The flaming flask is an interesting experiment that shows how removing the protective layer causes the aluminium to react with air.

In this experiment we mix copper chloride and hydrochloric acid and pour it on aluminium strips and ignite them. This is a violent chemical reaction, procedure to be done with precautions.

Safety First! Adult supervision required. Wear protective eye wear and clothing. Don’t eat/drink your experiments.

Materials and tools required

Chemicals:

  • Copper Chloride – 10 gm
  • Hydrochloric Acid (50 ml concentrated)
  • Aluminium Foil

Apparatus

  • 1000 ml Conical Flask
  • 100 ml Measuring Beaker
  • Long Lighter

Video on the YouTube for experiment

What to do!

Step 1 – Take some stripes of Aluminium foil and fold them.

Step 2 – Put the folded stripes of Aluminium foil in the conical flask.

Step 3 – Mix 50 ml hydrochloric acid with 10 gm copper chloride in a measuring beaker.

Step 4 – Put the mixture into the conical flask.

Step 5 – Immediately light a splint with a long lighter.

Step 6 – Switch of the light and watch the blue dancing flame.

Images for instructions

Working principle of the activity

This activity follows two chemical reaction which helps in this beautiful outcome. One is the reaction of aluminium with copper chloride and the other one is the reaction of aluminium with hydrochloric acid.

2Al(s) + 3CuCl2(aq) → 2AlCl3(aq) + 3Cu(s)

2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)

The aluminium oxide layer protects the metal beneath from further reaction with air, water or acid. But chloride ions can ligate aluminium ions at the metal–oxide interface and break down the protective layer, allowing the reaction to proceed.

Adding the copper chloride-hydrochloric acid mixture to the foil in the flask will begin to react vigorously and produce hydrogen gas. Hold the lit splint by the opening of the flask and the gas will ignite. If you have timed it right, the flame will sink back into the flask and dance inside.

Safety Precautions

  • Hydrochloric acid is a very strong chemical.Perform this experiment under adult supervision.
  • In addition to performing the project on a heat-safe surface, it’s a good idea to do it in a well-ventilated area, under a fume hood, or outdoors. There may be a small amount of smoke.
  • Do not add fuel to the fire while it is still burning. Wait until the flames are extinguished and then add more mixture and re-light the fire.
  • It’s a good idea to wear protective eye wear and clothing, as for any science demonstration. Avoid wearing synthetic fabrics, as they readily melt if exposed to flame. Cotton, silk, and wool are good choices, or you can wear a lab coat.