Rainbows in my kitchen

Author: Mihaela Elena Balint

The rainbow in the bible is a symbol for hope, new beginnings, promises that must be kept. After the Flood, God promised to Noah that He will never destroy mankind again. In fact, there would be no need for any divine intervention. Giving people free will, God made them able to destroy themselves. The entire world is now in a challenging situation. The humankind is forced to re-evaluate its position in relation to nature and the path we choose to go in the future. These days the rainbow becomes a symbol that Everything will be alright! It is up to all of us for these words to turn into reality.

For the activity “Rainbows in my kitchen”, children drew, painted and made a lot of rainbow crafts. They made different types of rainbows with a scientific touch.

Materials used:

  • Salt with big crystals
  • Food colourings, Easter egg dye, or simply painting colours
  • Jar or paper cups for each colour of the rainbow
  • Spoons
  • Paper plates (optional, however, the salt will dry more rapidly on plates)
  • Water
  • A nice bottle or tall jar
  • Some ribbons for decoration.

What you have to do:

  • Put in the paper cup 5 tablespoons of salt
  • Add 3-4 drops of food colouring. The quantity of food colouring or dye depends on the quantity of salt and the intensity of the colour. Add some water. Mix well the salt with the colour.
  • Do the same thing for all the colours.
  • Leave the paper cups for 2-3 days for the salt to dry. It helps from time to time to mix them again.
  • When the coloured salt is dry, pour it in the nice bottle or jar in line with the order of the colours of the rainbow: red, orange, yellow, green, blue, purple, violet. You can prepare only a violet or mauve salt (so, six colours, not seven).
  • Decorate the bottle or jar with a ribbon or/and write a nice message on a label.

The science behind the activity:

  • Salt is solid. In larger or smaller crystals or fine ground, salt is a substance having a very wide range of use. The teacher introduced here information about crystals and the importance and use of the salt in our daily life.
  • Salt dissolves in water. We could talk about the salinity of the sea waters, concentration, solutions and saturated solutions. We also had a mixture of water, salt and food colouring (liquid or powder).
  • Water evaporates during drying of the salty water. After evaporation of the water, only coloured salt remained in the cups. If you put the wet coloured salt on paper plates the evaporation is faster because the rate of evaporation depends on the free surface.
  • Pupils learnt measurements: number of spoons, number of drops related to weights and volumes.
  • Get creative: if you have to your disposal only three colours: red, yellow and blue, can you make the rainbow? Yes, green, orange and different shades of violet can be obtained by mixing two primary colours.

And finally, what is a rainbow? The teacher could enrich pupils’ knowledge about light introducing phenomena like reflection, refraction and dispersion of light.

A spiritual touch could be added to this activity introducing the story of Noah and the Great Flood and talking about the promises and the importance of respecting the given word.

Here is the video about our activities organised for the 2020 STEM Discovery Campaign!