Store cupboard science for the festive season – make a rainbow

Layered Sugar Density Rainbows

Christmas movie favourite ‘The Wizard of Oz’ featured a rainbow.  But there’s no need to follow the yellow brick road – have a go at making your own at home?

You’ll need three small glasses, a Calpol syringe,  warm water, sugar and different food colourings.

Half fill the glasses with the warm water. Then add to each glass a different amount of sugar and food colouring.

This is what we did:

Glass 1 – add 1 tablespoon of sugar and 2 drops of food colouring (we used yellow)

Glass 2 – add 2 tablespoons of sugar ad 2 drops of food colouring (we used red)

Glass 3 – add 3 tablespoons of sugar and add 2 drops of food colouring (we used blue).

Using a different spoon stir each glass vigorously until the sugar is completely dissolved in each glass.

Using a calpol syringe transfer half of the blue water into an empty clean glass.  We found a small not so wide glass was the best for this. Next very carefully using the syringe transfer half of the red coloured water on top of the blue water.  It should sit on the top of the blue coloured water.  Repeat again with the yellow colouring – you will see a beautiful, layered rainbow.

The Why?

This store cupboard science uses density to create a layered effect – normally mixing coloured water would give a sludgy colour! Density measures the amount of mass in a particular space, oil molecules are packed less tightly than water molecules making oil less dense so when you mix oil and water it floats on the top when the two are combined (as we have seen in other store cupboard science experiments).  In this experiment we are changing the density of water with sugar. The sugar molecules occupy the space in between the water molecules, making the solution tightly packed and so denser.  The more sugar we add to the water, the more dense the solution. By creating different density solutions we have been able to layer them to create the coloured rainbow

To find out more head to the little passports website.  (This is a link to an external site.)