1. Physical and Chemical Changes
8th Grade Physical Science
Betsy Sanford

2. Physical Property Observed traits, qualities, attributes
Help describe/identify a substance
Can be seen or measured without changing a substance
Examples:
color, shape, smell, taste
Measurements - mass, volume, density
state (solid, liquid, gas)
temperature for change of state – melting point, freezing point, boiling point

3. Physical Property More examples:
ductility (ability to be made into wires)
malleability (ability to be shaped without breaking)
conductivity (ability to carry electric current or heat)
solubility (ability to dissolve)

4. Physical Change
Any change in size, shape, form, or state where the identity of the matter stays the same
Example:
cutting a watermelon into slices
tearing a sheet of paper
sharpening a pencil
Often easy to reverse with:
filtration, magnetism, evaporation, distillation and centrifuge (spinning)

5. Physical Change More examples: boiling freezing melting condensing
evaporating
stretching into wire
hammer into sheet
Dissolving sugar in tea
transferring heat or electricity

6. Physical Change Evidence for a physical change:
same substance before and after
no new substances
a color change
a state change (solid, liquid, gas)
same smell, taste, texture
different volume
different density

7. Chemical Property Traits that allow a substance to change
Testing for chemical properties causes a change in the substance
Examples:
flammability (ability to catch fire)
combustibility (ability to explode)
reactivity with oxygen
reactivity with water
acidity (pH, reaction with hydrogen)

8. Chemical Change
chemical change happens when a substance undergoes a change that causes its traits to change
new materials are formed that are different from the starting materials
Examples:
digestion (breakdown of food)
photosynthesis (plants making food)
burning fuel
exploding fireworks
rusting
formation of different gas

9. Chemical Change NOT easily reversed Evidence for a chemical change
more than one of the following occurs:
release of energy (light, heat, sound – change in temperature)
formation of new substance (a different gas or solid that is not just a state change)
color change, odor change
change in conductivity

10. Chemical Change Chlorine added to swimming pools and drinking water
causes acidity (change in pH)
prevents reproduction, growth and development of algae, bacteria, protists and insects.

11. Energy…
…is required for both types of changes

12. Table of Physical and Chemical Changes
Physical Changes
Chemical Changes
Paper cut in half
Sour milk
Modeling clay
Tarnished jewelry
Butter melting
Burned toast
Ice forming
Rust on a nail
Water evaporating
Gas grilling
Sweet tea
Apple rotting
Bowl of cereal
Frying an egg
Makeup on your face
Lit match
Crushing a can
Cellular respiration

13. Lab Evidence - Physical vs. Chemical Change
Physical Changes
Chemical Changes
color change
substance is the same, but may be a different size or shape
new substance
changing state
fizzing or foaming
dissolving
heat gain or heat loss
bending, crushing
production of sound, light, or odor
mixing, cutting
change cannot be undone