Question

Classify the following in physical or chemical change.

Dissolving zinc metal in hydrochloric acid.

Answer 1

Chemical change: A permanent change in which new substances are formed whose chemical and physical properties are completely different from that those of the original substance.

• When we dissolve zinc (Zn) metal in hydrochloric acid (HCl) then chemical reaction takes place and new compound zinc chloride is formed along with hydrogen gas. Following chemical reaction take place.

$\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Zinc}\mathrm{chloride}}{{\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$

• Thus, dissolving zinc metal in hydrochloric acid forms the new substance zinc chloride which has properties different from the reactants.

Hence, it is a chemical change.