How much energy does it take to raise 1 lb of water 1 degree, in BTU?

The amount of energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit is precisely defined as 1 British Thermal Unit (BTU). This unit of measurement is commonly used in heating and energy contexts, particularly in the fields of thermodynamics and HVAC (heating, ventilation, and air conditioning).

Understanding the utility of BTU is essential, as it quantifies the energy needed for temperature changes in water—a crucial element in various applications including heating systems and energy efficiency assessments.

Other choices, such as 5 BTU, 10 BTU, or 2 BTU, do not accurately reflect this standard measurement and would imply an incorrect understanding of the energy requirements for heating water. Therefore, the correct and widely accepted answer is that it takes exactly 1 BTU to raise 1 pound of water by 1 degree Fahrenheit.