Question

give reason water droplet appear on the outer surface of a tumbler containing ice cold water

Answer 1

It’s a naturally occurring process called “CONDENSATION” .

In nature, the air surrounding us contains water. Not the liquid water but in the gaseous form called “Water Vapor” which is responsible for the formation of water droplets outside a cold container.

Relating to your question, Here’s an example:

You have your favorite ice tea/coffee or any fruit juice with ice cubes in it; after drinking it completely when you keep the glass aside you can see the water droplets forming outside on it. This is due to the reaction of water vapor with the cold surface of the glass which held the cold liquid for a considerable amount of time.

The air containing water vapor in gaseous form reacts with the cold surface which is then converted into liquid water as its molecules slow down and get closer together resulting in the formation of water droplets.

At certain, warmer air can hold more water vapor than the cold air. The outside(surrounding) air is always warmer in nature containing water molecules in it and when it comes in contact with cold surface the reaction occurs as such.

Answer 2

As the water vapour outside the tumbler loses energy and changes into water vapour on coming in contact