Iron pepper-shaker

"Pepper" a candle!

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

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Keep a bowl of water nearby when working with fire.
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

The iron powder extinguished the candle.

Most likely, you poured too much iron powder onto the flame. But this is definitely not a problem; just light the candle again and continue the experiment. This time, try to pour the iron powder in smaller portions by gently tapping the bottom of the bottle with a finger.

I can’t pour the iron powder.

Firstly, make sure there is powder left in the bottle. Since iron powder is rather fine, it can cling to the inside of the bottle. This way you might assume there is some powder inside when it has actually run out.

Another possible option is that some plastic melted and closed the bottle nose. This isn’t great; it means you brought the bottle too close to the fire. Please be careful not to do it again! Try to pierce the bottle nose with the unbent paper clip. If this doesn’t work, replace the damaged bottle nose with a new one - there is an extra in the experiment set.

The bottle nose doesn’t fit the bottle well.

Normally, you have to push the bottle nose hard to insert it completely. Check out how it holds: if it is already inserted securely, there is no need to keep trying.

The candle burnt down completely. How can I extract it from the stopper?

Just let the candle residue cool down a bit; 1-2 minutes should be enough. Use a wooden stick to push the candle residue out of the stopper.

Step-by-step instructions

Prepare the iron powder and the candle.

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It is very hard to set an ordinary piece of iron on fire. But tiny iron particles heat up quickly in the candle flame and burn easily.

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Expected result

Iron powder sparkles brightly in the candle flame.

Disposal

Dispose of solid waste together with household garbage.

Scientific description

Why do the sparkles appear?

When we sprinkle the iron powder over the candle flame, small particles of the powder catch fire, resulting in bright sparkles.

Why does the iron powder burn?

When iron is in the form of a powder, its particles are very fine and oxygen can easily reach all the iron atoms in each of the particles -- in contrast to the bulk metal, where most of the iron atoms are located inside the bulk where oxygen cannot reach them.

Learn more

It is easy to imagine burning wood or paper, but much harder to imagine burning iron, especially if we think of the bulk metal. And indeed, a solid piece of iron can incandesce when put in flame, but it will not ignite. Why do small pieces of iron ignite? Let’s study the chemistry of the experiment in more detail.

The main participant in almost any burning process is oxygen. Oxygen comprises about 21% of the volume of our air. To make iron burn, oxygen must be very close to the iron atoms. A particle of the powder is very fine, so lots of oxygen molecules in the air can surround this particle and ignite it under certain conditions (like heating, as in our experiment). In other words, the powder has a large surface area for the oxygen in the air to interact with, which significantly facilitates combustion.

Here is the chemical equation for this process:

Fe + O2 → Fe3O4 (or FeO ∙ Fe2O3)

The resulting product of this reaction is iron (II, III) oxide, which is actually a mixture of the two iron oxides: FeO and Fe2O3.

Regarding the bulk metal, oxygen can only reach the few iron atoms which are located on the surface of the bulk. The iron atoms inside the bulk have no contact with oxygen at all. Compared to the same weight of iron powder, bulk iron has very little contact with oxygen, limited to the surface of the bulk itself. The bulk metal, consequently, does not burn.

Moreover, bulk iron easily conducts heat, so when we try to ignite it, the bulk easily disperses the heat into the environment. However, the fine particles of the iron powder do not have enough volume to disperse the heat, so they have no recourse except to burn.

What if the iron powder were even finer than it is in the experiment?

In this case, the particles of the powder could ignite even without heat from the candle. The property of a powder to ignite in air without any impact is called pyrophoricity and such a powder is pyrophoric. Iron powder is a good example of a pyrophoric substance, but it’s not alone. For example, fine particles of nickel, uranium, and some other metals or their compounds can ignite spontaneously too. Even very fine and dry flour can suddenly catch fire, but of course, this is not a common occurrence that happens in ordinary home conditions.