Question

When sodium hydroxide dissolves in water is it a chemical or physical change?

Answer 1

Sodium hydroxide is a compound with molecular formula of $NaOH$ , it can dissociate into ions in presence of water. Each mole of sodium hydroxide can dissociate into one mole of sodium and one mole of hydroxide ion. As new bonds are formed, the process can be known as a chemical change.

Complete answer:
Chemical compounds are classified into three types based on the nature of these compounds. They are acidic, basic and neutral compounds.
Basic compounds generally contain lone pairs of electrons or a hydroxide ion. Sodium hydroxide is a base with the molecular formula of $NaOH$ . It can easily abstract a proton from other compounds.
Sodium hydroxide consists of sodium and hydroxide groups. In presence of water, it can dissociate into ions namely sodium ion and hydroxide ion. The chemical dissociation will be as follows:
$NaOH \rightleftharpoons N{a^ + } + O{H^ - }$
When sodium hydroxide dissolves in water the bond between the sodium and hydroxide breaks leads to the formation of ions. Any reaction associated with the breaking of bonds and leads to new products is known as chemical change.
Thus, sodium hydroxide dissolves in water as a chemical change.

Note:
There are two types of changes in chemical reactions which are physical change and chemical change. Chemical change is associated with the difference in chemical composition. Physical change does not associate with the change in chemical composition, one of the examples for physical change is melting of ice.