Physical and Chemical Changes 

Every substance has a certain property like –

Physical Properties: A physical property of a substance means its shape, size and physical state of a substance. For example: when water boils it turns to vapor but its still water in gaseous form. Although its state changes.

Chemical Properties: The basic inherent nature of a substance is known as chemical properties. For example mold on a piece of bread. Once yeast is formed, we would never get the original bread form.

What are the physical changes?

• Physical changes are the changes in physical properties which does not involve new produce of substances.  Changes are very much reversible like – melting of ice.

Nature of a Physical change –

• Physical changes are mostly reversible
• Physical properties of a substance only changes not its chemical properties
• New substance is not created in this process

Wax melting: This is a reversible change because wax solidifies in room temperature. There is no new substance formed. No gas emissions and chemical property of wax does not change.

Cooking vegetables: This involves baking or frying of food which then cannot be brought back to the original self. Smell is produced. It’s a new substance altogether.

Digestion is an example of chemical change. New substances are produced. Food is broken down. Energy is released, cannot be converted to food again.

Weathering of rocks: Rock formation involves immense heat and pressure. Running water on them, intense wind and expansion as a result of heat. These changes are irreversible.