Cloud in a bottle

Build your own cloud. PRINCIPLES: Pressure, Heat transfer, Evaporation & Condensation.

What to Do

Put 250ml of hot water in bottle. Light a match, blow it out. Insert smoking match & close lid. Shake the bottle, then compress it & release.

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What is going on?

When you compress a gas it gets hotter, when you let it expand again it will get colder.

When a gas gets hotter more water can evaporate and turn into the invisible gas, water vapour. Releasing the pressure lets the gas expand rapidly & cool. Cooler air can't hold as much water vapour. It will condense back into liquid water.

It is hard for water vapour to condense in clean air, so it condenses on the walls. If there are smoke particles in the air, there are lots of places for water to form little drops - so you get lots of little drops of water suspended in the air - a cloud.

Water & smoke.	Compressing the air creates heat = evaporation of water.	Expand it, water condenses on the smoke particles forming a cloud.

Application?

 Warm moist air rises, as it rises there is less air above it so the pressure reduces & clouds may form. When the pressure reduces, the moist air expands, getting colder. The water condenses around dust in the air creating a cloud. If the droplets of water get big enough they become too heavy and will fall as rain.