Methane demonstration

Methane reacts with oxygen according to the chemical equation below.

CH4(g) + 2O2(g) => CO2(g) + 2H2O(l)

When methane burns in oxygen, chemical energy is quickly converted into light and heat. Reactions that release energy are called exothermic reactions. This is a great demonstration when studying gases in junior science or exothermic reactions in senior chemistry.

 

Equipment:
- two litre plastic bottle
- scissors
- 40cm rubber tubing
- 15 cm glass tubing
- rubber stopper
- dishwashing detergent
- tripod
- a 1m broom handle
- small candle.
Cut the plastic bottle in half and insert the rubber stopper into the mouth of the bottle as shown on the right. Place the end of the rubber tubing over the nozzle of the gas outlet.
Prepare a concentrated solution of dishwashing detergent. Place no more than 2 cm3 of this solution inside the bottle and open the gas tap. Ensure that the gas pressure is sufficient so that soap solution does not go back down the glass tubing. Gas bubbles should now start to form.

 

 
Attach a small candle to the end of a long stick. A broom handle at least 1m long is recommended. This will be used to light the gas bubbles from a safe distance.

 
When sufficient bubbles have formed collect a handful of these bubbles and move well away from the gas source. Large bubbles should slowly rise when they are released. At this point ask for an adult assistant (not a student) to hold the stick with the burning candle and be ready to light the bubbles. Release the bubbles with a quick shake of the hand. As the bubbles rise ignite the gas with the candle.

 
View the video on the right.

Questions

Give two properties of methane gas as observed from the demonstration?
How do you know a chemical reaction took place?
Where did the light and heat energies come from?
Safety
Methane is highly flammable and no naked flames must be near the gas source. All steps must be taken to avoid accidental ignition. Gas bubbles should be ignited from a distance and goggles must be worn by those conducting the demonstration. The flames generated may spread beyond the size of the bubbles. No student should be allowed near the demonstration.

 

Senior chemistry worksheet