Final answer:
To change five pounds of ice at 20°F to steam at 220°F, 1720 BTUs of heat are required.
Step-by-step explanation:
To calculate the amount of heat required, we need to consider two processes: first, the heat required to raise the temperature of the ice from 20°F to its melting point, and second, the heat required to convert the ice at its melting point to steam at 220°F.
The heat required to raise the temperature of the ice can be calculated using the specific heat capacity of ice, which is 0.50 BTU/lb·°F. So, the heat required for this process would be: 5 lb × 0.50 BTU/lb·°F × (32°F - 20°F) = 60 BTU.
The heat required for the phase change from ice to water is given by the equation: heat = mass × heat of fusion. The heat of fusion for ice is 144 BTU/lb. So, the heat required for this process would be: 5 lb × 144 BTU/lb = 720 BTU.
Finally, to calculate the heat required to raise the temperature of the water from the melting point to steam at 220°F, we use the specific heat capacity of water, which is 1 BTU/lb·°F. So, the heat required for this process would be: 5 lb × 1 BTU/lb·°F × (220°F - 32°F) = 940 BTU.
Adding up the heat required for each process, we get the total amount of heat required: 60 BTU + 720 BTU + 940 BTU = 1720 BTU.