* Physical Change: The initial process of dissolving is physical. The NaOH crystals break down into smaller particles and disperse throughout the water. This is a change in state and appearance, but not in the chemical composition of the NaOH.
* Chemical Change: However, once dissolved, NaOH undergoes a chemical reaction with water. This is an exothermic reaction, meaning it releases heat. The reaction forms hydroxide ions (OH-) and sodium ions (Na+). This is a chemical change because the chemical composition of the substance changes.
In summary:
* Dissolving NaOH in water involves an initial physical change (dissolution) that is followed by a chemical change (reaction with water).
