Question

How many Joules of energy are required to change 10 gram of ice at -2 οC to water at 20 οC?

Answer 1

The total heat required to change 10 gram of ice at $-2^{\circ}\rm C$ to water at $20^{\circ}\rm C$ is given by

$$Q=Q_1+Q_2+Q_3$$

$$Q=c_{ice}m(0^{\circ}{\rm C}-(-2^{\circ}{\rm C}))+\lambda m+c_{water}m(20^{\circ}{\rm C}-0^{\circ}{\rm C})$$

$$Q=2100\times 0.01\times 2+334000\times 0.01+4200\times 0.01\times 20$$

$$=4222\:\rm J.$$