Which energy value represents melting one pound of ice into water?

Which energy value represents melting one pound of ice into water?

• A. 144 BTUs
• B. 10 BTUs
• C. 970 BTUs
• D. 60 BTUs

Answer: (A)

Melting ice into water at 0°C requires latent heat of fusion—the energy used to change a substance from solid to liquid without raising its temperature. For ice, this value is about 333.55 kJ/kg, which converts to roughly 144 BTU per pound. So melting one pound of ice uses about 144 BTUs of energy. The other numbers don’t fit because they correspond to different processes: a much smaller amount would not overcome the molecular bonds to melt, and a value around 970 BTU is the latent heat of vaporization (energy to turn water into steam), not melting.

Melting ice into water at 0°C requires latent heat of fusion—the energy used to change a substance from solid to liquid without raising its temperature. For ice, this value is about 333.55 kJ/kg, which converts to roughly 144 BTU per pound. So melting one pound of ice uses about 144 BTUs of energy. The other numbers don’t fit because they correspond to different processes: a much smaller amount would not overcome the molecular bonds to melt, and a value around 970 BTU is the latent heat of vaporization (energy to turn water into steam), not melting.