Specific Heat of Air and Water

Two clean plastic cups, one filled with room temperature water, the other empty, for a student to test with their finger.

Supported by experience, this is a way to introduce heat capacity as an important variable in measuring temperature.

Make sure the water has been in the room long enough to equilibrate. Cover the water as any evaporation will cool it.

Food safe cups and potable water. And safety glasses, because why not?