Hey guys...having some trouble with this, wondering if you can help me out!

The reaction between 0.0245g of magnesium with an excess of water was carried out in an ice calorimeter as used in this lab. The volume of water in the calorimeter decreased by 0.19mL during the reaction.

b) Calculate the enthalpy of the reaction (in KJ/mol) Show all steps of the calculation

....so I know that we get 0.0010 mol of Mg.. but how do we know what the energy in joules lost is?? We can't use the q=mc(deltaT) equation because we don't have temperature...??

Help?

Thanks......