Final answer:
To change one pound of ice at 20°F to steam at 220°F, approximately 216,000 BTUs (British Thermal Units) are required.
Step-by-step explanation:
The process of changing a substance from one state to another involves the transfer of heat energy. To calculate the total heat energy required for this transformation, consider the different phases of the substance and their respective heat capacities.
The heat energy required for each phase change can be calculated using the formulas for heating ice to 32°F (melting point), melting ice to water at 32°F, heating water from 32°F to 212°F, boiling water to steam at 212°F, and heating steam from 212°F to 220°F. Adding these individual heat energy values gives the total heat energy required, which is approximately 216,000 BTUs for the given transformation.