Ch. 2 “Matter”
Section 2.3
“Properties of Matter”
“Chemical and Physical Properties”
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
Chemical property = the way a substance
reacts with others to form new substances with
different properties
Examples:
sodium, magnesium, tungsten = very reactive
gold = not very reactive
argon = not reactive
Chemical properties involve the reactivity of
elements or compounds.
“Chemical and Physical Properties”
Physical property = a characteristic of a
substance that can be observed or measured
without changing the composition of the substance
Examples:
1. shape
7. strength
2. color
8. hardness
3. odor
9. ability to conduct electricity
4. texture
10. ability to conduct magnetism
5. melting point
11. ability to conduct heat
6. boiling point
Density
1.
2.
Density = the mass per unit volume of a
substance
low density = “light”
high density = “heavy”
Take a look at the two boxes below. Each box has
the same volume. If each ball has the same mass,
which box would weigh more? Why?
Density
Density Equation:
D=m/V
density = mass / volume
Variations:
V=m/D
m=D•V
 The density of a liquid or solid is usually reported in units
of grams per cubic centimeter. Liquids can also be
expressed as grams per milliliter.
Density
1. Why do helium balloons float?
2. Why do hot air balloons float?
3. How is skim milk made?
4. Why does ice float?
The force with which a more dense fluid
pushes a less dense substance upward
is known as buoyancy.
Properties Help Determine Uses
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3.
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We use physical properties to help us select
substances that may be useful to us.
Why is copper used in electrical lines?
Why is antifreeze and not water used in a car’s
radiator?
Why is surgical steel used to reinforce broken
bones?
Why are concrete and glass used as building
materials?
Why is liquid gasoline used in a car engine?
Chemical and Physical Changes
Chemical change = a change that occurs when a
substance changes composition by forming one or more
new substances
Ex: photosynthesis = 6CO2 + 6H20  C6H12O6 + 6O2
Evidence of a chemical change:
1. change in color
2. the release of a gas
3. the formation of a precipitate (a solid that will settle out
of a liquid or gas)
4. the absorption or release of heat.
Ex. Of chemical changes:
1. rust
2. fermentation
3. explosion
4. flames
Chemical and Physical Changes
Physical change = a change in the
physical form or properties of a substance
that occurs without a change in
composition.
Ex:
1. grinding peanuts into peanut butter
2. pounding a gold nugget into a gold ring
3. solid water melting into liquid water
4. dissolving sugar into water