Final answer:
When ammonium nitrate (NH4NO3) is dissolved in water, it absorbs heat, causing the solution to cool, which is termed an endothermic process. This is utilized in instant ice packs for treating injuries, where adiabatic cooling provides relief by reducing swelling without heat exchange with the environment.
Step-by-step explanation:
Temperature Change When Ammonium Nitrate is Dissolved in Water
When ammonium nitrate (NH4NO3) is dissolved in water, it results in a temperature decrease of the solution. This phenomenon is the basis for the functionality of instant ice packs, which are commonly used for treating injuries. The process of dissolving ammonium nitrate in water is endothermic, meaning that it absorbs heat from the surroundings. This can be demonstrated in an experiment where 3.21 g of solid NH4NO3 is added to 50.0 g of water, causing the temperature to fall from 24.9 °C to 20.3 °C, indicating that the dissolution absorbs thermal energy.
The endothermic dissolution of ammonium nitrate is interesting because it requires more energy to break apart the solute molecules than the energy released when they are surrounded by water molecules (solvent). Despite this, the dissolution process is spontaneous due to the increase in disorder, or entropy, within the system. This property is exploited in medical applications and the making of instant ice packs to provide adiabatic cooling when applied to injuries, as no heat is exchanged with the environment during the dissolution process within the pack.