DIY Science: Liquid Rainbow

Layer liquids to make a colourful rainbow.

https://youtu.be/GWYg4XE7a_c

Here's what you need to give this a try at home:

Teaspoon

Clear, tall glass

Food Colouring: Red, Blue

10 - 30 ml each of:

• Vegetable oil – purple (add one drop of red food colouring and one drop of blue food colouring)

• 10ml Honey – (yellow) with dye, red and blue = yellow

• 10ml Whole milk – white

• 10ml Dish soap – green

• 10ml Rubbing alcohol – with dye blue

• 10ml Water – with dye, red

• 10ml 100% maple syrup – brown

Recipe:

1. Decide which of the liquids you think are the most dense ('heavy').

2. Starting with the liquid you think is 'heaviest', pour it slowly into your tall glass.

3. Repeat, pouring in the next liquids you think have the highest density

4. For the last layers, tilt the glass and touch a teaspoon to the inside of it.

5. Pour the 'light' liquids over the back of the spoon to gently add new layers.

6. It’s really important to tilt the jar and pour slow. Otherwise the colours will mix together and you won’t get a distinct rainbow.

7. Optional: Once the last layer has settled, you can try carefully dropping in some tiny objects, like popcorn kernels or plastic beads, to see if where they sink-or-float to.

The science:

Each liquid has a different density, this keeps it in its own layer. The liquids that are higher in the rainbow aren't dense enough to push their way into the layer below.

And because each liquid has the same volume and this part of the equation constant, the only variable is mass. The mass, or weight, of the liquids therefore control their density and resultant position in the rainbow, with honey the most dense (found at the bottom) and water the least (the top).

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