Examples of Physical Changes

Physical changes involve states of matter and energy. No new substance is created during a physical change, although the matter takes a different form. The size, shape, and color of matter may change. Physical changes occur when substances are mixed but dont chemically react. How to Identify a Physical Change One way to identify a physical change is that such a change may be reversible, especially a phase change. For example, if you freeze water into an ice cube, you can melt it into the water again. Ask yourself: Is the change reversible? Not all physical changes are easy to reverse.Was there a color change (with exceptions), bubble formation, or formation of a precipitate? These are all signs of a chemical change, not a physical change.Is the chemical identity of the end product the same as it was before the change? If the answer is yes, its a physical change. If the answer is no, its a chemical change. Examples of Physical Changes Remember, the appearance of matter changes in a physical change, but its chemical identity remains the same. Crushing a canMelting an ice cubeBoiling waterMixing sand and waterBreaking a glassDissolving sugar and waterShredding paperChopping  woodMixing red and green marblesSublimation of  dry iceCrumpling a paper bagMelting solid sulfur into liquid sulfur. This is an interesting example since the state change does cause a color change, even though the chemical composition is the same before and after the change. Several nonmetals, such as oxygen and radon, change color as they change phase.Chopping an appleMixing salt and sandFilling a candy bowl with different candiesVaporizing liquid nitrogenMixing flour, salt, and sugarMixing water and oil Indications of a Chemical Change Sometimes the easiest way to identify a physical change is to rule out the possibility of a chemical change. There may be several indications that a chemical reaction has occurred. Note: Its possible for a substance to change color or temperature during a physical change. Evolving bubbles or releasing gasAbsorbing or releasing heatChanging colorReleasing an odorInability to reverse the changePrecipitation of a solid from a liquid solutionFormation of a new chemical species. This is the best and surest indicator. A change in the chemical properties of the sample may indicate a chemical change (e.g., flammability, oxidation state).