Explore how chemicals and materials change colours when exposed to heat or cold 

Learners will start to notice thermochromic materials everywhere!

Skill development

Children will develop their working scientifically skills by:

  • Asking their own questions about scientific phenomena.
  • Selecting and planning the most appropriate ways to answer questions, including:
  • Researching using a wide range of secondary sources of information.

Learning objectives

  • Compare and group together everyday materials on the basis of their properties, including thermal conductivity.
  • Give reasons, based on evidence from comparative and fair tests, for the particular uses of everyday materials.

Concepts supported

Children will learn:

  • That a change in temperature can have an effect on a material or object.
  • That the properties of a material will affect its suitability for different purposes.


  • A selection of thermochromic materials including: thermochromic film, smart putty, heat-sensitive spoons and rubber ducks, forehead thermometers, car and radiator temperature sensors
  • A hot water bottle
  • An ice cube bag


Learners will be allowed to handle the materials and experiment with placing them on the heat source (hot water bottle) and cold source (ice bag). 

Health, safety and technical notes

  • Be careful with the hot water, keep the kettle out of sight.
  • Check the surface temperature of the hot/cold bag isn’t too hot/cold
  • Don’t allow students to keep their hands on the hot/cold bag for a prolonged period

What’s the chemistry?

Things appear coloured because they absorb and reflect certain wavelengths of light. When thermochromic materials absorb heat, their chemical or physical structure changes so that they absorb and emit different wavelengths of light, and look a different colour.

Suggested activity use

This activity can be used as an interesting hook to engage learners with the idea that a change in temperature can have an effect on a material or object. This nicely leads on to looking at changes of state and what happens to solids, liquids and gases at different temperatures.

Alternatively, you could use the thermochromic materials to stimulate discussion about where they could be useful in everyday life. Learners could then research where they are actually used and create fact files about this, creating a cross-curricular link with Literacy.

Practical considerations

A range of thermochromic products will be required to carry out the activity.