One way to solve this problem is to look at the units of the heat capacity of water. The units are J/gK. Basically all you are doing in this problem is changing these units into the units Joules by multiplying the heat capacity by the grams of water and the change in temperature. It becomes a modified factor-label problem in this way except that you are using measured quantities rather than definitional conversions. This is the equivalent of solving it by algebra using the following relationship…heat change = specific heat x mass x change in temperature. You need to convert one liter of water to grams using density and figure out the change in temperature in degrees Kelvin. What are these values? J