Examples of Physical Changes and Chemical Changes

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. Key Takeaways: Chemical and Physical Change Examples A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity.Examples of chemical changes are burning, cooking, rusting, and rotting.Examples of physical changes are boiling, melting, freezing, and shredding.Often, physical changes can be undone, if energy is input. The only way to reverse a chemical change is via another chemical reaction. Examples of Chemical Changes A new compound (product) results from a chemical change as the atoms rearrange themselves to form new chemical bonds. Burning woodSouring milkMixing acid and baseDigesting foodCooking an eggHeating sugar to form caramelBaking a cakeRusting 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 foilMelting an ice cubeCasting silver in a moldBreaking a bottleBoiling waterEvaporating alcoholShredding paperSublimation of dry ice into carbon dioxide vapor How to Tell Whether Its 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 dont see any of these indications, a physical change likely occurred. Be aware a physical change may produce a dramatic change in the appearance of a substance. This doesnt mean a chemical reaction 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. Learn More 10 Examples of Physical Changes10 Examples of Chemical ChangesChemical and Physical PropertiesUnderstanding Chemical and Physical Changes Source Zumdahl, Steven S. and Zumdahl, Susan A. (2000). Chemistry (5th Ed.). Houghton Mifflin. ISBN 0-395-98583-8.