Question

CLASSIFY THE FOLLOWING AS PHYSICAL OR CHEMICAL CHANGES.GIVE REASONS FOR YOUR ANSWERS:

a.CUSTARD BEING PREPARED

b.CARBON BURNING IN AIR TO GIVE CARBON DIOXIDE.

c.BURNING OF PETROL.

Answer 1

a. Preparation of custard is a chemical change as the product formed, custard, cannot be changed back to the reactants, custard powder and milk.
b. Burning of carbon in air to form carbondioxide is a chemical change. Carbondioxide is the product formed is a gas and is composed of carbon and oxygen. It is different from carbon or air. Carbondioxide cannot be converted back to carbon.
c. Burning of petrol is a chemical change. Petrol burns in air to form carbondioxide and water which are chemical different products than petrol. Also, the process cannot be reversed.