Vapor Phase Oxidation - Ignition of Alcohol Vapor

Brief Description: 

A small amount of ethanol is placed in a bottle having electrodes through its sides. When a Tesla coil is touched to one of the electrodes, a spark is produced within the bottle and the ethanol explodes, popping the cork from the bottle.

Purpose/Goal: 

This demonstration is suitable when discussing combustion reactions in general, as well as properties of organic chemicals, or to illustrate the conversion of chemical energy to mechanical energy.

Explanation of Experiment: 

A small amount of ethanol liquid is placed in a bottle containing air. Some of the ethanol vaporizes, producing an explosive mixture of vapor and oxygen. When a spark is created, the mixture detonates. The resulting combustion reaction is exothermic, and it produces carbon dioxide and water vapor at high temperature:

C2H5OH (g) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g)

The production of hot gases causes the pressure inside the bottle to increase suddenly. This pressure increase expels the cork from the neck of the bottle. A blue flame leaps from the mouth of the bottle after the cork is ejected.

Materials Preparation: 
  • 2-3 mL 95% ethanol, C2H5OH
  • Nails or brazing rods, cut to appropriate lengths
  • Polyethylene plastic bottles – 125, 250, 500, 1000 mL
  • Corks to fit bottles
  • Thumbtacks
  • Party ribbons
  • Tesla coil

Construct a reactor by inserting a nail through the side of the plastic bottle until its tip is near the center of the bottle. Insert the other nail through the opposite side of the bottle so its tip is about 0.5 cm from the tip of the first nail. Pour 2 mL of 95% ethanol into the bottle. Stopper the bottle with the cork, and attach the party ribbon to the top of the cork with a thumbtack – this assists in relocation of the cork after the demonstration. Set the bottle in an area free of overhead obstruction.

Presentation: 

Turn on the Tesla coil and bring its tip to one of the nails. A spark will jump to the nail and from one nail to the other. The spark inside the bottle detonates the mixture of air and ethanol vapor, causing the cork to shoot out of the bottle.

Hazards: 

Care should be taken to avoid damage to light fixtures or other objects because the cork is expelled with considerable force. Ethanol is highly flammable – a fire extinguisher should be ready when the demonstration is presented.

Disposal: 

Any remaining liquids should be poured into a suitable container for waste solvents or flushed down the drain with water.

Video: 

General Concept:

Primary Reference: 
Shakhashiri, Bassam Z., Chemical Demonstrations – A Handbook for Teachers of Chemistry – Volume 2 p 216.