A cold pack contains a mixture of chemicals, whose reaction creates cold (Myers, 2003). The chemical reaction that creates cold is an endothermic reaction. This reaction absorbs heat from the surroundings, leaving air and objects to be extremely cold. Because a cold pack is useful for refrigerators to keep temperatures extremely low, it is necessary to use those chemicals that do not act as a threat to the environment (Myers, 2003). The most suitable chemical for a cold pack is ammonium nitrate that is a potentially explosive and toxic chemical if ingested. Cold packs contain distilled water that should be mixed with ammonium nitrate for an endothermic reaction. The inner linings of a cold pack breaks for distilled water and ammonium chloride to mix and react with the absorption of heat from surroundings (Myers, 2003).
When ammonium nitrate mixes with water, it splits into negative nitrate ions and positive ammonium ions. Water molecules contribute to this chemical reaction significantly by donating their energy (Myers, 2003). The chemical equation for the reaction between distilled water and ammonium nitrate is as follows:
This reaction absorbs heat from the environment in Joules, which makes the solution extremely cold. A chemist can determine the amount of heat energy that this equation involves by using the following equation.
In which q is energy in Joules, c is the heat capacity, m is the mass of solution, T1 is the initial temperature in degrees Celsius, and T2 is the temperature when ammonium nitrate dissolves in distilled water.
Therefore, the reaction between ammonium nitrate and distilled water is an endothermic reaction. This reaction is useful for refrigerators because it maintains cold for about an hour even without power. However, ammonium nitrate is a toxic and explosive substance, and people must take care to avoid injection (Myers, 2003). A chemist can calculate the amount of heat energy involved in the chemical reaction.