What is a fundamental outcome of every chemical reaction?

In every chemical reaction, a fundamental outcome is the formation of at least one new substance. This process involves the rearrangement of atoms to create bonds in different configurations, leading to new chemical properties and characteristics that differ from the original substances. For instance, when hydrogen reacts with oxygen, they produce water, which is a distinct substance with unique properties compared to hydrogen and oxygen in their elemental forms.

The other options may occur in some reactions but are not universal. Energy absorption can happen, such as in endothermic reactions, but not all reactions absorb energy; some release it instead. Color changes and gas production are also common phenomena but do not happen in every reaction. For example, many reactions may occur without any visible color change or gas generation. Therefore, the formation of new substances is the only characteristic that is consistent across all chemical reactions, making it the most fundamental outcome.