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Alcohol, Water and Cloth Burning
Name: Pammy S.
Status: student
Age: 11
Location: N/A
Country: N/A
Date: 7/15/2004
Question:
Why is it that when you try to burn a cloth that was
immersed in a mixture of alcohol and water, the cloth does not burn?
What kind of chemical reaction takes place here?
Replies:
This not an experiment I would recommend because IT COULD CATCH FIRE. For
combustion to occur three factors must co-exist: Fuel (here alcohol and
cloth), oxygen (from the air), and ignition source(to get the fuel hot
enough to produce a self-sustaining flame). In a mixture of alcohol and
water, IF THERE IS ENOUGH WATER PRESENT there will not be a sufficient ignition
source. HOWEVER, THE ALCOHOL VAPOR ABOVE THE CLOTH could contain sufficient
alcohol vapor to ignite, and THAT IS THE UNEXPECTED DANGER.
Alcohol vapor can "flash" that is burn very rapidly -- not quite an
explosion -- but a "WOOOSH" that can expand several feet in a fraction of a
second. You could get seriously burned by this flash. I do not want to
discourage your scientific interest, but this is really a very risky
experiment to be trying.
Vince Calder
Pammy,
This is a marginally dangerous experiment inasmuch as its safety depends on a
careful balance between the water and alcohol content. Done properly, it works
because water has a great heat capacity -- that is, it can absorb a lot of heat
without changing much in temperature. When the alcohol/water soaked cloth is
ignited, the heat of alcohol's burning is partially absorbed by the warming and
vaporization of the water. This keeps the overall temperature to a bearable level
during which time the cloth will not burn and can be (sometimes) carefully handled
while aflame. In general, I think the experiment is to risky to be worthwhile. A
mistake can lead to serious burns or a fire. My advice: Don't do it.
Regards,
ProfHoff 876
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