I need ho design an experiment on the dissolution of NH4NO3 in water. My independent variable is the amount of solvent (water) while my dependent variable will be the difference in temperature before and after the reaction. What could the hypothesis and scientific reasoning be?

Answer 1

<<The energy needed to break the bonds between the ammonium and nitrate ions is greater than the energy evolved between the ammonium and nitrate ions and the water molecules>> so temps go down.
I dont recommend this as a experiment, as you are relating temp vs how much water has been added...First, if say you had some solution, the temp went down to to XXC. Then you added more water..at another temp...the temp will change for two factors: one, you diluted the solution, but more importantly, you added water at another temperature. You will have no way to separate the effects, and certainly no scientific reasoning.

What you can do, is make the independent variable the amount of ammonium nitrate added, and then measure temp change.
Hypothesis: temp goes down because of what I cited in the <> above.