The reaction between sodium and water is a chemical reaction because it involves the formation of new substances with different chemical properties than the original reactants. Here's a breakdown:

* Reactants: Sodium (Na) and water (H₂O)

* Products: Sodium hydroxide (NaOH) and hydrogen gas (H₂)

The key indicators of a chemical reaction:

1. Change in chemical composition: The sodium atoms react with water molecules, breaking and forming new bonds. This results in the formation of sodium hydroxide and hydrogen gas, which have different chemical compositions than the original sodium and water.

2. Energy change: The reaction is highly exothermic, releasing significant heat energy, evident in the vigorous bubbling and potential ignition of the hydrogen gas.

3. Production of new substances: The formation of sodium hydroxide and hydrogen gas are entirely new substances with distinct properties compared to the reactants. Sodium hydroxide is a strong base, while hydrogen gas is a flammable gas.

In summary: The reaction between sodium and water is a chemical reaction because it results in the formation of new substances with different chemical properties than the original reactants. This is accompanied by energy changes, indicating the breaking and forming of chemical bonds.