(a) zinc carbonate, copper carbonate and lead carbonate :
On heating zinc carbonate, light amorphous white solid changes to pale yellow.
On heating copper carbonate, light green amorphous powder changes to black.
On heating lead carbonate, heavy white crystalline solid crumbles with a crackling sound.
(b) zinc nitrate and copper nitrate :
On heating zinc nitrate, white solid changes to yellow when hot and white when cold.
On heating copper nitrate, bluish green crystalline solid melts to form a bluish green mass and gives off steamy vapours which condense on cooler parts of the test tube.
On further heating, the bluish green mass changes to a black residue.
(c) copper sulphate and copper carbonate :
On heating copper sulphate, blue crystalline solid crumbles to form a white amorphous powder and gives off steamy vapours which condense on cooler parts of the test tube to form a colourless liquid (water).
On strong heating, a black solid is formed and a gas is evolved that turns moist blue litmus red and changes the colour of acidified K2Cr2O7 solution from orange to green suggesting that it is SO2.
On strongly heating copper carbonate, light green amorphous powder changes to black and a colourless odourless gas is evolved that extinguishes a burning wooden splinter and turns lime water milky but has no effect on acidified K2Cr2O7 solution suggesting that it is CO2.
(d) ammonium chloride and iodine :
On heating ammonium chloride, white crystalline solid sublimates to form a basic gas (NH3) and acidic gas (HCl). The dense white fumes are noticed that form a white mass on the cooler parts of the test tube.
On heating iodine, violet crystalline solid sublimates to form violet vapours. These vapours settle down on cooler parts of test tube to form violet crystals.