Physical and Chemical Changes
Two types of changes take place during the formation of compounds and mixtures. A compound is formed as a result of chemical reaction while a mixture is formed only by mixing the constituents without any chemical reaction.
• Physical change involves a change in physical state, size and appearance of a substance.
• No new substances are formed.
• Change is temporary and can be reversed.
• No change in the mass or composition of constituents.
• Not much gain or loss of energy occurs.
Examples- Dissolving salt or sugar in water, sublimation of iodine, bending a glass tube, etc.
The change in which new substances are formed in a chemical reaction by interacting with other is called a chemical change.
• A chemical change is a permanent change and can not be reversed to give back substances in original structure.
• The original substances lose their identities and properties.
• Energy changes occur in a chemical reaction.
• The change in mass and composition takes place. Examples- Burning of magnesium in air, rusting of iron, digestion of food, baking of cake, burning of hydrogen in air or oxygen to give water, burning of fuels, ripening of fruits, etc.