Sugar Crystal Growth

For our holiday homework, we had to grow sugar crystals! :)

Sugar crystals are grown based on the concept that solubility of a liquid decreases when its temperature decreases.

Materials:
1 pot
1 measuring cup
1 cup of water
3 cups of table sugar
2 glasses (I prefer glasses because it is transparent and you can look through to see how the crystals are growing)
*Note: always have >1 setup in case one fails-that's why I use 2 glasses
2 pencils/knifes
Two pieces of string (should be able to be tied around the pencil/knife and lowered into glass almost but not quite touching bottom of jar-about 1-2cm leeway)
One tray filled with tray (used as a moat to keep ants and other insects from disturbing your setup)


Step 1: Boil a pot of one cup of water.
Step 2: When it has finished boiling, pour in all 3 cups of sugar.
Step 3: Put the 2 glasses on the tray. (Ensure the tray is placed in a place with minimum dust and chance of disturbance)
Step 4: Pour it into the 2 glasses (*BEWARE IT'S HOT)
Step 5: Tie the string to the pencil and slowly lower it in. Ensure string is not touching any part of the glass.
Step 6: Wait. After a week or so, your crystal should grow!

Reference: http://www.kidzworld.com/article/26598-make-your-own-crystals



When the water is boiled, its solubility increases. Hence all the sugar can dissolve in it. However when it cools down its solubility decreases allowing less sugar to dissolve. Hence the sugar that can no longer dissolve crystallises on the string and voila, you have a sugar crystal.

After a week, my crystals are growing both on the string and on the surface of the water :O
But why?

After finding out from my friends, it is better to put a small piece of rock sugar on your string first. The sugar in the water will then gather around that piece of rock sugar. Else there is a high chance it won't grow on your string. That is something I need to take note of in the future.

(I'm not too sure whether that is allowed though)

Try this out at home! You can eat it after it's finished, or even add food colouring to decorate it!

That's all for now!