SECTION 2: PROPERTIES
OF MATTER
Warm-up:
•Panning for gold was a common
technique used to separate gold
from sand and gravel.
•What properties of gold allow it to be
easily separated from sand and
gravel?
Learning Goals
•Identify substances using
physical properties.
•Compare and contrast physical
and chemical changes.
•Identify chemical changes.
•Define the law of conservation
of mass.
Physical Properties
•Physical Property: any
characteristic of a material that
you can observe without
changing its identity.
•Examples: color, shape, size, density,
melting point, boiling point
Physical Properties
Physical Changes
•Physical Change: a change in
size, shape, or state of matter.
•The identity of the material stays the
same!!!
•Examples:
Physical Change
cutting
boiling
breaking
tearing
Separating mixtures
melting
Physical Change
•Liquid water freezes into ice cubes
•It’s STILL WATER!!!
•Rain in a forest turns the dirt into
mud
•It’s STILL DIRT(just wet)!!!!
•A piece of paper is torn into strips
•It’s still paper!
Physical Change
•When a substance changes
phase (like when water freezes
or boils), it undergoes a physical
change!
Separation
•The best ways to separate
substances depends on their
physical properties.
Separation
•Filtration separates
substances by size.
•Magnets can be
used to separate
magnetic
substances from
non-magnetic
materials.
Separation
•Many areas that lie close to the sea
obtain drinking water by separating
it from the salt.
•The sea water is boiled and the
steam is collected. Salt will not boil
with the water, it has a much
higher boiling point.
Separation
•Distillation: the process of
separating substances in a
mixture by evaporating a liquid
and collecting the steam. The
steam is then cooled down to
form a liquid again.
Chemical Properties
•Chemical Property: a
characteristic of a substance
that can only be measured by
changing the identity of a
substance.
•Examples: flammability, reacts with
acid
Chemical Change
•Chemical change: a change of
one substance into another.
•All chemical reactions are chemical
changes.
Chemical Change
• Four good indicators of a chemical change:
color change
gas released
(often with an odor)
energy change
(light, heat, …)
solid formed
Conservation of Mass
•Burning a log is an example of
a…
•Chemical change!
•The log seems to disappear, and
you are only left with ash.
•What happened to the rest of it?
Conservation of Mass
•The log undergoes chemical
changes and releases carbon
dioxide, water, and smoke.
•It doesn’t just disappear, it all
goes somewhere.
Conservation of Mass
•Law of Conservation of Mass:
the mass of all substances
present before a chemical
change is equal to the mass of
all of the products after a
change.
Check-in:
•Explain why evaporation of
water is a physical change and
not a chemical change.