Answer:
the sodium nitrate in this investigation is
a) the solute
b) undergoing chemical change
generally, solute is the substance which is added in solvent.
The substance which is taken in relatively more volume is the solvent.
so, here sodium nitrate (NaNO₃) is the solute which is dissolved in water (H₂O) , which is solvent.
The reaction between them is :
NaNO₃ + H₂O ⇒ Na⁺ (aq) + NO₃⁻ (aq) ; (aq) denotes aqueous;
so, here sodium nitrate undergoes chemical change into aqueous sodium ions(Na⁺) and aqueous nitrate ions(NO₃⁻).