I put water in a thermos and shut it tight. 2 says later I open it and there’s a small release of gas. Why?

Question

I put water in a thermos and shut it tight. 2 says later I open it and there’s a small release of gas. Why?

In: 1

Answer 1

Could be any number of reasons. Temperature changes result in a change of pressure in the gas already in it. Or dissolved gas in the water comes out and since water doesn’t really compress, this changes the pressure of the gas instead. When you open it up, that increase in pressure results in air gushing out.