You and Your Students!
Vicki Cobb, Education World Science Editor
Here’s a lesson on solutions and stage craft using hard candy.
Setting the Scene (Background)
Necessity is the mother of invention...
Here's the problem: A play requires an actor go through a glass window. Obviously, since a play is not real, the actor can't go through real glass without doing great harm to himself or herself. So you need something that looks like glass and breaks like glass but won't cut up the actor.
The solution: hard candy. For many years, "candy glass" was used on stage. Today, an expensive "breakaway" plastic is used. The problem with candy glass was that it dissolved in water. It couldn't be used to make bottles that held water that could smash like glass on stage. But your students will be interested to see how hard candy smashes just like glass. So after you're finished learning how candy smashes like glass, you can use the shards to learn something about the science of solutions (how sugar dissolves in a solution).
Have the kids work in groups of two or three.
Give each group two sourballs. Tell them to smash one with a hammer while it is still wrapped in cellophane. They should look at the shards of smashed candy and describe what they see. Do the pieces have sharp edges? (yes) Can those pieces of candy cut you? (no)
Prepare two glasses of water. Put the intact sourball in one glass. Put the shards of smashed sourball in the other. Let the mixtures sit for several days. Keep them covered with foil or Saran Wrap.
Every few hours dip the end of the straw just under the surface of the water. When the straw is removed a small drop of liquid will remain in the end of the straw. Taste that drop. As the candy slowly dissolves in the water, the sugar in the candy will diffuse to the top of the liquid and it will taste sweet. Ask: Which candy disappears first -- the intact sourball or the smashed sourball?
Behind the Scenes
A solution is a mixture where the smallest particles are molecules and the mixture is homogenous -- that means that there is the same amount of sugar at the top of the solution as there is at the bottom.
What is the biggest difference between the smashed sourball and the whole one? (the amount of surface area) Did you need to stir to get the candy to dissolve? (no, you just have to wait long enough) A substance dissolves when its molecules separate from each other and mix into water. You don't even need to stir. Liquid molecules are in motion. That motion causes the sugar molecules to separate and travel through the water. Molecules will continue to dissolve and to travel until all the sugar is evenly dispersed through the water.
Article By Vicki Cobb
Copyright © 2005 Education World