No, a chemical reaction does not always result in the formation of a new substance. Chemical reactions involve the rearrangement of atoms, molecules, or ions to form different combinations, but the outcome can vary.
Formation of New Substances: In many cases, chemical reactions do lead to the creation of new substances with different chemical properties. Bonds between atoms are broken and new bonds are formed, resulting in the production of molecules or compounds that differ from the original reactants. This is commonly observed in reactions such as combustion, oxidation, and synthesis reactions.
No Change in Composition: In some instances, chemical reactions may occur without any change in the chemical composition of the substances involved. These reactions are referred to as physical changes. For example, dissolving a substance in water or changing the physical state of a substance (such as melting, freezing, or boiling) are processes that involve intermolecular forces and do not alter the chemical identity of the substances.
Equilibrium: Some reactions reach a state of equilibrium where the forward and reverse reactions occur at equal rates. In this case, although the reactants are constantly transforming into products and vice versa, there is no net change in the overall composition of the system.
It's important to note that the definition of a "new substance" depends on the level of specificity. At the atomic and molecular level, rearrangement of atoms leads to new substances. However, at a macroscopic level, some changes may not appear to produce new substances if the properties being considered do not significantly differ from the original substances.
In summary, while many chemical reactions do result in the formation of new substances, some reactions may not lead to a change in composition or may reach an equilibrium state where the overall composition remains constant.