Cesium metal is a highly reactive alkali metal that reacts explosively with water to produce cesium hydroxide (CsOH) and hydrogen gas (H2). This reaction is a classic example of a chemical change, as the starting materials (cesium metal and water) are transformed into new substances with different chemical properties (cesium hydroxide and hydrogen gas).

The chemical equation for this reaction is:

2Cs (s) + 2H2O (l) → 2CsOH (aq) + H2 (g)