Using Zinc and ammonium nitrate to start a fire with water
NOTE: THIS EXPERIMENT IS HIGHLY HAZARDOUS AND CAN RESULT IN INJURY OR DEATH. IT IS NOT INTENDED TO BE CONDUCTED BY CHILDREN BUT RATHER, IT SHOULD BE CONDUCTED BY SICENCE TEACHERS ONLY!
Zinc does not occur freely in nature but does exist in the ores of other metals. It was widely used centuries before people knew what it really was. For instance, Romans smelted copper ores that contained zinc to make weapons out of brass without even knowing it.
Zinc is one of the most used metals on the planet. Iron and steel pipes are dipped in molten zinc to produce a coating that protects the metals against corrosion –a process called galvanizing. Brass is 30 percent zinc and 70 percent copper. Zinc mixed with ammonium nitrate will ignite on contact with water and is used in survival kits as fire starting mechanism. In this experiment, we’ll demonstrate how water kicks off the exciting chemical reaction in a classic experiment known as “Negative X”.
- Place a fire-proof asbestos mat on a table.
- Mix 1 teaspoon of zinc dust with one half teaspoon of ammonium nitrate. Make sure both are dry and mix slowly (or the reaction may occur prematurely.
- Place a few grains of ammonium chloride and stir gently.
- Push a small depression on top of the pile of dust
- Put one drop of water in the depression and stand back. Note how the zinc ignites and flashes with a brilliant blue-white flame followed by a dense cloud of white smoke.
The addition of water promotes a chemical reaction that liberates ammonia, hydrochloric acid, water vapor, and nitrous oxide. Oxygen from the nitrous oxide ignites violently with the zinc forming the white zinc oxide.
Powdered zinc has an enormous surface area. When water is added, the zinc is ionized and creates a tremendous amount heat in the process. The ammonium nitrate is a strong oxidizing agent which accelerates the reaction and eventually causes the zinc to burn in air.
Note: zinc oxide itself is non-toxic, however it is hazardous to breathe zinc oxide fumes – it’s a poison gas which means, yeah, you can die if you breathe it!
Negative X experiment notes
A mixture of zinc powder, ammonium nitrate, and ammonium chloride is often called “Negative X.” Adding just a small drop of water initiates a redox reaction, which is sped up by the presence of chloride ions. Being a strong reducing agent, zinc reacts explosively with nitrate ions to produce zinc oxide, nitrogen, and water:
NH₄NO₃ + Zn = ZnO + N₂ + 2H₂O
This is a good example that demonstrates why water is not used to put out chemical fires.
Negative X Experiment Supplies
Supplies: Zinc Dust, Ammonium chloride, Ammonium nitrate
In-Article Image CreditsAn aluminothermic reaction with Iron(III) oxide; as known as a thermite reaction via Wikimedia Commons with usage type - Creative Commons License. March 30, 2010
Featured Image CreditAn aluminothermic reaction with Iron(III) oxide; as known as a thermite reaction via Wikimedia Commons with usage type - Creative Commons License. March 30, 2010