and oceans is driven by local differences in pressure. At any one point in time, the pressure at sea level may vary around the world from as little as 870mb (inside a hurricane) to 1083.8mb (recorded in Agata, Siberia, on 31 December 1968).
