Why We Brush Our Teeth

The littler little spent Saturday in bed, feverishly watching television, unhappily missing her Spring Ice Show rehearsal, and barfing every now and then for good measure, which left me and the bigger little to our own devices for most of the day.

Poor Will doesn't know what to do with herself without a sister-in-crime, so she got to have a LOT of Momma time (a little more Momma time than the Momma who's not used to having a bored kid hanging around her feet might necessarily prefer, ahem, but what's a Momma to do?). A LOT of board games:
A LOT of helping Momma sew:
A LITTLE bit of sewing on my own:And a LOT of time for long-lived science projects:Yep, it's your typical Egg in Vinegar project, but it's super-cool and was a huge hit in our family's five-and-a-half population bracket. Along with a couple of other projects that I haven't introduced yet, I used this project to demonstrate why we brush our teeth twice a day.

An eggshell has calcium in it, just like our bones and teeth do (Technically, an eggshell contains calcium carbonate--CaCo3 instead of Ca--but since calcium carbonate is used as a calcium dietary supplement I'm treating it as "calcium" for the sake of the kindergartner). Calcium is what makes our bones and teeth hard, and it's what makes the eggshell hard, too. Vinegar is an acid. Acids are also in juices and lots of foods. The vinegar's effect on the eggshell is a demonstration of the effect that acids also have on our teeth, if we don't brush those acids away very often.

You will need:

• egg
• glass cup or jar
• plenty of vinegar

1. Put an egg in a glass container.
2. Fill the rest of the container with vinegar.
3. Let the egg sit for several hours in the vinegar. We ended up letting the egg sit for about 18 hours, total, although Willow took the egg out periodically to play with it.
4. Pour out the vinegar--

--and notice how the acid in the vinegar has dissolved the calcium eggshell. Sure, the egg is bouncy, but Will didn't really make that much of this. She was mostly interested in handling the egg and looking at the mostly dissolved eggshell, and then she accidentally dropped it down the sink there and it's gone now, and I hope it doesn't clog the drain.

Willow LOVED this experiment. I let her repeat it again immediately, and she was able to set it up entirely by herself, and this time she set up TWO eggs in TWO glass jars, so I suppose that if one drops down the sink again, we'll still have a spare for bouncing.