This week's experiment involves both chemistry and light.
You will need:
a candle
pliers or kitchen tongs
a penny (You can any coin, a nail, or other metal objects.)
a clear glass filled with water
In order to make the penny look silver, we first need to coat it with
a chemical known as carbon. Luckily, carbon is a very common
chemical. When you burn a piece of wood or paper, the black stuff
left behind is carbon. We will get our carbon from a burning candle.
Place the candle into a holder and carefully light it. Hold the penny
with the pliers and then move the penny into the candle flame. You
will quickly see that the coin turns black. This is carbon. You are
not burning the penny. The carbon is being produced by the burning
wax of the candle. It is collecting on the penny instead of burning
in the candle flame.
Coat the penny with a thick layer of carbon on both sides. DO NOT
TOUCH THE PENNY. IT IS HOT! Touching it will also rub off the carbon
and get your fingers dirty. Don't worry that the part of the penny in
the pliers is not covered with carbon. That part of the penny will
act as a control, to show you what the penny would look like without
the carbon.
Carefully, drop the penny into the glass of water. Looking down from
the top, nothing seems to have changed. Now, look at the penny
through the side of the glass. The black part of the penny is now
bright silver.
Did it really change colors? No, you can look down from the top again
to see that it is still the same. Why does it seem to be silver? The
thick layer of carbon traps and holds air. This forms a bubble around
the black part of the penny. When you are looking straight down, you
see through the air bubble easily. Looking from the side, the light
you see is hitting the bubble at an angle. It is reflected off of the
bubble, making it look silver. If you shake the glass gently, you
will see the silver bubble moving as the water moves.
When you finish, pour out the water and wash the penny (and your
hands.) The soft layer of carbon washes off the penny easily. It will
probably take some soap to get it off of your fingers.
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