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Name: Danielle
Status: student
Grade: 9-12
Location: Australia



Question:
I am doing an experiment involving the effects of various colas on teeth (I am using pig's teeth as human teeth were difficult to get). After being in the cola for 2 days, I weighed them and was surprised to find that they teeth weighed more than they did before they were put in. I was not sure if this was due to the fact that they had absorbed some of the liquid or because of the black coating on them or perhaps another reason I had not thought of?


Replies:
Hi Danielle,

I must say that the gain in weight is a bit strange. What percentage of weight gain was there? Is it possibly within experimental error? Possibly there is some water being absorbed into the spongy interior of the tooth. I suspect that unless the black deposit is relatively thick, it cannot materially add to the tooth's weight.

By the way, it is not the Cola (per se) that makes any difference to the teeth. It is only the amount of phosphoric acid that the cola contains (and colas strangely do contain this stuff!). Carbonic acid (caused by the CO2 being dissolved) will also corrode the tooth, but if the experiment goes on several days, the CO2 will be long gone (the cola will be "flat"), so only the phosphoric acid will be left as a corrosive agent.

Regards,
Bob Wilson.



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