PhysicalAndChemicalChanges

1. occurs when one or more physical properties of a substance are changed but without any change in the substance's chemical properties or composition
2. no new substance is formed
3. all changes of phase are physical changes (from solid to liquid to gas)

Chemical Change

1. is any change that results in the production of one or more substances that differ in chemical properties and composition from the original substances
2. examples are the rusting of iron, the souring of milk, the burning of paper

Changes in Energy

1. every change, either physical or chemical, involves an energy change
2. generally the energy changes that accompany physical changes are not as noticeable as those that accompany chemical changes
3. energy can be released (exothermic) or consumed (endothermic) during the reaction

IMPORTANT: Lavoisier's principle of the Law of Conservation of Mass states that "matter cannot be created or destroyed by a chemical change."