These thermochromic sheets change colour when influenced by changes in temperature demonstrating a difference in temperatures and providing an exciting way to see thermal mapping changes through colour. The sheets can be used from Key Stage 1 all the way through to Key Stage 4 to demonstrate Conduction Insulation Convection Radiation and Friction plus many other experiments involving temperature change.The sheets are printed on one side with Thermochromic Liquid Crystal and have a black backing on the other side. The colour change of the TLC can be viewed through the clear uncoated side of the sheet. The sheets come with a pressure sensitive adhesive backing and the protective release liner can be removed for easy adhesion to a variety of flat services. The thermocolour sheets turn from black to red at a given temperature and as the temperature is increased pass through the colours of the visible spectrum in sequence before turning black again at a higher temperature. The colour changes are reversible and on cooling the colour change sequence is reversed.Liquid Crystals are organic chemicals with twisted helical molecular structures which expand or contract with increases or decreases in temperature not unlike a spring. The result is different wavelengths of incident light being reflected from the slightly changing structure which our eyes see as changing colours. The sheets can be made in a variety of temperature ranges but the most common temperature used in school science projects is 25°C and has a 5°C band-width of green. These sheets can be used in a wide variety of Science experiments. Liquid Crystal is highly accurate in its temperature reading and completely safe to use in the classroom.The sheet size is 150 mm x 300 mm however you can cut the sheet as most experiments can be conducted using much smaller pieces.