#Na^+# and #Cl^-# are present in solution as their aquated ions, i.e. #[Na(OH_2)_6]^+# and #[Cl(H_2O)_(4-6)]^-# (of course, the water ligands are quite labile). Because this ionization clearly involves the formation of new substances, and the making and breaking of strong chemical bonds, this is a CLEAR example of #"chemical change."#