Probably just something like this.
Remember that specific heat capacity is is
the measure of the heat
energy required to increase the temperature of a unit quantity of a substance by a
certain temperature interval. So c = Q/mT. Q is heat
energy
Use the electrical components to heat up the water, assuming
that all electrical energy is converted to heat energy to heat up a
specific mass of water. Remember that E = IVt (current through
heating element x voltage of power source x time taken) Use
thermometer to see when the temperature of the water go up by lets
say 10 degrees.
So you got everything already lor. Then sub in and find. To have
more exact answer, just do multiple times and take
average.