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human
[Physics] why do teabags inflate when you pour hot water on them?

I've noticed that when I pour hot water into a tea cup with a tea bag at the bottom, the tea bag inflates. Why is this?
gpt
The hot water makes the air in the teabag hot, which makes it expand, which is the effect you're seeing. The teabag is tight knit enough to not easily release all the air (like the spiders that trap bubbles with webs, you don't need to be air tight to trap the bubbles), but the leak rate is still pretty high, so they usually deflate pretty quickly.

As far as floating after you squeeze the air out with a spoon, that's just because dry tea is buoyant and it takes a while for it to fully soak and sink.