We had both diet, and regular root beer left over from a buoyancy/density test, for a sink or float experiment, to meet the final requirement on our library's science themed summer reading list...
...and Sunday just happened to be National Ice Cream Day. It only seemed fitting to set up a summer, Sunday science, snactivity with root beer floats for everyone - including a few neighborhood friends who came running, when I called my own inside.
First we talked about nucleation - the process of the carbon dioxide bubbles getting stuck in the craggy, oxygen bubble covered surface of the ice cream, where they sit pulling in more, and more bubbles, becoming larger and larger, creating a frothy, delicious, fat coated foam. Then, I turned the children loose to experiment.
We made some floats by:
- dropping ice cream into the root beer,
- pouring root beer over small scoops of ice cream,
- pouring root beer onto ice cream, that had been pressed, and smoothed as much as possible into the bottom of the cup
- and pouring root beer onto melted ice cream - which made a wonderful root beer fizz.
We used vanilla ice cream and:
- warm regular root beer,
- cold regular root beer,
- warm and cold diet root beer,
- and cold Coke Zero...
...observing the levels and quality of foam, and being delighted to find ice crystals forming in the root beer left to sit on top of the ice cream. Some of our soda sat for a while before we got around to adding ice cream, and just as you might imagine, the foam was nearly as flat as the soda.
Then, just to be sure we were observing a physical change and not a chemical one brought on by combining ice cream and soda, we added some root beer to plain milk.
That brought our experiments to an end, as we switched over to a discussion of Laverne and Shirley, and Laverne's love of milk and Pepsi, and how I always wondered what that would taste like.
If it's anything like root beer and milk, I wouldn't recommend it.
Resources we found handy:
How an Ice cream Soda or Float Works from About.com,
Kitchen Chemistry from Sciencecenter.org,
Fizzics from The Fizz,
and Why is There So Much Foam in a Root Beer Float? from Wonderopolis.