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ARCHIVED - Science activity: Growing sugar crystals

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Crystals form in different manners. Snow crystals grow directly from moist air — i.e. from water vapour. Growing other crystals from liquid solutions is easy to do with your children or students.

Materials

  • 250 ml distilled water (with no impurities)
  • 375 – 500 ml white, granulated sugar
  • 1 paper clip
  • 1 popsicle stick
  • string
  • 1 tall, thin glass jar
  • small saucepan
  • food colouring (optional)

Instructions

  1. Pour the water into a saucepan and carefully bring to a boil. Remove it from the stove.
  2. Gradually stir the sugar into the hot water, a spoonful at a time, stirring after each spoonful to dissolve. Keep adding sugar to hot water until no more will dissolve (you have made a “supersaturated” solution).
  3. Pour your solution into the tall, thin jar.
  4. Cut a piece of string that is about two mm shorter than the height of the jar. Tie one end to the centre of the popsicle stick and attach a paper clip to the other end.
  5. Rub a few grains of sugar along the string.
  6. Slowly lower the string into the solution, making sure that the paper clip does not touch the bottom of the jar. Rest the popsicle stick across the rim of the jar.
  7. Let the solution cool and allow it to rest for about five days.

What happens?

Sugar crystals should start to grow along the string after several days. The grains of sugar on the string act as the seeds on which crystals dissolved in the water are deposited. The longer the solution remains undisturbed, the larger the crystals grow. If you add food colouring when you prepare the solution, then the sugar crystals will be lightly coloured.

For more science activities for youth, visit NRC’s Student Science & Tech site. End