When solid ${\mathrm{CuSO}}_4$ dissolves in water to make a 1 M solution, the temperature of the system increases. When solid ${\mathrm{NH}}_4{\mathrm{NO}}_3$ dissolves in water to make a 1 M solution, the temperature of the system decreases. Which statement(s) must be correct for these dissolving processes?

(P) $\mathrm{\Delta }{H}^{\circ }$ values for both processes have the same sign.

(Q) $\mathrm{\Delta }{G}^{\circ }$ values for both processes have the same sign.