A chemical reaction is generally accompanied by certain external indications or characteristics. These include – change of – (a) colour (b) state (c) smell (d) evolution of gas (e) formation of precipitate (f) evolution or absorption of heat. With reference to change of colour – state the change in colour seen when the following are heated – copper carbonate.
Change of colour — In certain chemical reactions a change of colour is seen to be observed. Heat on substances to observe change in colour of reactants and products.
Copper carbonate CuCO3 → CuO + CO2[g]
Copper carbon [CuCO3] – Green – to Copper [III] oxide [CuO] – Black