Background:

Crystals are some of the most beautiful naturally occurring objects. A quartz crystal looks as if the edges have been carved but when you look at them in more detail you may be able to see growth lines covering the faces. These lines show that the crystal has been formed by the

growth of one layer after another across the face. In this experiment you will grow sodium chloride (table salt) crystals and sucrose (sugar) crystals. There is a limit to the amount of solid (solute) which will dissolve in water. When the solution cannot dissolve any more solute it is said to be a saturated solution. Crystals grow in a saturated solution that is allowed to cool down and become supersaturated. The more solute in the solvent the faster your crystal will come together. This process of making new crystals is called nucleation.

  • Kettle (adult supervision recommended)
  • x2 clean jam jars or x2 mugs
  • granulated sugar
  • table salt
  • food colouring (optional)
  • spoon
  • Pencil
  • Cotton thread or string
  1.  Tie a piece of cotton thread (or string) to a pencil. The thread/string should be able to hang into your jar/mug without touching the bottom or sides.
  2. Using a kettle boil water. Fill your clean jam jar/mug approximately ¾ full with hot water. Ask an adult to help!
  3.  Add a couple of drops of food colouring to the hot water (optional).
  4.  Add one heaped teaspoon of sugar to the hot water and stir.
  5.  Repeat step 3 until no more sugar dissolves (so it is saturated) but not so much that it doesn’t all dissolve.
  6.  Balance your pencil across the top of your jam jar/mug and let the string dangle into the solution, make sure the string is not touching the bottom or the sides of your jam jar/mug.
  7.  Place in a safe place and leave for a few days/a week.
  8.  Repeat using table salt as your solute, using a different jam jar/mug.
  9.  Compare the crystals formed.
  • Where there any differences in the crystals? What did you observe?
  • Repeat the experiment, this time place your jam jar/mug in the fridge, what effect if any did this have?

What did you discover?
What is the ultimate crystal growing technique?

Tweet or email your conclusions/findings to:
#chemistry4all #LJMU_CfA #kitchencrystals4all  chemistryforall@ljmu.ac.uk

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