Transcript Physical/chemical changes ppt

Physical and
Chemical
Properties and
Changes
Physical Properties
Are a substance’s characteristics that can
be observed.
Qualitative Examples:
How something can look, smell,
or sound
States of matter (solid, liquid, or gas)
Physical Properties
Quantitative
•
•
•
•
•
More Examples:
Volume
Area
Length
Mass
Temperature
More Physical Properties
Viscosity- the tendency of a liquid to resist
flow.
Conductivity- the ability to allow heat to
flow.
Malleability- the ability of a solid to be
hammered without shattering
Hardness- the ability to scratch another
substance
Melting Point- the temperature at which a
solid changes into a liquid
Boiling Point- the temperature at which a
liquid changes into a gas
Density- defined as mass / volume
Physical Changes
Include:
1) Change of property
2) Creation or separation of a mixture
3) Physical deformation (cutting,
bending, crushing, etc…)
melting
evaporating
Energy absorbed by particles------------
------------Energy released by particles
freezing
condensing
Physical Properties
This includes:
• Boiling point
• Melting point
• Freezing point
Chemical Properties- any
ability to produce a change in the
composition of matter.
1)
2)
3)
4)
Flammability
pH
Reactivity
Corrosiveness
Chemical Properties
Flammability – is a material’s ability to burn
in the presence of oxygen
Reactivity- the property that describes how
readily a substance combines chemically
with other substances
Corrosiveness- causing damage
to metal or other materials
through a chemical process
pH - a measure of acidity and alkalinity of a
solution that is a number on a scale (1 -14)
on which a value of 7 represents neutrality
Chemical Changes
• Occur when a substance goes through a
chemical reaction. Rearranges atoms into
new substances. The reaction cannot be
reversed by ordinary processes.
Examples:
Leaves changing
color in the fall.
Baking a cake.
The batter absorbs
energy and changes
into a new substance
with different
properties.
Evidence of a chemical change:
1)
2)
3)
4)
Produces gas or bubbles
Color changes
Not easily reversed
Light, heat, or sound is released
• The only PROOF is a new substance
formed with different properties
Example:
nail
silver
magnetic
rusted nail
orangish/brown
not magnetic
Review
Classify the following scenarios as either
physical or chemical changes.
Scenario
Baking a Cake
Melting Snow
Pouring water
into a graduated
cylinder
Burning a candle
Physical Change
Chemical Change
Mixing the
batter
Odor change,
color change,
not easily reversed
Change in state
of matter
Change in
shape
Melting the
wax
Odor, new gas,
heat or light
Mushrooms act as decomposers in
the rainforest
Is decomposition a physical change or chemical change? Explain
Leaf cutter
ants carry
leaves back to
their nest and
grind the
leaves into
pulp. A
fungus grows
on the pulp
and is used as
food for ants.
Explain both the physical and
chemical changes of their actions.