(a) Chemical reaction between iron and copper sulphate. When iron is added to blue colour solution of copper sulphate, it changes its colour to green due to formation of iron sulphate.

Copper Sulphate solution (blue) + Iron —> Iron Sulphate solution (green) + Copper (brown deposit)

(b) Reaction between acetic acid and baking soda. When vinegar (acetic acid) is mixed with baking soda, chemical reaction takes place and bubbles of carbon dioxide gas are formed along with some other substances.

Vinegar (Acetic acid) + Baking soda (Sodium hydrogen carbonate) —> Carbon dioxide + other substances

(c) Explosion of fireworks produces heat, light, sound. Explosion of firework is a chemical change.