Why does a balloon deflate when brought to room temp after staying inflated in a cold car for weeks?

Question

I was cleaning out my car yesterday and found [this balloon](https://imgur.com/a/xK98QRw) from a month ago that was somehow still mostly inflated. Then I brought it inside for my kids to play with and by this morning it had deflated to about ¼ of it’s previous size. Shouldn’t it have gotten bigger as heat makes things expand?

In: 1

Answer 1

Air diffuses through a balloon. Left long enough in the car, this will tend toward the temperature, pressure, etc. of the car (which will be a net loss of molecules). This process is slower than just the temperature expansion. Brought back to room temperature, where the pressure is higher, the pressure outside the balloon will be higher on the inside of the balloon (even once the molecules inside heat back up) and shrink it.