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How do chemical reactions differ from physical changes such as melting ice?

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combustion — chemical reaction Log burning in a fire. Burning wood is an example of a chemical reaction in which wood in the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash.

Chemical reactions differ from physical changes because they involve a fundamental transformation of substances, whereas physical changes do not.

In a chemical reaction, the constituent atoms of the reactants are rearranged to create entirely new substances as products. This process requires breaking existing chemical bonds and forming new ones.12

In contrast, a physical change—such as ice melting into liquid water or evaporating into vapor—alters only the physical state or properties of a substance, while its chemical identity remains unchanged. Regardless of whether water exists as a solid, liquid, or gas, its molecule remains composed of the same two hydrogen atoms and one oxygen atom. While physical changes are influenced by interparticle forces that dictate the state of matter, they do not result in the formation of new chemical species.13