Classifying Changes of Matter:
Physical vs. Chemical
Physical Change
Physical
A change in matter from one form to
another without changing its chemical
properties
(most can be reversed)
No change in atoms/molecules
Physical Change
• Examples =
 Change in state or phase change
 Dissolving
 Compressing
 Light emission/absorption
 Electrons passing through metals
Physical Change
More Examples =
• boiling of a liquid
• melting of a solid
• dissolving a solid in a liquid
to give a homogeneous
mixture
• making a solution
2
1
Chemical Change
Chemical
Bonds are made / broken
Change in oxidation states
Cl-1
Cl-1
Li
+1
Examples of Chemical Change
•Burning hydrogen (H2) in oxygen
(O2) gives H2O.
• Chemical change or chemical
reaction — transformation of
one or more atoms or
molecules into one or more
different molecules.
Sure Signs of a Chemical Change
• Heat
• Light
• Gas Produced
(not from boiling!)
• Precipitate – a
solid formed by
mixing two liquids
together
Physical vs. Chemical Change
• Examples:
▫ melting
physical
▫ flame produced
chemical
▫ paper cut
▫ dissolving salt in
water
▫ tarnishes in air
physical
physical
chemical
Physical vs. Chemical Change
• Examples:
▫ rusting iron
chemical
▫ mixing mud and water physical
▫ burning a log
▫ freezing water
▫ grinding spices
chemical
physical
physical
• A difference between physical change
and chemical change is that
1. chemical change involves energy while physical
change does not.
2. physical change involves energy while chemical
change does not.
3. different kinds of molecules are present after a
physical change but not after a chemical change.
4. different kinds of molecules are present after a
chemical change but not after a physical change
In making a pizza, which
process involves a chemical
change?
1. Mixing spices for the
sauce
2. Slicing pepperoni for
the topping
3. Spreading cheese on the
pizza
4. Baking the dough to
form the crust