This week's experiment comes from my neighbors at the Malibu Creek State Park
campground. While taking my morning walk, I heard a lady bragging to her husband that he started the campfire with only one match. That made me think of the fellow that I watched the night before as he poured two bottles of
charcoal lighter fluid onto a pile of wood and still failed to get the fire
going. He would pour on the liquid and get a huge blaze, which quickly died. How could the heat of one match work better than a gallon of blazing lighter fluid?
To find out, you will need:
an adult (Any time you are working with fire, you should have another adult with you, even if you are an adult yourself.)
a wooden pencil or a stick about the same size
a wooden toothpick
a bowl of water
Place the candle on a flat surface or in a holder, so it will stay upright. Instead of using matches, we will use the candle as an easier and safer heat source. Next we will need some wood for our campfire. Lets begin with the pencil. Look carefully to be sure that it is really made of wood.
Recently, I found some that were plastic. That would not work well at all for
experiment. Holding the end with the eraser, put the other end into the candle
flame. Watch to see how long it takes for the pencil to catch fire so that
it will burn on its own, without the candle flame. Once it is burning, dip
the end in the bowl of water to put it out.
Next lets try the same procedure using the toothpick. Once it is burning,
drop it into the bowl of water. Did you notice a difference? The pointed
end of the toothpick should have caught fire much faster. Why?
First, it is smaller, so it takes less heat energy to raise its temperature
to the point where it will burn. The lady that started her fire with only one
match knew to begin with small pieces of wood. Once they are burning, you
can use their heat energy to heat larger pieces of wood. By going in steps
from small to large, you can soon have a large log burning on your fire.
Second, for our fire to burn, we need to get plenty of oxygen to the wood.
If there is not enough oxygen, then the wood will not burn, even if it is very
hot. With a large piece of wood, the oxygen is on the outside, but there is
a lot of wood on the inside that the oxygen can't get to. With a bundle of
small sticks, oxygen and heat can get to the pieces on the inside, letting
bundle of small sticks burn much faster than a large log. The better air
can flow through your campfire, the better it will burn.
Does that mean that you should not put large pieces of wood on your campfire?
No. Once it is going, you want it to last for a while. That is where
the log comes in. The same things that make it hard to get the log burning
will make sure that it burns slowly, making your fire last long enough to cook
your supper and still have plenty of heat for toasting marshmallows later.
But what about the fellow with the lighter fluid? Why didn't all of that
flame start his fire? Take a close look at the burning candle. Watch the
wick carefully. Is it burning? At first, it would seem that the answer is
yes, but as you watch, you will see that even though the candle burns, the
is lasting a very long time. What you are actually burning is the wax from
the candle. The heat melts the wax, which then soaks into the wick. This
liquid wax climbs up the wick in the same way that water climbs up a paper
when you are cleaning up a spill. As the liquid wax gets closer to the
flame, it is heated enough to break down into gases which will burn. As long
there is plenty of wax, the wick does not burn at all. When the wax melts
down enough, the liquid wax will not be able to climb all the way to the top
the wick. Then the end of the wick burns away.
The lighter fluid was doing the same thing as the liquid wax. It made nice
flames, but as long as there was plenty of lighter fluid, the wood did not
burn. The majority of the heat was moving upwards, away from the wood.
Because he was using large pieces of wood, the last bit of heat as the fluid
was not enough to set the wood on fire. He could have fixed this by placing
small pieces of wood on top of his fire, so that the heat of the big flame
would get them hot enough to burn. Then he could have used that heat to start
larger pieces of wood. It would have been much easier and safer for him to
skip the lighter fluid and build his fire correctly. Besides, toasted
marshmallows taste much better without the kerosene taste of the lighter fluid.
From Robert Krampf's Science Education Company
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