In our daily life, we encounter many changes in our surroundings, though we do not notice them, such as souring of milk, rusting of iron, stretching of a rubber band, bread becoming toast, melting of wax, liting of a match, etc. All these changes that take place around us are physical change or chemical change. Physical changes are the changes that change the physical traits of the substance, without making any change in their internal structure.

Definition of Physical Change

Physical change is a process in which the substance experiences change in its physical properties like shape, size, colour, volume, appearance, state (i.e. solid, liquid, gas), etc., that, without making any change in their molecular composition. These changes are volatile in; that can be reversed using simple physical methods.

The same element or compound exists prior, or after change, i.e. original characteristics of the object remain unchanged. For example,Melting of wax, boiling of water, dissolving sugar in water, chopping wood, crumpling of paper, etc.

Definition of Chemical Change

Chemical Change is defined as the process in which the atoms of one or more substances are rearranged or combined to form a new substance. When a substance undergoes chemical change, the chemical properties of the substance changes and it is transformed into a different substance with different chemical composition. Evolution of energy, the formation of bubbles, change in odour, change in temperature are some signs of chemical change.

Alternately, known as chemical reaction, wherein the substances involved are known as reactants, and the outcome of the reaction is called product. Energy change is one of the characteristics of a chemical change, because of the formation of the new product. Once the chemical change takes place, it cannot be reversed. For example, adding vinegar to baking soda, bleaching a stain, fermenting of grapes, etc.

physical changes are reversible while chemical changes are irreversible