What happens when a piece of aluminium metal is added to dilute hydrochloric acid?

Aluminium and dilute HCl react to produce an aqueous and gaseous byproduct. Aluminium reacts with dilute $HCl$at room temperature. The metal dissolves in $HCl$, to give aluminium chloride and colourless hydrogen gas. 
This reaction is found to be irreversible since the final products will not react with each other. An oxidation-reduction reaction occurs when metallic aluminium and hydrochloric acid are combined. 

Aluminium reacts with an acid to generate aluminium salt and gaseous hydrogen in a typical single displacement reaction.
Hence, the addition of aluminium metal to dilute $HCl$ produces hydrogen gas.