Chemical Physical Changes

Chemical Physical Changes Chemical and physical changes are related to chemical and physical properties. Chemical Changes Chemical changes take place at the molecular level. A chemical change produces a new substance.  Another way to think of it is that a chemical change accompanies a chemical reaction.  Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water. Physical Changes Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance, although the starting and ending materials may look very different from each other. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle. How to Tell Chemical Physical Changes Apart A chemical change makes a substance that wasnt there before. There may be clues that a chemical reaction took places, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.