What is the difference between a chemical reaction and a physical change?
A chemical reaction is a process in which substances are chemically transformed into new substances. This change is characterized by a change in the chemical composition of the substance, and is often accompanied by the release or absorption of energy. A physical change, on the other hand, is a process in which a substance changes its physical properties, such as size, shape, or state, without undergoing a change in its chemical composition. Physical changes include processes such as melting, freezing, boiling, and condensation.
In summary, a chemical reaction results in a new substance, a change in chemical composition and a change in energy, while a physical change results in a change in physical properties, but no change in chemical composition, no new substance and no change in energy.