The Department of Chemistry at the University of Illinois
The Chemistry learning center
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.
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pours just the right amount of methanol into the jug.
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.
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.
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.