Why does lithium move on the surface of water during the reaction?
What happens when you put lithium (or sodium or potassium) in water? What is the chemical reaction that is occurring?

The alkali metals react with water to produce alkali hydroxides and hydrogen gas:

$$\ce{2Li(s) + 2H2O(l) -&gt; 2LiOH(aq) + H2(g)}$$

The two products of the reaction of water and lithium are lithium hydroxide (which dissolves) and hydrogen. Hydrogen is not very soluble in water, and it is much less dense than air. The motion of the lithium on the surface of the water is created by the escape of the hydrogen gas, which provides upward force.