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Finger Smoke
Think SAFETY with this one!!!!! Not too be done without
adults!
This week's experiment is one that I tried many years ago, when
I was a kid. At the time, I was impressed with the results, but now I am more
impressed with the chemistry behind the results. To try this, you will need:
We don't actually need the matches. What we want is the striker
strip on the package. Tear this strip off the package, and place it on the coin.
You don't want it to hang over the edge, so you will probably have to either
bend it or tear it in half.
Carefully, use a match or a lighter to set the strip on fire. If
you plan to use one of the safety matches, remember that you have just removed
the striker. When the strip has burned, carefully move it aside. On the coin,
you will see a brown, oily liquid. Rub your finger across it, to get the stuff
on your finger. Then rub your finger and thumb together. As they rub together,
you should see wisps of white smoke rising from them. The smoke will show up
better if you have plenty of light and a dark background.
Where is the smoke coming from? The striker for the safety
matches contains red phosphorus. When you burned the striker, the heat vaporized
some of the chemicals it contains. Some of the red phosphorus from the strip
condensed onto the cool metal. When red phosphorus combines with air, it
produces a white smoke. As you rubbed your finger and thumb together, you
exposed more of the red phosphorus to the air, producing more smoke.
BE SURE TO WASH YOUR HANDS IMMEDIATELY. These chemicals
can irritate your eyes. It is important to know that we are dealing with red
phosphorus. It comes in other forms, such as white phosphorus, which is very
poisonous.
So why do they call it red phosphorus if it looks brown and
oily? The brown, oily stuff is not the phosphorus. It is tar, condensed from the
smoke of the burning paper. When you hear about the tar in cigarette smoke, this
is what they are talking about. Imagine that brown, sticky stuff in your lungs,
instead of on your fingers. Now you know why I have never smoked a cigarette.
You can still see the tar if you burn a piece of the matchbook without the
striker, but in that case, it will not smoke when you rub it between your
fingers.
In our experiment, the phosphorus is mixed in with the tar. The
tar helps to keep the air away, so the phosphorus does not oxidize into smoke
too quickly. When you rub your fingers together, more of the phosphorus is
exposed, and you see the smoke.
Once again, be sure to wash you hands very well when you are
done. Safety is always important in science experiments. There are all sorts
of chemicals around us every day, and many of them can be harmful if they are
not used properly. The smoky smell on your fingers also messes up the taste of
ice cream, so do a good job of washing up.
Have a wonder filled week.
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