What is the preferred SI unit for measuring heat, energy, or work?

The Joule is the preferred SI unit for measuring heat, energy, or work because the International System of Units (SI) defines the Joule as the standard unit of energy. One Joule is defined as the energy transferred when a force of one newton is applied over a distance of one meter. This alignment with the fundamental principles of physics and its application across various scientific disciplines make the Joule the most universally accepted and standardized unit.

Additionally, while other units like the calorie or BTU (British Thermal Unit) are commonly used in specific contexts, such as in chemistry or thermal engineering, they are not part of the SI system. The Watt, which is also mentioned, is a derived unit that represents power (the rate at which energy is transferred) and is equal to one Joule per second. Therefore, when discussing energy or heat specifically, the Joule takes precedence as the most appropriate and recognized unit within the SI framework.