Howdy.

Ok, i noticed this a little while ago. I put a soft drink bottle, regular 600ml variety on my kitchen tap. I forced it on so it was tight.
I then turned on the water and held the tap into the bottle, this made a airtight seal. Obviously the pressure built up quite a bit by the time it was around 3/4 full. I took it off, it came off quite easily and made sure it didnt hit the bottom of the sink so it wouldnt make a lound noise and big splash. You can see quite a bit of water vapour comes out of the top of the bottle, like fog or a cloud.

It comes out in whisps and its quite cool looking. I dont know exactly why it does it but its probably because of rapid compression and decompression of water and air. I could be completely wrong. Give it a go, the worst that could happen is a loud bang and a bit of a splash of water, if you are careful you can see this interesting thing.

So would i be right in thinking that the vapour thingy is appearing from the sudden decompression of air etc.?

cheers
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