Wikijunior:Big Book of Fun Science Experiments/Rainbow columns

INGREDIENTSEdit

  • water
  • salt
  • food colouring

WHAT TO DOEdit

  • Take 2 large spoonfuls of salt and dissolve them in 100mls of water.

  

  • Add a few drops of green food colouring. 
  • Then you take another large spoonful of salt and dissolve it in 100mls of water.

 

  • Then add a few drops of yellow food colouring (if you don't have yellow use any other colour). 
  • Then add a small spoonful of salt and dissolve it in 100mls of water.

  

  • add some red food colouring to that.

 

  • add a bit of food colouring to a test tube.
  • then add another colour of food coloring very very gently.
     
  • add different types of food colouring 2 more times very gently.
  • if it mixes together start again and keep on trying till you get a rainbow.

PrincipleEdit

The principle of this experiment is density. Density is the ratio between volume and mass. When different substances of different densities are added to a container, one frequently floats on top of the other because it has lower density. The perfect example of this is oil on top of gasoline.