Summer Fun 2014 - Sink or Float? Sugared Ice-Cubes

I mentioned the other day that we had done a quick "sink or float" soda pop density experiment, to fulfill the final challenge for our library's summer reading program.  It was a simple - toss cans of diet, and sugared soda into a sink filled with water...

...to see which ones will sink, and which will float type of experiment.  Naturally, the diet soda floats, while the sugared soda sinks.

Actually, my children were more interested in the way the refracting light made the cans appear to shrink into mini-cans, in the water.  Since, it went along so nicely with the color video we had watched to go with our Kandinsky cookies, I let them play for a while...

...before bringing their attention back to the ingredient list on the sides of the cans.  All the cans of soda weighed the same, but they were not all the same when it came to their ingredients.  The sugar in the regular pop increases the density of the liquid, causing those cans to sink.  We also discovered not all diet soda is created equal.  The diet root beer did not have any sugar, but it had an amazing amount of salt, and not surprisingly it didn't float quite as well as the diet Coke (or at least it didn't appear to at the time).

The idea that the density of the liquid inside of a closed can of soda can have more to do with whether the can will sink, or float, than the weight of the can, can be hard to wrap your mind around.  I wanted to be sure the younger children were really getting what was happening, so I prepared a second experiment...

...by filling, and freezing an ice-cube tray, filled half with plain water, and half with sugar dissolved in boiling water to as close to the saturation point as I could take it.

Once the ice was frozen, I plopped one of the plain cubes into a glass of water, and asked the girls if they knew why it floated.  They more or less remembered, that water becomes less dense as it freezes (you can find a more complete explanation, here), which I thought was good enough for an 8 and 9 year old.

I plopped in a sugared ice-cube, and asked the surprised girls why they though it sank, and watched the "light bulb" go on, as I asked them if they remembered why the can of regular soda didn't float, when they diet soda did.

"Sugar!" they yelled, and then, of course, "Can we taste it?"

It's great to be a homeschooler.