What does 1 BTU represent in terms of water temperature change?

One British Thermal Unit (BTU) represents the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. This quantity is a standard measurement used in heating and cooling systems, particularly in refrigeration and HVAC applications, to quantify energy transfer.

In this context, when considering the options, recognizing that one BTU specifically correlates to a one-degree temperature increase in one pound of water is essential for understanding thermal energy transfer. This definition allows professionals in the field to apply this knowledge when calculating heating or cooling loads, determining energy efficiency, or troubleshooting refrigeration systems.

The other options either refer to wrong measurement units (like gallons or liters) or incorrectly state the temperature change per unit of mass (such as a change of 2 degrees or referring to a gallon instead of a pound), thereby failing to correctly represent the definition of a BTU.