Instructions:

Pour cold water into a glass and add an ice cube.

Pour hot water into a second glass. Be careful! Add some cold water if the water is so hot that it could burn.

Pour warm water into a third glass (by mixing hot and cold water). Be careful not to burn yourself!

Dip one finger into the hot water and another finger into the ice-cold water. Wait for one minute.

Then dip your hot finger into the warm water.

Does the warm water feel hot or cold?

Dip your cold finger into the warm water.

Does the warm water feel hot or cold?

Explanation:

We perceive heat in relation to the temperature of our skin. When you go from hot water to warm water, the warm water feels cold, because it is cooler than your skin. Conversely, when you go from cold water to warm water, the warm water feels hot as it is warmer than your skin. The same thing takes place in your mouth.