What unit is used to measure the amount of heat needed to raise 1 pound of water by 1°F?

The British Thermal Unit (BTU) is a unit that is specifically defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit (°F). This measurement is very practical in the context of heating and cooling systems, making it a common standard in the United States for energy consumption and efficiency discussions.

In contrast, the joule is a unit of energy in the International System of Units (SI) and is not directly tied to the measurement of heat in the context of water temperature changes. The calorie, while related to heat, has a slightly different definition, measuring the heat required to raise the temperature of one gram of water by one degree Celsius. The Kelvin is a unit of temperature measurement in the SI system and does not measure heat energy.

The specificity of BTU for water and the imperial measurement system underlines its relevance in fire investigation contexts, where understanding the energy transfer related to materials and their states is crucial.