Heat energy

The power of contrast.

10 minutes


  • Carefully review the general safety advice on the back of the box cover before starting the experiment.
  • Observe safety precautions when working with boiling water.
  • Disassemble the setup after the experiment.
  • Thoroughly wash any dishware you use in the experiment.

Step-by-step instructions

Water can hold a great amount of heat energy. To extract this energy from water, it must be cooled for a very long time. When frozen, water tries to leech energy from its surroundings.


Another plastic bag of water will take energy from boiling water, then share this energy with everything around it.


When heat travels from a hot object to a cold object through a thermoelectric generator, the generator converts part of this heat into electricity. You’ll know it’s working when the buzzer beeps!


The thermoelectric generator will produce electricity as long as there’s a temperature difference between the two sides.



  • Dispose of solid waste together with household garbage.

Scientific description

If you want to use heat energy, you need to convert it to movement and produce a flow of this heat energy. But how do you do that?

Hot objects  carry more energy  than cold objects , and share this energy readily. When two objects with different temperatures come into contact, the hot object  shares its heat  with the colder object . Cats know this—that’s why they often search for the warmest spot in the room to lie down in. Heat  won’t flow from a cold object  to a hot  one without external influences. What a surprise it would be for a cat to lie on a hot radiator that would steal its warmth! Fortunately, that never happens.

Some pairs of materials not only share heat when brought into contact with one another, but also produce electrical energy . Such materials are used in thermoelectric generators to convert part of this heat energy into electrical energy .

We use these generators in places when there’s no other source of energy , such as in space far from the Sun . Space rovers obtain heat  from nuclear fission  and produce electricity  from that heat .