On my first teaching block I did a density demo for my Grade 9 academic chemistry unit. This demo is available on the web and is very useful for helping students understand what density is. This demo is also great for helping them to realize how bad pop is for them. Being an immunologist with a background in diabetes, I feel compelled to spread the word about the evil of sugary drinks whenever I can. These beverages and other artificial sources of fructose are directly linked to the incredible rise in diabetes.
Back to the demo. You have a can of coke and a can of diet coke, a scale and an aquarium filled with water. You may or may not have already introduced the concept of density. Ask the students what will happen when you put the 2 cans in the water. When you do, the coke should sink to the bottom and the diet coke should float. NOTE, I had trouble when I did a run through because my coke can kept floating. I determined that if you put the cans in upright you may get air trapped in the bottom rim of the can, so put the cans in upside down or on their sides. Once the cans have established their place in the aquarium ask the students why the coke sank and the diet coke did not. Now you can discuss that they are the same volume but different mass. Weigh the two cans and then show them the difference by weighing out the equivalent amount of sugar. This is a dramatic demonstration to them just how much sugar they consume from one can of pop.
Easy, cheap, short density/diabetes demo.
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