According to Hess's Law, what principle applies to enthalpy changes?

Hess's Law states that the overall enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps that make up the reaction, regardless of the path taken to go from reactants to products. This principle reflects the fact that enthalpy is a state function; it depends only on the initial and final states of a system, not on how it gets from one to the other.

This means that even if a reaction occurs through multiple steps or different intermediates, the total enthalpy change remains the same when considering all of these steps together. This concept is particularly useful in calculating enthalpy changes for reactions that cannot be measured directly or are difficult to measure experimentally.

The other options do not accurately capture Hess's Law. The first option implies that enthalpy changes can only be measured directly, which is not true since Hess's Law allows us to calculate them indirectly. The third option claims independence from temperature, which is misleading since enthalpy changes can be temperature-dependent. Lastly, stating that enthalpy changes are always negative is incorrect; enthalpy changes can be positive or negative depending on whether the reaction is exothermic or endothermic.