Examples of Physical Changes and Chemical Changes

What Are Some Physical and Chemical Changes?

Burning logs
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Are you confused about the difference between chemical changes and physical changes and how to tell them apart? In a nutshell, a chemical change produces a new substance, while a physical change does not. A material may change shapes or forms while undergoing a physical change, but no chemical reactions occur and no new compounds are produced.

Examples of Chemical Changes

A new compound (product) results from a chemical change as the atoms rearrange themselves to form new chemical bonds.

  • burning wood
  • souring milk
  • mixing acid and base
  • digesting food
  • cooking an egg
  • heating sugar to form caramel
  • baking a cake
  • rusting of iron

Examples of Physical Changes

No new chemical species forms in a physical change. Changing the state of a pure substance between solid, liquid, and gas phases of matter are all physical changes since the identity of the matter does not change.

  • crumpling a sheet of aluminum foil
  • melting an ice cube
  • casting silver in a mold
  • breaking a bottle
  • boiling water
  • evaporating alcohol
  • shredding paper
  • sublimation of dry ice into carbon dioxide vapor

How to Tell Whether It's a Physical or Chemical Change?

Look for an indication that a chemical change occurred. Chemical reactions release or absorb heat or other energy or may produce a gas, odor, color or sound. If you don't see any of these indications, a physical change likely occurred.

In some cases, it may be hard to tell whether a chemical or physical change occurred.

For example, when you dissolve sugar in water, a physical change occurs. The form of the sugar changes, but it remains the same chemically (sucrose molecules). However, when you dissolve the salt in water the salt dissociates into its ions (from NaCl into Na+ and Cl-) so a chemical change occurs. In both cases, a white solid dissolves into a clear liquid and in both cases, you can recover the starting material by removing the water, yet the processes are not the same.

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Helmenstine, Anne Marie, Ph.D. "Examples of Physical Changes and Chemical Changes." ThoughtCo, Mar. 30, 2017, thoughtco.com/physical-and-chemical-changes-examples-608338. Helmenstine, Anne Marie, Ph.D. (2017, March 30). Examples of Physical Changes and Chemical Changes. Retrieved from https://www.thoughtco.com/physical-and-chemical-changes-examples-608338 Helmenstine, Anne Marie, Ph.D. "Examples of Physical Changes and Chemical Changes." ThoughtCo. https://www.thoughtco.com/physical-and-chemical-changes-examples-608338 (accessed October 21, 2017).