submitted 1 year ago by sixfold@lemmy.sdf.org to c/science@beehaw.org

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This is a jar full of only water (liquid and vapor). It boils at any temperature when you apply something cold enough to the top, like ice.

cross-posted from: https://lemmy.sdf.org/post/2697716

I put water in a jar and sealed it while it was boiling, and now it boils at any temperature. Super fun demo to try.

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[-] MalReynolds@slrpnk.net 3 points 1 year ago

You are sollidly correct, and your arguments are correct, but TMI (Too Much Information) applies (to me). Be well, indeed live long and prosper...

[-] goddard_guryon@sopuli.xyz 3 points 1 year ago* (last edited 1 year ago)

Paint it as a chemical reaction in order to understand its equilibrium state. We basically have:

H~2~O (gas) ⇌ H~2~O (liquid)

By sealing the jar with the water already boiling, we initialize the system to be in a state with equal(ish) amount of both liquid and gas. Then we allow the system to cool down so that the liquid water is no longer boiling. Now the system sits at an equilibrium between liquid and gas states.

Now, when we put ice on top of the jar, the water vapor condenses and gets converted to liquid, pushing the equilibrium to the right. But this decreases the overall pressure in the system since fewer particles now occupy the volume above the liquid's surface. This is essentially the system trying to pull itself back towards the original equilibrium i.e. towards the left of the equation, which it does by making more water vapor i.e. boiling.

This reaction-like picture helps in visualizing the system better in some cases, so I tried to add it alongside the pressure dynamics scenario. You may be interested in Le Chatelier's principle if you prefer this.