The Egg Who Didn't Clean His Teeth

My life is largely a collection of projects, from building a pagoda, to unusual room decorations, making costumes and growing fruit and veg, but more on those later ...

Today I'm going to take you through a demonstration I did with my kids:
My six year old asked me why she has to clean her teeth, being a slightly unusual parent I wasn't satisfied with the answer "because otherwise they will rot" and found myself explaining the benefits of fluoride.  The following experiment demonstrated it beautifully and I doubt my children will ever miss cleaning their teeth again!

 Step 1. Take two eggs (these are the 'teeth'), soak one in fluoride mouthwash for around 24 hours (this is 'brushing your teeth with fluoride toothpaste').  One of my children claimed that I should have soaked the other one in water for 24 hours to make it a fair test, I consider this unnecessary but if you really wanted to it wouldn't hurt.  Try to turn the soaking one periodically, I didn't and I wish I had.

 Step 2. Put eggs in jars, make sure you know which one is which (although it will be fairly obvious at the end).  Make sure the tops of the jars are wide enough to get a spoon into otherwise you'll have all sorts of problems getting the eggs out again without making a mess.

 Step 3. Cover eggs with vinegar (this is 'acids in foods which you eat').  The one which hasn't been soaking in mouthwash will immediately be covered in bubbles, the other one will stay remarkably clear of them.

Step 4. After another 24 hours remove the eggs.  The one which didn't 'clean its teeth' will have lost the outer casing of its shell as it has been eaten away by the vinegar.  This makes it soft and squashy to touch, the one which did 'clean its teeth' will have retained its shell at least partially (this is why turning the egg is important, there was a large part of my egg which hadn't coated properly where it was resting on the jar) and will still be hard.