"Liquid Nitrogen vs. Sparkler" experiment

A fas­ci­nat­ing ex­per­i­ment with liq­uid ni­tro­gen!

Reagents and equip­ment:

• liq­uid ni­tro­gen;
• match­es;
• test tube;
• wa­ter;
• sparklers;
• beaker;
• flask.

Step-by-step in­struc­tions

Low­er a test tube of wa­ter, burn­ing match­es and burn­ing sparklers into liq­uid ni­tro­gen.

Pro­cess­es de­scrip­tion

In nor­mal con­di­tions, ni­tro­gen is a col­or­less in­ert gas, with­out taste, smell or col­or. If it is cooled to -196 °C, it turns to a liq­uid state. If you low­er a test tube of wa­ter into liq­uid ni­tro­gen, the wa­ter in­side the test tube freezes, but only the part that is im­mersed in the ni­tro­gen. As we know, ni­tro­gen does not sup­port com­bus­tion – the burn­ing match­es go out in its at­mos­phere. But why don’t the sparklers go out? Sparklers con­tain mag­ne­sium as fuel, bar­i­um ni­trate as an ox­i­diz­er, and also iron fil­ings to make sparks. In air, the chem­istry of the com­bus­tion process of sparklers can be shown by the fol­low­ing equa­tions:

Mg + O₂ → MgO

Mg + N₂ → Mg₃N₂

Fe + O₂ → Fe₃O₄ + Fe₂O₃

2Ba(NO₃)₂ → BaO + 4NO₂ + O₂

As mag­ne­sium is an ac­tive met­al, when it burns in air, mag­ne­sium ni­trate Mg₃N₂ forms – the prod­uct of its in­ter­ac­tion with the ni­tro­gen in the air, but very lit­tle of this prod­uct is formed. When sparklers burn in ni­tro­gen, the chem­i­cal process can be writ­ten as fol­lows:

Mg + N₂ → Mg₃N₂

Mg + O₂ → MgO

2Ba(NO₃)₂ → BaO + 4NO₂ + O₂

The ox­i­diz­ers in this case are ni­tro­gen and bar­i­um ni­trate. Prac­ti­cal­ly all the mag­ne­sium goes to form mag­ne­sium ni­tride, but in the break­down of bar­i­um ni­trate, oxy­gen forms, which also ox­i­dizes the mag­ne­sium, but the prod­uct of their in­ter­ac­tion forms in a very small quan­ti­ty.

Safe­ty pre­cau­tions

Con­duct this ex­per­i­ment wear­ing pro­tec­tive gloves and glass­es, in a well-ven­ti­lat­ed room. Ob­serve safe­ty rules with liq­uid ni­tro­gen.

Warn­ing! Only un­der pro­fes­sion­al su­per­vi­sion.