Answer the following: 3 × 1 = 3 (a) Write two observations when green coloured crystals of ferrous sulphate are heated in a boiling tube. (b) Why…

Copper changes to copper (II) oxide which is black in colour./

\[\underset{\text { Brown }}{\mathbf{2 C u}(\mathbf{s})}+\mathbf{O}_{\mathbf{2}}(\mathbf{g}) \xrightarrow{\text { Heat }} \underset{\substack{\text { Copper(II) Oxide } \\ \text { (Black) }}}{\mathbf{2 C u O}(\mathbf{s})} \]

Calcium oxide (quick lime) and colourless gas \(\displaystyle \left(\mathrm{CO}_{2}\right)\) is evolved) /

\[\mathrm{CaCO}_{4}(\mathrm{~s}) \xrightarrow{\text { Heal }} \mathrm{CaO}[\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g}) \]