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Physical Change
- occurs when one or more physical properties of a substance are changed but without any change in the substance's chemical properties or composition
- no new substance is formed
- all changes of phase are physical changes (from solid to liquid to gas)
Chemical Change
- is any change that results in the production of one or more substances that differ in chemical properties and composition from the original substances
- examples are the rusting of iron, the souring of milk, the burning of paper
Changes in Energy
- every change, either physical or chemical, involves an energy change
- generally the energy changes that accompany physical changes are not as noticeable as those that accompany chemical changes
- 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."