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Activity

Growing sugar crystals

Summary: 
Grow crystals from table sugar (sucrose). Look at their shape and/or eat them.
Science content (2016 curriculum): 
Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)
Chemistry: Crystals (7)
Materials: 
  • three cups of sugar and one cup of water, or equivalent
  • heat-proof cup or bowl to hold sugar and water
  • microwave, or stove top
  • wooden spoon
  • optional: shallow, clear baking dish
  • optional for eating crystals: popsicle sticks, clothes pegs and a plastic mesh that lays over the baking dish (e.g. garden store tray for plant pots)
Procedure: 

To make a sheet of sugar crystals:
Combine the sugar and water in the heat-proof container. Heat on a stove top to dissolve the sugar, stirring to help the sugar grains dissolve. Be careful not to heat it to much so that it boils over. The sugar solution is very hot, so best if an adult handles it while heating.
Pour into a shallow baking dish, or leave in the container it was heated in. A shallow layer will yield more crystals.
Place in an undisturbed spot. Crystals are seen in two days, a week is best to allow the crystals to grow larger.

The crystals form as the sugar molecules dissolved in the water come out of solution, to form a solid.

Crystals grow down from the surface or up from the bottom of the tray. Chip out a group of crystals and rinse very briefly in cold water to remove the sugary syrup. Allow to dry. Look for the shape of the sugar (sucrose) crystals. They are monoclinic prisms.

To make sugar crystals to eat:
Students will love to eat the crystals that they make. They are pure sugar, so very sweet - only a small amount for a child is needed.
After pouring the hot sugar solution into a baking dish, lay over the mesh. Students write their name on a popsicle stick, then are assisted in lowering the popsicle sticks through the mesh into the sugar solution. Use a clothes peg to support the stick on the mesh.
Crystals will grow on the popsicle stick where it is immersed. The sticks will need to be chipped out of the layer of crystals that form on the top of the sugar solution. Once the syrup is licked/washed in cold water off the crystals, their shapes can be seen quite well.

Notes: 

There are other methods for growing larger sugar crystals on a stick, but they are tricky to pull off in a classroom setting.

Grades taught: 
Gr 3
Gr 4
Gr 5
Teacher: 
Ingrid
Sonia Ko
Sonja Watson
Teaching site: 
JEMZ+ After school science
Laurier Elementary