Step 1: A chemical change forms a new substance and is generally permanent; a physical change only alters shape, state or appearance. Step 2: (i) Burning paper gives ash, CO₂ and water vapour – new substances → chemical change. Step 3: (ii) Melting wax is only a change of state; wax stays wax → physical change. Step 4: (iii) Milk to curd involves bacteria converting lactose into lactic acid – new substance → chemical change. Step 5: (iv) Salt dissolved in water can be recovered by evaporation → physical change. Step 6: Chemical changes = (i) and (iii) = 2. Answer: 2.