4.	The temperature increase doesn’t match the temperature increase due to the fact that there is a limiting reagent and if the mass of Zn exceeds 1.2g the CuSO4 becomes the limiting reagent. To put that into perspective, the reaction with any mass of zinc greater than 1.2g will have the same number of reacting particles (thus same amount of thermal energy) as the reaction with 1.2g of zinc. It is not linear because as we get closer to the equilibrium mass 1.2g, the change in change in temperature decreases (secondary difference decreases). Thus it theoretically assumes the shape of an upside down parabola. The slope in this case would be the heat produced per gram. The slope decreases as mass increases (in other words the heat produced per gram decreases as mass increases) is because when you have less mass it takes less time to react than when you have more mass. Thus as such the reaction happens in a shorter period for lower masses of zinc, the change in temperature would be significant. Now consider having more mass; the reaction takes longer period time to finish. And this period allows the solution to cool a bit. Thus the secondary difference of change in temperature would decrease as mass goes up.