First, we picked out several different types of candy: chocolate, twizzlers, candy corn, bubble gum, lifesavers, and tootsie rolls. Then we put them one at a time on a plate and microwaved them for up to 1 minute. We observed what changes took place in the microwave, the time it took in the microwave for something to happen, the texture after it came out of the microwave, and the texture after it cooled. Then using the information below and the ingredients in the candy we tried to explain what had happened.
Before we go any further, let me point out some safety issues:
The boiling candy is HOT, hotter than boiling water. DO NOT let your kids touch or taste it. Use a knife to poke at it to see what the texture is like.
Microwaves are electromagnetic waves that are strongly absorbed by water, less so by oil, and even less by starches/sugars or polymers. If you continue to run a microwave without something in it to absorb the electromagnetic waves it can eventually damage your microwave. So do not let your microwave run for 10 minutes or so if your candy does not seem to be doing anything. At 1-2 minutes though, your microwave will not be damaged.
As sugars are heated to high temperatures, they will start to burn. Watch your candy carefully! If you start to see smoke coming from it stop the microwave and check on the candy. If it is turning a dark brown or black, don't keep microwaving it. None of the candies we tried produced a flame, but several did start to smoke before a minute was up (we carried the results outside to prevent the fire alarm from starting).
One other note: all of our "experiments" were easily cleaned off dishes after soaking the dishes for a while. However I would recommend you do not use your priceless china for this.
So now that we know how to avoid accidents, lets get to the chemistry!
The three main ingredients you will find in candy are sugar, corn syrup, and a form of fat.
Sugar is what is called a simple carbohydrate. Picture a small ring made of six carbons, with oxygens and hydrogens attached to the carbons. A simple sugar can be made of one ring or two of those rings connected together. When sugar is heated it starts to carmalize: the sugar molecules rearrange and combine with each other in such a way that water is given off and large chains of carbon/oxygen molecules are formed. These chains have a brown color and are what give carmel interesting flavors. As the sugar continues to be heated it will eventually give off so much water that what is left is the carbon, which is black and flaky (think of the ash left after you burn firewood).
|The remains of a lifesaver.|
Corn Syrup is essentially a sugar syrup. It contains many of the sugar rings connected together. It will also carmalize.
Fat, when heated, will first liquify. This is what we saw with pure chocolate. If the fat continues to be heated it will also brown but in a different way from sugar. Probably what is happening is that the milk solids that accompany the fat in most candies is undergoing a Maillard browning reaction with the sugar that is also present.
|Pure chocolate got soft, but otherwise didn't change.|
Gum is made of an artifical petroleum polymer. It did not seem to react at the temperatures a microwave can produce.
Here are a few more websites that explain heating/burning of foods.
http://www.education.com/science-fair/article/heating-sugar/ is similar to what I suggested above, but dealing with only pure sugar.
http://www.curiouscook.com/site/sugar/ explains carmalization.
http://kitchenscience.sci-toys.com/heating explains the Maillard reactions.