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KS1 Science at Home: Week 2

Key Stage 1 Experiment of the week!

IMPORTANT: this experiment uses hot water so must be competed with an adult.

How does it work?

Skittles density rainbow 6

This experiment is about density. Density is the amount of stuff in something. In this case, the amount of skittle material dissolved in the water. Skittles are mostly made of sugar. When you add hot water to them, the sugar dissolves and the colouring on the shell of the Skittles turns the water different colours. The cup with only two red Skittles doesn’t have as much sugar (stuff) as the cup with ten purple Skittles, but they both have the same amount of water. The red water is less dense than the purple water, so it will float on top of the purple water. This is how the experiment works!

If you wanted to watch the experiment, click here.

Materials you need

  • Water
  • A mug
  • 5 separate cups
  • A Tablespoon
  • A clear glass
  • A dropper or pipette


1. Separate the Skittles into the cups, in these amounts: 2 red, 4 orange, 6 yellow, 8 green, and 10 purple.

2. Heat a mug of water in the microwave for a minute and a half. Be careful removing the water from the microwave – it’s hot!

3. Measure and pour two tablespoons of hot water into each cup, on top of the Skittles.

4. Stir each cup carefully so no water splashes out. The cups need to be cool for the next part of the experiment, so leave them somewhere where they won’t get knocked over. Stir them every ten minutes or so until the Skittles are dissolved (disappeared) and the water is room temperature.

5. Using the dropper, add the coloured water from the five cups to the clear glass. Start with purple, then add green, then yellow, orange, and red last. Go slowly here, we don’t want the different layers to mix.

Questions to think about

1. We added our colours in heaviest-to-lightest order. Does the rainbow still form if you add the red water first, then the orange, yellow, green, and purple?

2. What happens if you stir your rainbow? What if you leave it sitting there over night?

Some Research for next week: What is 'oxidation'?
We will answer this question with next week’s science experiment!