Characteristics of iron and its reaction with oxygen

How iron interacts with oxygen


Iron is a met­al of medi­um chem­i­cal ac­tiv­i­ty, which is present in many min­er­als: mag­netite, hematite, limonite, siderite and pyrite.

Specimen of limonite [Deposit Photos]

Chem­i­cal and phys­i­cal prop­er­ties of iron

In nor­mal con­di­tions and in pure form, iron is a sol­id sub­stance with a sil­very-grey col­or and a bright metal­lic shine. Iron is a good con­duc­tor of elec­tric­i­ty and heat, as can be test­ed by touch­ing an iron ob­ject in a cold room. As the met­al swift­ly con­ducts heat, in a short pe­ri­od of time iron takes most of the warmth from hu­man skin, and af­ter you touch it for a while it feels cold.

Pure iron chips with a high purity iron cube [Wikimedia]

The melt­ing tem­per­a­ture of iron is 1538 de­grees Cel­sius, and the boil­ing tem­per­a­ture is 2862 de­grees. The char­ac­ter­is­tic prop­er­ties of iron are good duc­til­i­ty and fusibil­i­ty.

Iron re­acts with sim­ple sub­stances: oxy­gen, halo­gens (bromine, io­dine, flu­o­rine and chlo­rine), phos­pho­rus and sul­fur. When iron is burnt, met­al ox­ides form. De­pend­ing on the con­di­tions of the re­ac­tion and the pro­por­tions be­tween the two par­tic­i­pants, iron ox­ides can dif­fer. The equa­tions of the re­ac­tions:

2Fe + O₂ = 2FeO;

4Fe + 3O₂ = 2Fe₂O₃;

3Fe + 2O₂ = Fe₃O₄.

These re­ac­tions take place at high tem­per­a­tures.

Here you’ll find out what chem­i­cal ex­per­i­ments with iron you can do at home.

The re­ac­tion of iron with oxy­gen

For iron to re­act with oxy­gen, it must be heat­ed be­fore­hand. Iron burns with a daz­zling flame, scat­ter­ing sparks – in­can­des­cent par­ti­cles of iron cin­der Fe₃O₄. The same re­ac­tion of iron and oxy­gen also takes place in air, when dur­ing me­chan­i­cal pro­cess­ing, steel heats up dras­ti­cal­ly from fric­tion.

[Deposit Photos]

When iron is burned in oxy­gen or in air, iron cin­der forms, the equa­tion re­ac­tion is:

3Fe + 2O₂ = Fe₃O₄, or

3Fe + 2O₂ = FeO • Fe₂O₃.

Iron cin­der is a com­pound in which iron has dif­fer­ent va­len­cies.

Ob­tain­ing iron ox­ides

Iron ox­ides are prod­ucts of re­ac­tion be­tween iron and oxy­gen. The best-known of them are FeO, Fe₂O₃ and Fe₃O₄.

Iron (III) ox­ide Fe₂O₃ is an or­ange-red pow­der, which forms on the ox­i­da­tion of iron in the air.


The sub­stance forms on the break­down of the salt of triva­lent iron in air at a high tem­per­a­ture. A lit­tle iron (III) sul­fate is placed in a ce­ram­ic bowl, and heat­ed over a gas burn­er. In the ther­mal break­down, iron sul­fate breaks down into sul­fur ox­ide and iron ox­ide.

Iron (II, III) ox­ide Fe₃O₄ forms on the com­bus­tion of pow­dered iron in oxy­gen or in the air. To ob­tain the ox­ide, a lit­tle fine iron pow­der is mixed in a ce­ram­ic pot with sodi­um ni­trate or potas­si­um ni­trate. The mix­ture is heat­ed over a gas burn­er. When potas­si­um and sodi­um ni­trate are heat­ed, they break down, with the re­lease of oxy­gen. Iron burns in oxy­gen, form­ing the ox­ide Fe₃O₄. Af­ter com­bus­tion ends, the ob­tained ox­ide re­mains on the bot­tom of the ce­ram­ic pot in the form of iron cin­der.

Warn­ing! Don’t try to re­peat these ex­per­i­ments with­out a pro­fes­sion­al su­per­vi­sion!

Iron (II) ox­ide FeO forms in the break­down of fer­ric ox­alate in an in­ert at­mos­phere, and is a black pow­der.