"Dazzling Flame" experiment

How magnesium burns in the water vapor

This looks like a very sim­ple ex­per­i­ment, but it con­ceals many in­ter­est­ing chem­i­cal pro­cess­es.

Reagents and equip­ment:

  • mag­ne­sium strip;

  • hot wa­ter;

  • phe­nolph­thalein so­lu­tion;

  • beaker;

  • spir­it burn­er;

  • tweez­ers;

  • lighter or match­es.

Step-by-step in­struc­tions

Burn the mag­ne­sium strip in the flame of the spir­it burn­er and dip it into the glass of hot wa­ter.

Pro­cess­es de­scrip­tion

Mag­ne­sium is an ac­tive met­al, but its sur­face is cov­ered with a durable ox­ide film. On heat­ing this film dis­in­te­grates and the mag­ne­sium burns with a blind­ing white flame. The met­al burns with the for­ma­tion of mag­ne­sium ox­ide and ni­tride. In the wa­ter va­por the mag­ne­sium burns even more strong­ly, as mag­ne­sium forces the hy­dro­gen out of wa­ter, the re­leased hy­dro­gen ig­nites, and the flame in­ten­si­fies. Mag­ne­sium hy­drox­ide forms, a weak base which turns the wa­ter con­tain­ing phe­nolph­thalein a pink col­or. Also, the mag­ne­sium ni­tride that is formed in the burn­ing process hy­drolyzes, with the for­ma­tion of mag­ne­sium hy­drox­ide and am­mo­ni­um. When am­mo­ni­um dis­solves in the wa­ter con­tain­ing phe­nolph­thalein it also turns it pink.

2Mg + O₂ → 2MgO

3Mg + N₂ → Mg₃N₂

Mg + H₂O → MgO + Н₂

Mg + 2H₂O → Mg(OH)₂ + Н₂

MgO + H₂O → Mg(OH)₂

Mg₃N₂ + 6H₂O → 3Mg(OH)₂ + 2NH₃

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves and glass­es. Use tweez­ers when light­ing the mag­ne­sium. You should look at burn­ing mag­ne­sium through dark glass­es, as there is a risk of re­ceiv­ing a burn to the reti­na and go­ing blind.

Warn­ing! Sub­stances of this ex­per­i­ment are tox­ic and high­ly dan­ger­ous for your health. Do not try this at home. Only un­der pro­fes­sion­al su­per­vi­sion.