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What evidence shows that sodium reacting with water is a chemical change?

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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.

The reaction between sodium and water is a definitive example of a chemical reaction because it results in the formation of entirely new substances, rather than merely changing the physical state of the original materials.12

Evidence of this chemical change includes:

Formation of New Substances: The constituent atoms of the reactants—sodium metal (Na) and water ( $H_{2} O$ )—are rearranged to create different products: sodium hydroxide (NaOH) and hydrogen gas ( $H_{2}$ ).13
Energy Release: The process is highly exothermic, meaning it releases a significant amount of heat.43
Electron Transfer: This specific process is an oxidation-reduction reaction, where electrons are transferred from sodium atoms to water molecules, fundamentally altering the chemical identity of the reactants.3

The reaction is represented by the following chemical equation:
$2 N a (s) + 2 H_{2} O (l) \to 2 N a^{+} (a q) + 2 O H^{-} (a q) + H_{2} (g)$ 3

Unlike a physical change, where a substance retains its chemical identity, this process demonstrates a permanent transformation of the starting materials into new chemical compounds.12