Heat trace

Safety

• Carefully review the general safety advice on the back of the box cover before starting the experiment.

Disposal

• Dispose of solid waste together with household garbage.

Scientific description

Obviously, any warm object  gradually loses its heat to its cooler  environment or objects it touches. If you leave two objects in contact for a long time, they will eventually become the same temperature. That’s basically how thermometers work. The passing of heat  from a warm object  to a cold one is called heat transfer.

The thermochromic screen is made using complex technology: it changes colors according to temperature within a range of 24–34 °C (75–93 °F). As you have seen on the screen, the change in temperature occurs only at the very point of contact between your hand and the screen. This tends to result in an intermediate temperature between the two extremes. Our breath is warm, which is why we breathe on our palms when they are cold. The warmth of your breath leaves patterns on the screen, so you can even draw pictures with it!