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 don't 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, it's a physical change. If the answer is no, it's 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 can
• Melting an ice cube
• Boiling water
• Mixing sand and water
• Breaking a glass
• Dissolving sugar and water
• Shredding paper
• Chopping wood
• Mixing red and green marbles
• Sublimation of dry ice
• Crumpling a paper bag
• Melting 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 apple
• Mixing salt and sand
• Filling a candy bowl with different candies
• Vaporizing liquid nitrogen
• Mixing flour, salt, and sugar
• Mixing 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: It's possible for a substance to change color or temperature during a physical change.

• Evolving bubbles or releasing gas
• Absorbing or releasing heat
• Changing color
• Releasing an odor
• Inability to reverse the change
• Precipitation of a solid from a liquid solution
• Formation 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).