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How to Grow Crystal Sucrose

Making crystals offers students a fun, hands-on demonstration of a few important scientific concepts, including the variation of solubility with temperature and the formation of chemical crystal structures. In this experiment, students dissolve sugar in boiling water until the solution is saturated -- meaning that it has dissolved all the sugar it can. As the solution later cools, the sugar becomes less soluble and precipitates out of solution, clinging to a string in the water and building up into a crystalline solid.

Things You'll Need

Sugar
Scoop
Weigh scale
Graduated beaker
Kettle
Water
Stir rod
Wooden stick or pencil
String
Watch glass

Instructions

- 1
  Boil water in a kettle. You will need at least 150 mL.
- 2
  Tie a piece of string several inches long to the center of a wooden stick or pencil.
- 3
  Weigh out approximately 110 g of sugar and set it aside.
- 4
  Pour approximately 150 mL of the boiling water into a beaker. Use the graduations on the side of the beaker to know when you have added the correct volume.
- 5
  Add the sugar to the boiling water in the beaker. Start with a small amount and stir until it dissolves. Slowly add the remainder of the sugar in small amounts, stirring each time. Stop adding sugar when you notice that the sugar is no longer dissolving.
- 6
  Place the stick or pencil horizontally across the open top of the beaker, so the string hangs down into the water. The string should hang down at least halfway. You may need to prod it with the stir rod to get it to hang vertically downward. Don't allow the string to touch the bottom of the beaker; if it does, rotate the stick to wind some string around it.
- 7
  Cover the top of the beaker with a watch glass to prevent excessive evaporation of the water.
- 8
  Set the beaker aside for a few days.
- 9
  Look at the beaker at regular intervals. Sugar crystals will begin to form around the string as the sugar precipitates out of the cooling solution. Remove the string to more closely observe the sugar crystals after a few days.

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