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We did the experiment at school. We dissolved anhyrous copper sulphate and hydrous copper sulphate, measured the energy changes and did an energy cycle, but my results did not quite turn out right.

Is this a valid area for error:

Anhydrous CuSO4 is in an unstable state and when exposed to moisture, will move to the more stable CuSO4.5H2O, causing a release of energy. This was seen when the grey substance was placed in the water and immediately turned blue, while an increase in temperature was measure. However, once the CuSO4 had become hydrated, the blue crystals sat on the bottom of the cup, where they would have begun to dissolve. This would be identical to the first reaction measured, and would have caused an endothermic enthalpy change. Thus, the temperature curve for the temperature change of CuSO4 must be less than expected. 



Also, is there any other systematic errors which could account for measuring a higher enthalpy than the the theoretical value?
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