For one pound of water at 32 degrees Fahrenheit, how many BTUs must be removed to create ice at 17 degrees?

To determine how many BTUs must be removed to convert one pound of water at 32 degrees Fahrenheit to ice at 17 degrees Fahrenheit, it's important to consider the specific heat of water, the heat of fusion, and the temperature differences involved.

Initially, when water is at 32 degrees Fahrenheit and needs to become ice, it must go through two primary processes:

1. Cooling the water from 32 degrees Fahrenheit to 0 degrees Fahrenheit:

The specific heat of water is approximately 1 BTU per pound per degree Fahrenheit. To lower the temperature from 32°F to 0°F, you subtract 32°F. Thus, the calculation would be:

[

32 \text{ degrees} \times 1 \text{ BTU/pound/°F} = 32 \text{ BTUs}

]

2. Converting the water at 0 degrees Fahrenheit to ice:

This process requires the heat of fusion, which is the amount of energy required to change water at its freezing point (0°F) into ice without changing its temperature. The heat of fusion for water is approximately 144 BTUs per pound.

3. **Cooling the ice from 0 degrees