Building crystals

WHAT'S THIS SCIENCE BITE ABOUT?

This Science Bite will show you how to make your own crystals using some common kitchen store ingredients. Boiling water is required for this experiment so please remember to ask an adult for help.

Crystals you commonly come across include snowflakes, diamonds and table salt, but we’re going to experiment making crystals with cane sugar (or sucrose).

WHAT YOU'LL NEED

Kit for building crystals science bite

To make crystals from cane sugar:

  • A clean glass jar or tumbler
  • Cotton thread (or pipe-cleaner)
  • Wooden stick (or pencil)
  • Cane sugar
  • Water
  • Food colouring (optional)
  • Saucepan
  • Stirrer (wooden spoon or similar)
  • Paper clip
  • Cling film
  • Time and patience

HOW TO DO THE EXPERIMENT

To start your crystals you need to prepare a saturated solution that contains as much of the solute as can be dissolved in the solvent. So for example, to make crystals from sugar you’ll need about 3 cups of sugar (solute) and 1 cup of boiling water (solvent) before no more sugar will dissolve. The amounts of sugar that will dissolve may vary.

Heat the water till it boils in your saucepan. Remove from heat source. To your saucepan of boiling water, add and stir in 1 cup of sugar. Once that has dissolved, add a second and allow it to dissolve. Then, add the third. If the third cup of sugar dissolves add a little more and repeat till no more will dissolve.

If you like, you can add a drop or two of food colouring to give your crystals some colour.

Carefully pour the solution from the saucepan into the glass jar taking care not to transfer any crystals or undissolved sugar.

In order to ‘seed’ your crystals, add a piece of cotton thread (or pipe cleaner) tied to a wooden stick. At the other end of the thread you can attach a paperclip to keep thread straight. Position the string so that it’s suspended about 3cm above the bottom of the glass. You don’t want it to touch the side or bottom of the glass.

Then, loosely drape some cling film over the top to prevent dust falling in, but still let the solvent evaporate. Sit the jar in a warm, dry place.

Building Crystal Science Bite - sugar dissolved in water with some red food colouring

Now it’s time to sit back and wait for the crystals to grow. Although the crystals will start growing immediately, leave them for as long as you can. This may take anywhere from a few days to over a week.

If crystals start to form on the sides or bottom of the jar, you can remove the crystal and pour the liquid into a clean jar. Then pop the crystal into that jar and solution as before. Doing this repeatedly you may be able to make sizeable crystals.

Sugar crystals formed on string

Once you're happy with the size of your crystals, you can remove them and allow to dry. What do you notice about the crystals?

FIND OUT MORE...

Crystallography looks at the orderly arrangement of atoms in some solids. Crystals are often categorised by their shape or sometimes by their properties. These crystals are made from sugar (sucrose) are molecular crystals characterised by being soft and having a low melting point.

A range of crystal growing kits are available from the GSC Shop.

Crystal growing kits available from GSC Shop

Send us pictures of your crystal growing efforts if you try this for yourself. Tweet your pics to @GSC1 or post them on our Facebook timeline.

Curriculum Links

Properties and Uses of Materials

SCN 1-16a/ 2-16a/ 3-16a/ 4-16a

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