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Methanol
vapor burning in a plastic jug
Why does the combustion
of methanol produce such a large flame?
Methanol has the formula
CH3OH. It is similar to methane, CH4, except a hydrogen
has been replaced with -OH. Methanol is very flammable and is sometimes
used as an additive in gasoline.
Click on the small
pictures to view the video. The file will open in a new browser window.
Video
for Windows |
Quicktime
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The jug is rolled
in order to increase the surface area of the liquid methanol. An
increased surface area speeds up the rate of vaporization. The vapor
pressure of methanol is higher than that of water, so the liquid
methanol enters the gaseous phase faster than water would if it
were poured into the jug at the same temperature.
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Video
for Windows |
Quicktime
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The reaction
takes place in the gaseous phase. In the presence of oxygen from
the air, the methanol gas burns when ignited with a flame. This
produces carbon dioxide and water. The intensity of the reaction
is dependent upon the concentration of methanol gas.
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This demo should
only be performed using a plastic jug. The large quantities of gases
(H2O and CO2) produced during the very rapid
combustion could easily shatter a glass container.
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