Do Now: physical and chemical change
• Describe 2 changes that will occur for
this plastic garbage bag as it is filled with
heavy objects
• Describe 2 changes that will occur for
the bag as it comes in contact with fire
Lesson 4 Learning Target
1. Identify conditions under which properties of a
material are changed, and critically evaluate if a new
substance has been produced
2. Observe and infer evidence that a chemical reaction
has occurred between familiar household materials
Physical and chemical change
The change that matter undergoes can be classified in one of two ways:
Physical: the material changes its form but not its
chemical composition; often reversible
• Example: the garbage bag ripped when too
much weight was added to it, but the
plastic is still the same
• Example: when ice melts, its state of matter
has changed but its chemical formula (H₂O)
is the same
Chemical: the material changes in such a way that at
least one new substance is formed; usually irreversible
• Example: the garbage bag burning
(combusting) produced carbon dioxide
and the plastic became thicker, harder, and
less flexible
• Example: cooking an egg is irreversible and
changes the chemical formula of the egg.
Physical properties
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Color
Texture
Taste
Smell
State (solid, liquid, gas)
Malleability (ability to be
hammered into a sheet)
• Ductility (stretchiness)
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Melting temperature
Boiling temperature
Density
Viscosity
Solubility (ability to dissolve)
Electrical conductivity
Heat conductivity
Chemical properties
Chemical properties
Reacts with water
Reacts with air
Reacts with pure oxygen
Reacts with acids
Reacts with other pure substances
toxicity
combustibility
Chemical changes during a reaction
A chemical change has likely taken place if you make at
least 2 of the following observations during a reaction:
• Heat is produced or absorbed
• The starting material is used up
• There is a color change
• Gas bubbles form in a liquid
• A precipitate (solid) forms in a liquid
• The change is difficult to reverse
Check your understanding
Write “P” for a physical change and “C” for a chemical change
1. Water freezing to form snow Physical
2. A cake baking Chemical
3. Lighting a match Chemical
4. Gasoline evaporating at the gas station Physical
5. Steam condensing on the bathroom mirror Physical
6. Melting gold to cast gold bars Physical
7. Dynamite exploding Chemical
8. Bleaching a stain Chemical
9. Dissolving eggshell in acetic acid Chemical
10. Popping popcorn Physical
Physical and chemical change - Lab
Question: are the changes at each step
of the experiment physical or
chemical?
Textbook pg. 102