Rock Candy - Chemistry in Action - Science Sundays

This activity is definitely an "adult supervision only" activity. It involves the use of a hot stove and handling hot liquid.

• A wooden skewer or thick string (you can also use a clean wooden chopstick)
• A clothespin(for the skewer) or pencil (for the string)
  
• 1 cup of water
• 2-3 cups of sugar
• A tall narrow glass or jar(a mason jar is perfect for this!)

To start set up the following:

1. Clip the wooden skewer into the clothespin so that it hangs inside the glass about 1 inch  from the bottom. If you are using the string and the pencil, tie the string to the pencil and place it over the glass. The string should hang inside of the glass, also about an inch from the bottom.
   
2. Remove the skewer and clothespin and put them aside for now. You will need this later!

After set up:

1. Pour 1 cup of water into a pan and bring it to boil.
2. Pour about 1/4 cup of sugar into the boiling water, stirring until it dissolves.
3. Begin to slowly add more sugar. Pour a little at a time and stir it dissolves. Keep adding sugar slowly until no more will disolve. (This is when the solution is fully saturated) This  will take time. Each time you add more sugar it will take longer for the sugar to dissolve each time. Have patience! Be sure you don't give up too soon.
   
4. Once no more sugar will dissolve, remove it from heat and allow it to cool for at least 20 minutes.
5. While it is cooling dip half of the skewer in the sugar solution and then roll it in some sugar to help jump start the crystal growth. Be sure to let the skewer cool completely so that sugar crystals do not fall off when you place it back in the glass.
6. Carefully pour the sugar solution into the jar almost to the top. Then submerge the skewer back into the glass making sure that it is hanging straight down the middle without touching the sides.
7. Allow the jar to fully cool and put it someplace where it will not be disturbed.
8. Now just wait. The sugar crystals will grow over the next 3-7 days.

How it works

When you mixed the hot water and sugar you made a saturated solution.  A solution is saturated when the liquid holds as much of the compound dissolved in it as possible. In this type of solution, the molecules are constantly bumping into each other. As they do this, they sometimes stick to each other. In a saturated solution, the molecules bump into one another frequently because there are so many of them. This begins a crystallization process and is called nucleation. Once several molecules are already stuck together, they attract other molecules to join them. This is a very slow process that makes crystals grow.

As the water cools the sugar is forced out of the water solution. The skewer (and sometines the glass itself) gives the sugar something to grow on. With some luck and a whole lot of patience you will have a tasty scientific treat! Enjoy!