Answer 1:
There are two forces at work in tooth decay
from soda. The first of these is, as you
mentioned, the carbonation. Carbonated
beverages contain carbon dioxide, or
CO2. Soda like Coca-Cola is made of
water (H20), flavored syrup, and
CO2. The
equation for carbonation is as follows:
H20+CO2--->H2CO3.
The right side of the equation
is carbonic acid. Tooth decay is caused by
acids dissolving the enamel of the teeth.
Now, you might worry that you have been
soaking your teeth in acid every time you take a
big gulp of soda, and you would be partially
correct. Since the carbonic acid that is formed
in the soda is dissolved in the water, it comes
into contact with your teeth for only a short time
every sip.
The second contributor to tooth decay
is sugar. Sugar from sodas (and fruit juices,
for that matter) coats the teeth every time you
take a sip. Bacteria in our mouths break down the
sugar into acids, similar to the equation above
for carbonic acid. However, since sugar is
sticky, it sticks to your teeth and therefore
provides a longer time of exposure to acids. That
is why sugar is usually the main culprit in
tooth decay.
Now, for your experiment. Since you want to
study only the effects of carbonation, you must
use that as your only variable (ask your science
teacher what this means if you are not sure). I
would suggest using a drink that contains only
carbonation, and no sugar. You also want it to be
clear so that you can see what is happening as it
happens. Therefore, use 'soda water' or 'seltzer,'
which is just CO2 in water. (You could
also vary the experiment by having lots of
different kinds of soda and checking the effects
of *sugar*, but that is a different
experiment.)The fizziness you experience when you
have a freshly opened can of soda is the carbon
dioxide 'escaping.' However, as the soda sits and
gets 'flat,' the carbon dioxide is turning into
carbonic acid.
If you fill a glass with fresh seltzer, it will
dissolve a tooth. However, unless you have lots
of baby teeth sitting around the house and your
parents are looking for a cool way to get rid of
them, I wouldn't suggest using teeth!Instead, take
a piece of limestone (which also has calcium in
it!), and drop it into the glass. As time wears
on, it will dissolve more and more. If you refill
the glass with fresh soda, it will dissolve slower
than if you just let the same glass sit and turn
flat. Why?
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