Question

what is the total number of joules released when a 5.00 gram sample of water changes from liquid to solid at 0°C ?

Answer 1

The heat associated with a change of physical state of a system is: $Q = m\cdot l$ (being "l" the latent heat of state change).

$Q = 5\ g\cdot 334\frac{J}{g} = \bf 1,67\cdot 10^{3}\ J$