If I increase the mass of magnesium powder added to a copper sulfate solution, will the temperature of the reaction rise? Why?

The temperature will rise.

Magnesium is more reactive than copper. Magnesium and copper sulfate solution undergo displacement reaction. The temperature will rise because the displacement reaction is exothermic. The equation is:
Mg(s) + CuSO₄(aq) → MgSO₄(aq) + Cu(s)
OR: Mg(s) + Cu²⁺(aq) → Mg²⁺(aq) + Cu(s)

Besides, copper ions act as the catalyst of the reaction between magnesium and water. This reaction is also exothermic. The equation is:
Mg(s) + 2H₂O(l) → Mg(OH)₂(s) + H₂(g) [Cu²⁺(aq) ions act as catalyst]