In physics, how is energy typically expressed according to the first law of thermodynamics?

Energy is typically expressed as something that can change forms in accordance with the first law of thermodynamics, which is also known as the law of energy conservation. This principle states that energy cannot be created or destroyed; it can only be transformed from one form to another. For example, chemical energy in a fuel can be converted into thermal energy during combustion, or kinetic energy can be transformed into potential energy and vice versa. This ability of energy to change from one form to another is crucial in understanding various physical processes and interactions in the universe.

The other options do not accurately reflect the essence of the first law of thermodynamics, as they suggest static or unchanging views of energy, which overlooks the dynamic nature of energy transformations in physical systems.