A ____ is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

• A. Btu
• B. Calorie
• C. Joule
• D. Watt

Answer: (A)

This question tests understanding of a heat-energy unit used with water. The term that fits the definition is the Btu, which stands for British thermal unit. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. This exact phrasing is what the statement describes, making it the best match.

For context, a calorie is the energy needed to raise one gram of water by one degree Celsius (much smaller and in metric units), and the joule is the SI unit of energy (with 1 Btu ≈ 1055 joules). A watt measures power, not total energy, so it isn’t the right unit for this definition.