Here's why:

* Hydrochloric acid (HCl) is a strong acid when concentrated, meaning it completely ionizes in water, releasing all its hydrogen ions (H+).

* Dilution means adding more water to a solution. This decreases the concentration of the acid.

* While HCl is a strong acid in its concentrated form, its strength is reduced by dilution. The hydrogen ions are still released, but the concentration is much lower, making it act more like a weak acid.

It's important to note: Even a dilute solution of hydrochloric acid can be corrosive and dangerous. Always handle acids with caution and proper safety procedures.