What does the first law of thermodynamics state?

The first law of thermodynamics, often referred to as the law of energy conservation, states that energy can only be transformed from one form to another, but it cannot be created or destroyed in an isolated system. This principle underlies numerous scientific concepts, indicating that the total energy of a closed system remains constant over time.

For instance, when chemical energy is converted into thermal energy during combustion, the total amount of energy before and after the reaction remains equal, even though it is present in different forms. This law is fundamental in fields such as physics and chemistry, as it helps scientists understand energy flow in various processes.

This understanding clarifies why the other choices do not accurately represent the first law. The notion that energy can be created or destroyed contradicts this law, as does the claim that energy is always quantifiable in all processes, which may be true in theory but not practically applied in every scenario. While energy is indeed constant in a closed system, the more precise statement is that it is transformed between forms rather than merely remaining constant.