|MadSci Network: Biochemistry|
First, sorry for taking so long, but things in the lab have been very busy. I will start by saying that, depending on what equipment you have available to you, this might be too complicated for a 5th grade science project.
I know that both the eggs (if you hard-boil an egg and then soak it in vinegar, you can make a really cool display item by pushing the egg into a bottle with an opening that normally would be too small for the egg, but once you soak it in vinegar it becomes rubbery and will compress through an opening that is "too small") and the chicken bones will become soft, and I am not sure if the teeth will become soft (seems unlikely) or brittle (seems more likely, since eggshells and bones are already slightly malleable, but teeth really are not).
The only way I can think of determining if the acid has drawn calcium out of these materials would be try to form calcium carbonate (limestone). This will be hard with materials that you might have available, but here is what I would try. After you have soaked these items in your various liquids, pour off the liquid into a separate container. Now pour out an equal amount of that same liquid (in other words, if you poured 100 mLs of lemon juice off of your soaking eggs, in a separate container pour 100 mLs of fresh lemon juice) into a separate container, and to each of these containers slowly add baking soda, and keep stirring both continually (you may need a helper for this). The hope would be that the bicarbonate from the baking soda would combine with any calcium from the eggs or teeth or bones, and the calcium carbonate that forms is insoluble and would precipitate out. The reason you need the container of fresh solution is that, since you are adding baking soda to the liquid, at some point you will add too much baking soda and it will no longer dissolve. By having the other container (your "control" reaction), you are observing the difference in the behavior of baking soda in lemon juice, with the only difference being that there is one additional variable: the presence of the residue from your soaking of something in one of the juices (this is the way all scientific experiments are done: to change one variable at a time and see what the effect is). So really the only thing you can do here is say that, by soaking something in the lemon juice, you get precipitate faster than if you don't soak something in it, and that faster formation is probably due to the presence of calcium carbonate, or limestone.
Let me know how this goes, and feel free to email my directly if you have any further questions.
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