Physical and Chemical
Changes
6.Sc.P.K.11 Contrast physical and
chemical change.
From Properties to Changes
Physical and chemical properties are
characteristics of matter.
Physical and chemical changes are events
that make the matter different somehow.
Physical Change
A change that occurs when one or more
physical properties are changed.
Many physical changes can be undone by
physical means.
Physical Change
Fold a piece of paper
(event).
Does the paper still
have its original
physical properties or
has a new substance
been produced?
It is still made of the same original substance.
No new substance has been produced.
Physical Change
To make nacho cheese
dip, you have to melt
the cheese (event).
Does the cheese still
have its original
physical properties or
has a new substance
been produced?
Even though the cheese turned from a solid to a thick
liquid, it is still made of the same original substance.
No new substance has been created.
Chemical Change
A change that produces new substances.
Most chemical changes cannot easily be
undone.
Chemical Change
Holding a match to a
piece of paper will
cause the paper to
burn (event).
Does the paper still
have its original
physical properties or
has a new substance
been produced?
Ash, gas, and smoke are new substances that have been
produced (all of which have a different composition than
the original paper).
Chemical Change
A metal mailbox is
made of iron is
exposed to oxygen
(water contains
oxygen).
Does the mailbox still
have its original
physical properties or
has a new substance
been produced?
Rust, a new substance, has been produced (ferric oxide
Fe2O3).
Chemical Change
Food you eat goes
through digestion
(event).
Does the food still have
its original physical
properties or has a
new substance been
produced?
Food is broken down in the digestive system and nutrients,
substances that have a different composition than the
original food you ate, are sent to different parts of your
body to provide energy.
Change is Change!
Predict what type of change is occurring with the following:
Prediction Physical Chemical
burning fuel
burning wood
cutting paper
developing film
melting candle wax
melting ice
sharpening a pencil
mixing vinegar and
baking soda
burning fuelGas is ‘burned’ in a car’s
engine through a process
called internal
combustion. When gas is
placed in an enclosed
space and ignited, an
incredible amount of
energy is released in the
form of expanding gas,
which is composed of a
different substance than
the original gas.
Chemical Reaction
Photo courtesy DaimlerChrysler
Jeep® Grand Cherokee Engine
burning woodWhen wood is burned,
you are left with ash,
gas, and smoke, all of
which are new
substances
composed of different
material than the
original wood.
chemical change
cutting paper
After cutting paper, you
are left with smaller
pieces of paper. Are
those pieces of paper
composed of the
same material as the
original paper? YES!
No new substances
are produced.
physical change
developing film
A developing chemical
agent is combined
with the film that a
camera used to store
images on. The
images are exposed
in a format that allows
them to be seen
though new particles.
A new substance is
created.
chemical change
burning candle
Heat is used to melt candle
wax and the heat must be
maintained in order for
the wax to stay melted.
Is the wax still composed
of the same substance
when it is in liquid form?
Yes, even though the wax is
melted, it is still the same
substance.
The wick burns, creating a
new substance; this is a
chemical change.
both physical
change and
chemical change
melting ice
If ice is not kept at a
constant freezing
temperature, it will melt
(event).
Is the melted ice still
composed of the same
substance when it is in
liquid form?
Yes, even though the ice is
melted, it is still the same
substance.
physical change
sharpening a pencil
A wood and graphite pencil
is sharpened by a pencil
sharpener. Are the pencil
shavings still composed
of the same substance or
is a new substance
produced?
Yes, pencil shavings are
just little pieces of the
original pencil.
physical change
vinegar and baking
soda
When baking soda and
vinegar are combined
(event) a bubbly, fizzy
substance appears. Is
this still the same
substance or has a has a
new substance
produced?
Yes, when the two
chemicals combine C02, a
gas, is produced.
chemical change