My brilliant idea - Make your own

12th December 2008 at 00:00

Science - Ages 7-14

How about growing your own Christmas decorations and learning something about dissolving and evaporation at the same time?

You can grow crystal decorations in different shapes, such as stars or reindeer. To do this you will need salt, which you make into a supersaturated solution by adding hot water to a jar or beaker and adding salt or sugar to the water, stirring until no more solid dissolves. Add a few drops of food colouring to produce different coloured decorations. Let the solution go cold.

Bend some pipe cleaners into the shape of a star or, for the more creative, a reindeer, Santa or Christmas tree. Tie one end of a cotton thread to the shape and the other end to a pencil or piece of wood that lets the shape dangle freely in the solution in the jar.

The trick is to let the water evaporate slowly. Crystals will form on the pipe cleaner. The slower the evaporation of the water is, the larger the crystals.

If you are in a secondary school, you can do this with copper sulphate, borax with some red food colouring, or alum to make different coloured crystal shapes - make sure you perform a risk assessment when using the chemicals.

Salt and sugar decorations are safe to go home but shouldn't be tasted. Other chemicals should remain in school.

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