6+

Hot or Not Pillar

Colourful blue, yellow and red handprints on a black background.
A large grey and black pillar with a sign saying 'Hot or Not' above it. The black pillar has rainbow colours in horizontal bands top and bottom, while there is also colourful hand prints inbetween the bands on the black areas.

Thermocroic liquid crystals change colour when heated or cooled.

How it works

Place your hands on the pillar, then lift your hands to see a coloured imprint.

Things to try or ask around the exhibit

Are your hands hot enough to make the pillar change colour?

Background

The sheets on the pillar contain liquid crystals. They turn blue when warm and red when cold. Liquid crystals are shaped like spiral staircases. When they’re warmed up, the crystals twist tightly and shorten. They shrink to the same size as blue light wavelengths so they reflect blue light and appear blue. When the crystals cool down, they grow longer. Cooled crystals stretch to the same length as (longer) red light wavelengths so the area turns red.

Finding the science in your world

LCD screens have liquid crystals that stop working if they’re too cold or hot because the crystals turn to liquid or solid.