Answer 1:
Scientists don’t usually do experiments to
prove that things happen. They usually do
experiments to try to support their explanations
of why they happen. These may sound like the
same thing at first, so let’s think about that
some more.
Let’s say you notice that gum loses its
flavor after you chew it for a while. You may
want to do some research about how long it
takes, and whether it takes the same amount of
time for all people, or all flavors, or all
brands. You’re not really trying to prove that
it does lose its flavor, you’re just trying to
get more information about flavor loss in
gum.
Now for the more interesting question, why
does gum lose its flavor when we chew it? We
may have a few different guesses or hypotheses.
Maybe being crushed by teeth breaks down the
flavor. Maybe the water in our saliva (spit)
breaks down the flavor. Maybe the water in our
saliva washes away the flavor and we swallow
it. Maybe enzymes (digestive chemicals) in our
saliva break down the flavor.
We can test these hypotheses with
experiments. For example, if being crushed by
teeth breaks down flavor, I can just crush gum
and test whether its flavor is gone. I can use
my earlier tests to see how long I should crush
it. If gum lost its flavor after 5 minutes of
chewing, five minutes of crushing with a hammer
should do the same thing. At least, it should
if my crushing idea is right. If the gum still
has flavor after five minutes of crushing, I
know that crushing is not the answer. It may
still be part of an answer, but I would need to
do more testing to find out. I never really
prove I was right, I can just say that my
hypothesis is a good explanation for all the
facts I know so far.
Let’s get back to your question. You already
know that food looks a lot different coming out
of our bodies than it does going in. So you
know that digestion occurs. Testing how is not
easy. Only people with a lot of training can do
experiments on actual people because experiments
can be dangerous. They have to go through a
strict process to show that their experiments
are safe and important.
You can experiment on the first step of
digestion by having it happen outside your
body. Starch is the stuff in flour, potatoes,
and foods like that. Starch is actually long
chains of sugars. Enzymes are chemicals that
speed up reactions. One of the enzymes
(amylase) speeds up the breakdown of starch into
sugar. This starts to happen right in your
mouth. You can test how this happens by using
your own spit. Remember, all of the testing
happens OUTSIDE your body. You are NOT putting
anything IN your mouth.
Go to this site:
click here and
print off the first 2 pages. You will need the
help of your biology or chemistry teacher to get
a solution to test for starch and to make sure
that you do things safely. Think about
different questions you could ask. Will water
by itself break the starch down into sugar? Is
the smashing part of chewing enough to break
down the starch into sugar? Does smashing
help? What else could you ask? When you design
an experiment, make sure that it’s a fair one.
For example, you wouldn’t test water that was
cold against spit that was warm because then two
things are different between your samples
(temperature and enzymes). You only want one
thing to be different.
Write back if you have any questions.
Thanks for asking,
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