Cork Rockets: The Combustion of Methanol

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Page ID: 221934

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Chemical Concepts Demonstrated

Exothermicity
Liquids that expand when forming gases
Effects of sparks on combustible gases and volatile liquids

Demonstration

5 bottles containing about 1 mL of methanol are connected together by copper wires.
Touch the nail on the end of the row of bottles with the tesla coil.
Repeat.

Observations

The corks at the top of the bottles fly into the air when initially "sparked." When the bottles are corked and sparked again, the rockets no longer launch. When the bottles are tipped over and placed upright again, the corks launch again.

Explanation (including important chemical equations)

This reaction is initiated with a spark:

2 CH₃OH(l) + 3 O₂(g) -> 2 CO₂(g) + 4 H₂O(g)

At any given temperature, gases occupy a volume that is about 800 times larger than the corresponding liquid (even moreso in this case because of the additional moles produced). The reaction produces enough pressure very quickly to cause the corks to shoot off like rockets.

When the second attempt is made, there is too much CO₂and not enough O₂in the bottles to initiate the reaction.

When the bottles are tipped over, CO₂pours out and O₂comes back in, allowing the reaction to run again.

Contributors

Dr. George Bodner (Perdue University)