What are we doing to help kids achieve?
Some of my classes are working on a unit that involves percent composition, empirical and molecular formulas and hydrates. Those topics have similarities and can be tied together. As we start percent composition it is nice to do a quick demonstration to get the students attention. Food seems to be a great way to get any teenager's attention (See Percent Composition of an Oreo Cookie). Solving for the amount of sugar in a piece of chewing gum is also a simple method to demonstrate percent composition.
First, I ask if any students want to chew sugary gum in class (a line quickly forms). Students take the mass of the gum ("pre-chewed" gum) and start chewing. We discuss the ingredients in the gum. The gum contains mainly gum base and sugar. I introduce the idea of percent composition as they chew the gum. Students learn that they are "extracting" sugar from the gum. The extraction is "finished" when the flavor is gone (about 10 minutes). The mass of the "chewed" gum is much less than the "pre-chewed" gum. The difference is the amount of sugar. A nice feature is that the label usually contains the amount of sugar for every piece of gum (theoretical amount). The amount of sugar (experimental) divided by the whole amount, the "pre-chewed" mass, times 100 is the percent of sugar in the gum. Students are usually surprised at how much sugar is in a piece of gum and how close their results are to the mass of sugar on the label. We then have a general discussion about cavities and percent error.
It is not uncommon for students to get within about 10% error from the actual value on the label. This is a nice, easy, quick demonstration to introduce a concept that we typically do each year. Do you have a method that works for you? How about posting a comment below.......
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