Sodium hydroxide (NaOH), commonly known as lye, dissolves in water and releases heat due to an exothermic reaction. This process involves the dissociation of NaOH into its constituent ions, Na+ and OH-, which then interact with water molecules. The heat released during this reaction is a result of the formation of new, stronger ionic bonds between the sodium and hydroxide ions and the water molecules.

The exothermic nature of the reaction can be attributed to the energy required to break the ionic bonds in NaOH and the energy released when new, stronger bonds are formed with water. The lattice energy of NaOH, which is the energy required to separate the ions in the solid, is higher than the energy released when these ions are surrounded by water molecules. This difference in energy results in the release of heat as the reaction progresses.

Experimental data support this phenomenon. For instance, the enthalpy change for the dissolution of NaOH in water is approximately -44.4 kJ/mol. This negative value indicates that the reaction is exothermic, as the energy released during the formation of new bonds is greater than the energy required to break the original ionic bonds.

The heat released during the dissolution of NaOH in water can be significant and is often utilized in various industrial processes, such as in the production of soap and paper. It is also important to note that the reaction can be hazardous, as it can cause burns due to the high temperature and the caustic nature of NaOH. Proper safety measures, such as wearing protective gloves and eyewear, are essential when handling sodium hydroxide.