J.R. S. answered 04/22/20
Ph.D. University Professor with 10+ years Tutoring Experience
Looks like the experiment was to heat the copper and drop it into water and record the temperature change. Assuming that is the case, we can approach the problem as follows:
heat lost by copper = heat gained by water
heat lost by copper = q = mC∆T
q = (17.920 g)(CCu)(28.21)
heat gained by water = q = mC∆T
q = (60 g)(4.184 J/g/deg)(0.78 deg) = 195.8 J Since this is the heat gained by water it must be the heat lost by the copper. Thus...
195.8 J = (17.920 g)(CCu)(28.21 deg)
CCu = 195.8 J/(17.920)(28.21)
CCu = 0.387 J/g/º = specific heat of copper