Fun Science: Melting Crayons

Have you ever wanted to make your own unique picture using melting crayons?  With this exciting experiment you can create your own colourful pictures using the power of heat. This experiment will help children to understand how to turn a solid into a liquid with heat.

Colourful melted crayons

You will need:

  • A plain white canvas
  • A pack of different coloured wax crayons
  • Super glue
  • Hair dryer.

Method:

  • Glue all of the crayons in a straight line at the top of the canvas. You need to wait for the glue to dry thoroughly before moving onto the next step.
  • Lean the canvas against something so that it is propped up at an angle. If you are using a wall you may wish to place lots of newspaper around the canvas and on the wall to ensure any mess can be cleaned up easily. You could also try leaning it against cups or a box.
  • Use the hair dryer to start melting the crayons – this may take several minutes. Make sure an adult does this step as hot wax can burn!
  • Wait a few minutes for your picture to dry and display it proudly!

The Science Bit:

Wax crayons are made primarily from paraffin wax and color pigment. This process is the same for all wax crayon colors. The paraffin wax is melted and mixed together with pre-measured amounts of color pigments.

Colour makes a big difference. The pigments, which give each crayon its colour, don’t react the same way to heat. Darker crayons will melt faster because they absorb heat more easily than lighter pigments.

Changing States

The atoms and molecules don’t change, but the way they move about does. Water, for example, is always made up of two hydrogen atoms and one oxygen atom. However, it can take the state of liquid, solid (ice), and gas (steam). Matter changes state when more energy gets added to it. Energy is often added in the form of heat or pressure. So for this example the crayons are getting energy from the heat and this makes the crayons melt. Liquid molecules are looser and can move about easily.

As the picture dries the crayons will become a solid again. When solid, the molecules are held tightly together and they don’t move easily.