Cooling the house

The air conditioner is a device that transforms hot air into cold. Before you see how an air conditioner works, remember that air is made up of very tiny particles, called molecules. Molecules are in constant motion, jumping like rubber balls.

When the air is hot, molecules jump at high speed. When the air is cold, they jump very slowly.

When a fast molecule collides with a slow one, the fast decreases its speed and the slow increases it.

The air conditioner slows down fast molecules. Sucks in hot air made up of fast-jumping molecules. When fast molecules collide with slow molecules that are in the apparatus, fast molecules slow down. A fan sends the slow molecules into the room. So, the air coming out of the conditioner is cold.

From hot to cold, from fast to slow jumps, and again, until the air cools the whole room.

The electric refrigerator works more or less the same way. Cool a tank instead of a room.