Rainbow Activity 2: Rainbow Pathway

By Farhin Begum

Welcome to the second blog in this rainbow series!

You’ll only need some bits you can find around your house – but it’s very messy so please go outside to have a go! Use a slightly sloping path or patio for the best effect.


CC-BY science made simple.

What you need:

  • 5 different coloured water soluble paints
  • Bicarbonate of soda
  • Plastic sandwich bags
  • Corn flour
  • A teaspoon
  • Measuring jug
  • White vinegar
  • Bowl




Step 1- Mix it well

Get your jug and add 230 ml of white vinegar, one teaspoon of paint and 5 teaspoons of cornflour then mix well.

After you have done that, carefully add it in your plastic bag, but do not seal it yet, and place in the bowl.

Repeat this until you have all the different colours in bags stacked up in the bowl.


CC-BY science made simple


Step 2 – Step into the garden

Go outside and find a suitable place to do this.

Carefully get a bag and pour in 2 teaspoons of bicarbonate of soda and then quickly seal the bags and stand well back!

Turn it into an experiment! Try using a different amount of bicarbonate of soda – what do you predict will happen? Why?


CC-BY science made simple


Step 3 – Expanding!

They will take a few minutes to fully expand and pop.


CC-BY science made simple


Step 4 – Sit back and watch

Sit back and watch the the stream of colour running down your pathway! The paint will wash away with a bit of rain or a spray with the hose.

The bicarbonate of soda reacts with the vinegar and produces a gas called carbon dioxide. The carbon dioxide, CO2, builds up in the bag because it can’t escape. Eventually there is so much pressure inside the bag from the build up of CO2 that the bag pops and the frothy colour spills out down your path!


CC-BY science made simple


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Posted in Activity, Chemistry, Exploring Science, Primary
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