We had "Fun Friday" yesterday and I was the teacher (as Mowg calls it).
We made Sea Glass Candy--really just hard candy that you shatter and then paint with powdered sugar. We also made shrinky-dinks. The fun part for the grown-ups was we also learned some of the science behind those things.
Did you know that table sugar crystals are made up fructose and glucose (those are molecules)? When you apply heat they interfere with their bond and the crystal disappears. Now fructose and glucose still want to get back together pretty bad so as soon as heat steps out of the picture, they're back together. Unless....you can find something else to interfere. (In steps corn syrup).
I had each of the kids hold a paper on a stick that was one of those four things: fructose, glucose, heat, and corn syrup. We acted out the process. To kids held their glucose and fructose together and then heat pushed them apart and kept them apart. When we back heat off we had corn syrup step in to keep those other two from forming their crystal.
Then we put 1 Cup Sugar, 1/3 Cup Corn Syrup and 6 tablespoons of water in a pot and mixed them together. We added our friend heat to see what would happened to those sugar crystals. They melted!
We had to let it boil until it reached 300 degrees on the Candy Thermometer...or the hard crack stage. At 250 we added the food coloring. We let each kid put in a couple of drops. At this point there's no stirring or that agitation will encourage fructose and glucose to get back together (reforming crystals). The boiling process distributes the color and it's pretty cool to watch. You also have to watch out for "seed crystals" clinging to the side as they add to the encouragement of the our crystallizing molecules (Fructose and Glucose in case you forgot. I would have by now.). So you brush them down with a wet pastry brush. Once the candy reaches the hard crack stage (which is cool to check by putting a small amount into some cold water where it will go immediately from a liquid into a hard candy that cracks loudly. This also allowed for some sampling.) We took it off the heat and added 1 teaspoon of blackberry extract. If you have flavoring oils they work much better. We're going to try again with 1 tablespoon of extract as I couldn't tell that we'd added any flavoring and oils are pretty hard to come by in our neck of the woods. Then we poured it onto a lightly sprayed cookie sheet. It made a huge circle. We left it to cool.
While it was cooling we learned a little bit about polystyrene or Recycle 6 plastic and what happens to it when you apply heat. Apparently when they make it they heat it up, roll it into thin sheets and then cool it quickly. The polystyrene molecules naturally are a bunchy up, randomly clumped crew (or polymer chain if you prefer) and this process straightens them out some. They want nothing more than to get back to their original state so when heat is re-applied as with shrinky-dinks they attempt it. This is what causes them to curl. One of my nieces said as she went into the other room to hang her shrinky-dink ornament on the tree, "Molecules are fun." I agree.
One last thing Amorphous Solids. What do glass and hard sugar candy have in common? Their molecules are randomly linked together, not in an orderly consistent structure. (which sounds like me) This makes them easy to break. (Hmm I'm seeing some parallels here) I asked the kids the above question and my 5 year old niece said, "They both break easy." I was impressed. This also means they fall into the group called Amorphous Solids. Everyone then got a chance to shatter the candy and paint and sample it. Some Amophous Solids taste good!
Happy Fun Friday! I didn't get any pictures, but it was very fun.