I get the equation. If pressure drops so must the temperature. If you increase the vessel size, the temperature will rise. Math makes sense that way.

But what the fuck is physically GOI g on to cause these temperature swings when dealing with gasses? If I use a bunch of propane on my camper grill, ice forms on the cylinder because it got cold. But why did it get cold? What physically is going on to force the temperature to drop?

Glasses of water dont freeze when you pour them out, why do flow of exiting gasses cause this?