Steel wool

So you think iron doesn’t burn?

Difficulty:
Danger:
Duration:
10 minutes
Experiment's video preview

Reagents

Safety

  • Put protective eyewear on.
  • Conduct the experiment on the plastic tray.
  • Keep a bowl of water nearby during the experiment.
  • Place the burner on the cork hot pot stand. Do not touch the burner after the experiment - wait until it cools down.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

Steel wool just wouldn’t ignite. Why?

First, check whether the batteries are inserted correctly into the holder. Perhaps, the batteries are old, and the remaining charge on them is insufficient to start the reaction. Simply replace the batteries with new ones.

Second, double-check all the wire connections. Third, try fluffing up the steel wool a little more—probably, there isn’t enough oxygen in there to support burning of iron. After checking all of these points, try touching the crocodile clips to the steel wool one more time.

Step-by-step instructions

Iron wool consists of thin iron threads that air can pass through easily. To make this process even easier, fluff up the piece of iron wool.

iron_wool_en_iks-01

When electric current passes through a conductor (such as an iron wire), the conductor heats up. If the wire is thick enough, this effect is almost unnoticeable. But since iron wool threads are very thin, they become red-hot.

iron_wool_en_iks-02

The red-hot iron readily reacts with oxygen in the air, i.e. burns.

iron_wool_en_iks-03

Disposal

Dispose of solid waste together with household garbage.

Scientific description

Why does the steel wool burn?

People used to think that iron and its alloys do not burn, unlike wood or paper. Think of movies about knights - when they bring a sword into a flame, it glows, incandescent with heat but it doesn’t burn. In contrast, dry wood is easily ignited with just a little spark. Yet, with the right technique and under controlled conditions, iron will burn in seconds – just like a sheet of paper!

Iron flammability (i.e. its ability to burn) depends on its configuration. Very fine iron filings are pyrophoric: meaning that they easily ignite when heated or held to a flame. The difference between iron filings and an actual sword is in the surface area. The surface area of the filings is by far much larger than that of an intact, solid piece of iron with the same mass. Therefore, it is much easier for oxygen to reach the iron in the filings, and as a result, their oxidation proceeds much faster. This rapid reaction is involved in burning.

Although steel wool has a smaller surface area than the iron filings, it is still much larger than that of a single solid piece of steel with the same mass. In order to ignite a piece of steel wool, we must pass electricity through it. This is almost the same process that takes place in an incandescent light bulb. Due to the electrical current, the wire in the light bulb is heated, however, it doesn’t burn because there is almost no oxygen in the lamp. When electricity passes through steel wool, the wool, just like the wire, begins to glow white hot with intense heat. However, it quickly burns because it is exposed to the oxygen in the air.

What substance is formed?

In our experiment, steel wool transforms into ferrous ferric oxide Fe3O4, or FeO•Fe2O3. This compound is also called magnetite. It is heavier than iron and features high electrical conductivity and magnetic properties.

The reaction equation is as follows:

3Fe + 2O2 → Fe3O4

Besides oxygen, steel wool also reacts with other oxidizers, such as chlorine and potassium chlorate.