How much BTUs is required to melt one pound of ice at 32 F?

How much BTUs is required to melt one pound of ice at 32 F?

• A. 144 BTUs
• B. 32 BTUs
• C. 1 BTU
• D. 0 BTUs

Answer: (A)

When ice is at its melting point, the energy you add goes into changing its phase from solid to liquid rather than raising its temperature. This is the latent heat of fusion. For ice, the latent heat of fusion is about 334 kJ per kilogram, which converts to roughly 144 BTU per pound. So melting one pound of ice at 32°F requires about 144 BTUs of energy. The other numbers don’t fit this fixed energy needed for the phase change: far less energy would only raise temperature or do nothing, and the energy to raise the melted water’s temperature is handled separately (about 1 BTU per pound for each degree Fahrenheit).

When ice is at its melting point, the energy you add goes into changing its phase from solid to liquid rather than raising its temperature. This is the latent heat of fusion. For ice, the latent heat of fusion is about 334 kJ per kilogram, which converts to roughly 144 BTU per pound. So melting one pound of ice at 32°F requires about 144 BTUs of energy. The other numbers don’t fit this fixed energy needed for the phase change: far less energy would only raise temperature or do nothing, and the energy to raise the melted water’s temperature is handled separately (about 1 BTU per pound for each degree Fahrenheit).