An open container holds 0.550 kg of ice at - 15.0o C. The mass of the container can be ignored. Heat is supplied to the container at the constant rate of 800.0 J/min for 500.0 min. (a) After how many minutes does the ice start to ?melt?? (b) After how many minutes, from the time when the heating is first started, does the temperature begin to rise above 0.0o C? (c) Plot a curve showing the temperature as a function of the elapsed time.

Solution 50 Step 1: The expression for heat required for the ice to raise the temperature to 0 C is Q = mcT Q = mc(T 2 ) 1 The ice starts melting when temperature reaches 0 C . Where 0 Q heat required for the ice to raise 0 C m mass of ice (m = 0.550 kg) 3 C specific heat of melting ice (C = 2.10 × 10 J/kg.k) T 1 initial temperature of system (T = (115 + 273 K)) T final temperature of system (T = 273 K) 1 2