Ammonium nitrate is a fairly safe chemical that has some interesting properties. The reaction that happens when ammonium nitrate is added to water serves as a useful demonstration of an endothermic reaction. The end products of the reaction between ammonium nitrate and water are also easily disposed of after an experiment, and can be used as a fertilizer.
Ammonium nitrate is a salt of ammonium and nitric acid, and its chemical composition is NH4NO3, or an ammonium and a nitrate ion. This substance is a colorless crystalline solid. It is typically used as a fertilizer, as the nitrogen in this compound is easily used by plants. It is also used as an explosive or in pyrotechnics. While fairly stable under ordinary circumstances, heating ammonium nitrate can have an explosive effect.
Water is a liquid at room temperature and consists of one atom of oxygen and two atoms of hydrogen per molecule of water. Water molecules are polar; that is, one part of the molecule has a positive charge and another part has a negative charge. The polarity of water gives it some unique properties; it can dissolve many different substances, particularly ionic crystals, like salt. Ammonium nitrate is one of the many substances that dissolves into ions readily in water.
While the chemicals that go into a reaction and those that are formed by a reaction are the most obvious components of a chemical reaction, heat is another factor in a chemical reaction. Exothermic reactions are reactions that release heat as a product, and exothermic reactions are typically more familiar than endothermic reactions. Endothermic reactions are reactions that take up heat during the reaction process, and the products of an endothermic reaction feel cold.
When ammonium nitrate is dissolved in water, it breaks down into its ions: ammonium and nitrate. The reaction of ammonium nitrate dissolving is unusual in that it is endothermic and dissolved ammonium nitrate will feel cool for some time. Neither the water nor ammonium nitrate are changed in any other way other than the ammonium nitrate is dissolved. However, when aqueous or dissolved ammonium nitrate is heated, the solution breaks down to release nitrous oxide, or laughing gas.