As the bright sun shines upon the water, the water slowly dissapears. This is an example of physical change because here the water is just transformed into water vapour. So only the state and the shape of the substance has changed. Its originality remains absolutely intact. In the second case where the same sunlight gives energy to the surrounding plants to convert water and carbon dioxide into sugar and oxygen gas, it is a chemical change. here new substances are formed and the identity of the original substances are lost.In chemical reactions, the mass of the product will always be the same as the mass of the reactants.
