when a cold water bottle (like from a fridge, etc.) cools down, why does it become wet on the outside of the bottle?

Question

when a cold water bottle (like from a fridge, etc.) cools down, why does it become wet on the outside of the bottle?

In: 1

Answer 1

The water you find on the outside of the bottle does not come from inside the bottle.

The air around us all of the time has water in it. Sometimes only a little bit (low humidity air) sometimes quite a lot (high humidity air). One of the factors that determines how much water the air can hold is the temperature of the air. Colder air can hold less water than warmer air.

So, when you take that cold bottle and put it on the table, it immediately starts to cool the air around it. That air has water inside of it, and as the air cools it starts to have to much water. So that water has got to get out of the air somehow. And it lands on the bottle itself, since that’s where the cold air is coldest.

The water on the outside of the bottle is coming from the air around the bottle. That air is losing it’s water because the bottle is making the air cold.

This also explains why if your cold bottle contains beer and not water the drops that form on the outside are water and not beer. And also explains what morning due is, it’s the overnight air getting colder and letting out it’s water onto the grass.