For our Active Learning period this week, I have explained to the children the importance of brushing their teeth several times each day. To help emphasise the lesson, the students and I have placed a hardboiled egg into a jar of vinegar on Tuesday. We have also added a teaspoon of green food colouring since we have read "Green Eggs and Ham" (and the kids insisted that we make the egg turn green). The children and I observe the egg every day. On Wednesday, we have noticed that the eggshell has (mostly) been dissolved. By Friday, the eggshell is completely dissolved and all that's left is a green rubber egg. |
In a more scientific explanation, when you submerge an egg in vinegar, the shell dissolves. Vinegar contains acetic acid, which breaks apart the solid calcium carbonate crystals that make up the eggshell into their calcium and carbonate parts. The calcium ions float free (calcium ions are atoms that are missing electrons), while the carbonate goes to make carbon dioxide - the bubbles that we have seen.
Our teeth is similar to the eggshell because our teeth come into contact with different kinds of acids everyday (i.e. our saliva, the food that we eat, etc.). If we do not brush our teeth properly on a regular basis, we risk getting cavities because the acids can erode our teeth. Furthermore, stains (like the green food colouring) can become permanent.
To be honest, the children were more interested in the bouncing green rubber egg rather than my explanation on acids and teeth. However, sometimes...all that is needed is a little magic to spark understanding and learning. We will be coming back to this topic once more some time in the future.