camping

You're welcome! Well it's more complicated than that, and I'll be honest I don't THOROUGHLY understand everything about it.

But the idea is to move the liquid from one canister to the other, that's why the "giving" canister is upside down. But because you're moving the liquid itself, you can accidentally fill the entire canister with liquid, no room for the vapor to expand into when it gets warm, and boom! So be careful. As long as you weigh it you'll be safe 👍 You freeze the receiving can because cold gas has a lower vapor pressure. And you can put the giving can in a bowl of warm (not hot!) water to increase it's pressure and make the transfer happen faster. You'll feel the giving can get cold as you fill the bottom can.

Fun fact, this is how air conditioners work! Take any gas (preferably not flammable, but that exists too), decompress it in a pipe so it boils into a vapor and absorbs a bunch of heat, making the pipe cold and you can blow air over it to cool your house or fridge.

Then that boiled gas vapor goes into a compressor that increases the pressure in a second pipe, enough that the gas has no choice but to condense into a liquid again. This releases all the heat that was captured in the boiling phase. Now you've got a hot pipe, and you put it outside and blow air over it to cool it off, further liquifying it. Then you take the liquid and release it back into the low pressure boiling pipe inside and start the process all over again!