What causes plastic container with water to “sweat” out water after being frozen and unfreezing?


If a person puts a gallon of water *(of a plastic container)* in the freezer, then take it out later, the water begins to “sweat” through the plastic and some of the water gets wasted, what causes this to happen and does that mean that plastic is getting in the water?

EDIT: *Thank you everybody! I wasn’t going to ask this because I thought it would be a stupid question, but when I did a search online, I couldn’t find anything specific to “plastic sweating water after being cold”. You all helped me realize that I was looking at the situation wrong and it had nothing to do with the plastic itself getting colder or hotter and sweating water but the moisture of air on the plastic being cooled and then warmed up into water droplets.*

In: Physics

The air around the bottle is cooled below the dew point so the moisture in the air condenses on the bottle.

It’s not coming through the plastic.

It’s moisture in the air causing condensation on the plastic.

No water from the inside is lost.

The water does not go through the plastic.

The cold is condensing the air on the outside of the container and that is where the water comes from.

Condensation. Humidity in the air stuck to the outside of the container, goes from humid air to water, then to ice. And in reverse when you take it out. No water leaking through the container, in most cases.

EDIT: Also as it is defrosting in room temperature additional humidity from the environment can attach as condensation

The “sweat” is not from inside the container, but from the air outside the container.

The cold surface causes the humidity in the air to condense into liquid water.

Water expands when it’s frozen, it isn’t leaking through the plastic, that’s just condensation.

The water is in the air around the cold bottle.

The cold bottle condenses the water in the air, and those little bits of water in the air gather into droplets on the bottle.

It might appear to sweat through the plastic because ice takes more volume than the same amount of water. When it turns to water, the volume used is less. The apparent shrinking of ice inside the container, and the condensation on the outside would make it appear to sweat through the plastic, but it doesn’t.