Sodium hydroxide (NaOH) dissolves in water and releases heat due to an exothermic reaction. This process is known as hydration and involves the dissociation of sodium hydroxide into sodium ions (Na+) and hydroxide ions (OH-) in the aqueous solution. The heat released during this reaction is a result of the formation of strong ionic bonds between the sodium and hydroxide ions and the water molecules.

The dissolution of sodium hydroxide in water is highly exothermic, with a heat of solution of approximately -442 kJ/mol. This means that for every mole of sodium hydroxide that dissolves, 442 kJ of heat is released into the surroundings. The strong ionic bonds between the sodium and hydroxide ions are broken, and new bonds are formed between the ions and the water molecules. The formation of these new bonds is more energetically favorable than the breaking of the original bonds, resulting in the release of heat.

The exothermic nature of this reaction can be attributed to the high lattice energy of sodium hydroxide. Lattice energy is the energy required to separate one mole of an ionic solid into its constituent ions in the gas phase. Sodium hydroxide has a high lattice energy due to the strong electrostatic attraction between the positively charged sodium ions and the negatively charged hydroxide ions. When sodium hydroxide dissolves in water, the lattice energy is overcome, and the ions are separated, allowing for the formation of new bonds with water molecules.

The hydration of sodium ions is particularly exothermic. Sodium ions are small and highly charged, which makes them highly polarizing. When sodium ions are surrounded by water molecules, the water molecules align themselves around the ion, forming a solvation shell. This solvation process is highly exothermic due to the strong electrostatic interactions between the sodium ion and the water molecules.

In summary, sodium hydroxide dissolves in water and releases heat due to an exothermic reaction involving the dissociation of sodium hydroxide into sodium and hydroxide ions, followed by the formation of new bonds with water molecules. The high lattice energy of sodium hydroxide and the strong solvation of sodium ions contribute to the exothermic nature of this reaction.