Question

What is the amount of heat required to change 2kg of ice at -15°c to water at 70°c ( C=4200jkg-¹k-¹

Answer 1

Given:

$m=2\:\rm kg$

$c_{ice}=2100\:\rm J/(kg\cdot K)$

$c_{water}=4200\:\rm J/(kg\cdot K)$

$\lambda=330\:000\:\rm J/(kg)$

The total amount of heat

$$Q=Q_1+Q_2+Q_3$$

$$Q=c_{ice}m(0^\circ C-(-15^\circ C))+m\lambda\\ +c_{water}m(70^\circ C-0^\circ C)$$

$$Q=2100*2*15+2*330\:000 +4200*2*70\\ =1311000\:\rm J$$