Challengers Zone Learning

DEFINITION OF PHYSICAL AND CHEMICAL CHANGE.
Physical and chemical changes

Physical changes: - these are changes in the physical properties (size, shape, density) or state of matter without a change in composition. No new substances are formed during physical changes. As water changes from liquid to ice, its appearance changes but its chemical composition remains the same. If we heat platinum wire in a burner flame, the wire will become red hot. It returns to its original; silvery metallic form after cooling. The platinum undergoes a physical change while under the flame but its composition remains the same under both conditions.

Chemical changes: - these are changes to the chemical composition of a product and a new substance is formed with entirely different composition from the original material. If a clean copper wire is heated in a burner flame, a change in appearance is noted when it cools. The copper no longer has its characteristic color, but now appears black. The black material is copper ii oxide.