Final answer:
Alkali metals react with water to produce hydrogen gas and a metal hydroxide, with the reaction being rapid and exothermic.
Step-by-step explanation:
Metals, especially alkali metals, can react rapidly and exothermically with water to form hydrogen gas and a basic solution of the metal hydroxide. Alkali metals such as lithium (Li), sodium (Na), and potassium (K) are known for their high reactivity with water. For example, lithium reacts with water to produce hydrogen gas as follows:
2Li(s) + 2H₂O(l) → 2LiOH(aq) + H₂(g)
Another example is the reaction of sodium with water:
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
This type of reaction demonstrates that these metals displace hydrogen from water due to their ability to be oxidized more readily than hydrogen. As the reactions proceed, the hydrogen gas is released and, in some cases, the heat generated can be sufficient to ignite the hydrogen.