Teaching science with density and tasty drinks

The natural world offers us lots of ways we can teach our kids about science. This idea will teach young children density and make a tasty drink at the same time.

My daughter came from school the other day with homework that discussed density in very abstract terms.  Measuring density is typically done by weighing an object, determining its volume and dividing it out.  For visual learners, this doesn’t work very well because it is all in your head. My daughter didn’t quite “get it” so I decided to try to demonstrate with some pretty and tasty beverages.

This Michigan State University Extension activity is commonly used by bartenders, who use density to make layered drinks that impress patrons and earn them big tips. Obviously, you wouldn’t use alcoholic beverages with children, but the notion can be used to teach the concept of density. This experiment relies on the concept of specific gravity: the density of a liquid compared to water. In general, liquids with more sugar tend to be heavier, and liquids with more fat tend to be lighter. 

Start by filling a tall, clear glass with ice.  Slo-oo-wly pour select liquids below over the ice into the glass, until you have a layer.  Alternatively, you can also pour the liquid over the back of a spoon into the glass.  If you pour the liquid with the higher specific gravity first, it should “float” on the other liquid.  The bigger the difference between the liquids, the more likely it is to work.  For example, pouring corn oil on top of grenadine will almost definitely work, apple juice on orange juice probably will not.

Drink                                     Specific Gravity

Corn Oil                                0.924
Diet Soda                             0.98
Water                                    1
Cider                                     1.012
Tonic Water                        1.02
Gatorade                             1.03
Cola                                       1.04
Apple Juice                         1.05
Orange Juice                      1.05
Cran-Apple Drink             1.07
Evaporated Milk               1.07
Grenadine                          1.18

After you get the layers to set up, ask the kids why they think it happened.  Try pouring things in a different order to see if it still will “layer.” After the kids have experimented for a while, ask them why they think it is happening.  Try to get solids to float on different layers of the liquid.  A coffee bean might float differently than a maraschino cherry. 

Have fun experimenting!

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