
Unit 2.3 – Physical and Chemical
Properties
and
Unit 2.4 – Physical and Chemical Changes

Physical Property – a characteristic of a pure
substance (element, compound, molecule)
that can be observed without changing it into
another substance.

Examples of Physical Properties:
◦ Taste – what does it taste like?
◦ Color – what color(s) make up the matter?
◦ Texture – how does it feel?
◦ Density
◦ Physical State (solid, liquid, gas)
◦ Shape
◦ Flexibility – if you bend it, will it break or change shape

Give me as many physical properties of this
piece of chocolate cake as you can!
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◦
◦
◦
◦
◦
◦
◦
Taste ______________________
Color ________________________
Texture _____________________
Density ____________________
Physical State (solid, liquid, gas)
Shape _____________________
Flexibility __________________
Smell _ __ _ _ _ ___ _ ________
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
Chemical Property – a characteristic of a pure
substance (element, compound, molecule)
that describes its ability to change into
different substances
In order to find the chemical properties of a
substance, you will have to test the pure
substance and possibly change it (unlike with
physical properties).

Examples of Chemical Properties:
◦ Flammability – can it burn if a fire source is applied
to the matter being described
 Example: If you apply a fire source to charcoal, it will burn
◦ Ability to react with other matter – if combined or
mixed, with the matter react with another form of
matter
 Example: We are looking at the chemical properties of
vinegar (acetic acid). If you combine vinegar with water, then
you just get a mixture. But it you combine vinegar with
baking soda (sodium bicarbonate), it reacts!

Give me as many chemical properties of
this piece of iron (car)
◦ Ability to react with other matter – if
combined or mixed, will the matter react with
another form of matter
______________________________
◦ Flammability – can it burn if a fire source is
applied to the matter being described
◦ ____________________________________
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Matter can change
Examples: Freeze, cut, burn, etc.
2 types of changes of matter
1. Physical changes
2. Chemical changes


Physical Change – any change that alters the form
or appearance of matter but does not make any
substance in the matter into a different substance
Any substance that undergoes a physical change is
still the same chemical substance

The most common example is a change of state of
matter
Example: melting ice can be refrozen.

Physical changes can be reversed!
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
Example of physical changes are changes of
states of matter.
◦ Boiling of water – the physical change is from a
liquid state of water to a gaseous state of water.
 This change of state is called evaporation, boiling or
vaporization.
 Liquid water (H2O) when it undergoes boiling is
changed into gaseous water (water vapor) H2O.
Regardless, it is still chemically H2O

Physical changes are cause by changes in
thermal energy.


Matter changes form WITHOUT becoming
something new
It is a change in size or shape usually
◦ You start and end with same thing (see below)

Examples: cutting, freezing, melting, etc.

INCREASE OF THERMAL ENERGY (FROM A
SOLID TO A GAS)

Melting – when a solid is turning into a liquid.

Boiling, vaporization, or evaporation– when a
liquid is turning into a gas.

DECREASE OF THERMAL ENERGY (FROM A
SOLID TO A GAS)

Condensing – when a gas is turning into a
liquid.

Freezing – when a liquid is turning into a
solid.
solid
melting
evaporation
Increase in
thermal energy
Increase in
thermal energy
Some
molecule
movement
gas
liquid
Lots of
molecule
movement
Little
molecule
movement
Decrease in
thermal energy
freezing
Decrease in
thermal energy
condensation
Boiling Point
Melting Point
Melts
Solid
Liquid
Freezes
Freezing Point
Boils
Gas
Condenses
Condensation Point
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
Sublimation – when a solid turns directly
into a gas and skips the liquid state–
ex. Dry Ice
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
Chemical Change (a.k.a. Chemical Reaction) – a
change in matter that produces one or more new
substances
Any substance that undergoes a chemical change
is NOT the same chemical substance
Some common examples of chemical changes are
burning, rusting, and tarnishing.
Chemical changes cannot be reversed!
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
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Combustion (burning) –
when a fuel source
combines with oxygen to
produce a new substance.
Usually heat and light are
produced
Oxidation (rusting) – slow
combination of a substance
with oxygen
Tarnishing – combination of
a bright metal with sulfur
that produces a dark
coating

A burning piece of wood is hard to change
back into a whole piece of wood.

Matter changes, becomes NEW substance
◦ Start and end with different things


Usually irreversible (can’t change back)
Examples: burning, rusting, milk going sour

Reactants: starting
solutions in a reaction

Products: the
resulting solutions in
a reaction
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

The atoms arrange to make a new
substance
The matter is not the same molecules after
a chemical change or reaction
2H2 + O2  2H2O

Chemical changes usually have tell-tell signs that
indicate that a reaction has occurred.
◦
◦
◦
◦
◦
Temperature
Color change
Bubbles/fizzing
Production of smoke
Smell
NaHCO3 + HOOCCH3
Baking Soda + Vinegar
NaOOCCH3 + H2O+ CO2
Sodium Acetate + water + carbon dioxide
 Sugar
in tea
dissolving
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?
 Logs
burning
•Chemical Change
•Physical Change
Did it change size orshape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?

Breaking water up by
separating it into hydrogen
and oxygen
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?
 Cutting
paper
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?
 Crushing
aspirin
an
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?
 Metal
rusting
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?
 An
egg rotting
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?
 An
egg breaking
•Chemical Change
•Physical Change
Did it change size or shape (Physical
Change)?
or
Did it become different matter
(Chemical Change)?