Matter - Properties
and Changes
Chapter 3
Substances
• Substance = Matter that has a uniform
and unchanging composition
• Examples are salt and water
• Is seawater a substance?
• Physical property: characteristic
Properties of Matter
that can be observed or
measured without changing the
sample’s composition
• Substances have
unchanging physical
properties
• Density, color, odor, taste,
hardness, melting point,
boiling point, etc...
• Can be extensive (dependent
on the amount; mass, volume,
Chemical Properties
• Chemical Property: The ability of a
substance to combine with or change
into one or more other substances
Conditions that
Observations are
Made
• Properties can be dependent on the
immediate conditions
• Always record the conditions
• Pressure, temperature
• Think of water!
States of Matter
• Solid: Form of matter that has its own
definite shape and volume
• Particles tightly packed, shape is
definite, incompressible
States of Matter
• Liquid: Form of matter that flows, has
constant volume, and takes the shape
of its container
• Particles not rigid, particles can
move past each other, virtually
incompressible
States
of that
Matter
• Gas:
Form of matter
flows to
conform to the shape of its container
and fills the entire volume of its
container
• Particles are far apart, easily
compressible
• Vapor = gaseous state of a substance
that is normally solid or liquid at room
temperature
• Oxygen vs. water vapor?
•
Changes in Matter
(3.2)
Physical changes: altering of a
substance without changing its
composition
•
•
Ice - water - water vapor
Phase changes are physical
changes
•
•
boil, freeze, condense,
vaporize, melt
Temperatures at which
substances do these are
physical properties (intensive)
Teacherweb.com
Chemical Changes
•
Chemical Changes: The process that
involves one or more substances
changing into new substances
•
•
•
•
•
Chemical Reaction
New substances have different
compositions and different
properties
Explode, rust, oxidize, corrode,
tarnish, ferment, burn, rot
Starting substances = reactants
Newly formed substances = products
Silvertarnishing.com
Conservation of Mass
• Law of Conservation of Mass: Mass is
neither created nor destroyed during a
chemical reaction - it is conserved
• Mass
= Mass
• Practice Problems p. 65 6, 7
Reactants
Products
Mixtures of Matter
(3.3)
• On the basis of composition alone, all
matter can be classified into substances
or mixtures
• Mixture = a combination of two or more
pure substances in which each pure
substance retains its individual chemical
properties.
• Composition of mixtures is variable
• Demo
Types of Mixtures
• Heterogeneous: one that does not blend
smoothly throughout and in which the
individual substances remain distinct
• Sand and water, orange juice with
pulp
• Homogeneous: one that has a constant
composition throughout, it always has a
single phase
• Salt and water, powder drink in
water
Separating Mixtures
• Substances in mixtures are physically
combined so they can be physically
separated
• penny and nickel mixture
• salt and water
• sand and water
Filtration
• Heterogeneous mixtures of solids and
liquids are easily separated by filtration
• Uses a porous barrier to let the liquid
through and traps the solids
Distillation
• Based on
differences in
boiling points of
the substances in
a mixture
• Lowest boiling
point turns to a
vapor first and can
then be cooled and
captured
Homechemistry.org
Crystallization
• Separation technique that results in the
formation of pure solid particles of a
substance from a solution containing
the dissolved substance
• Produces highly pure solids
• Rock Candy!
crystal-clear-science-projects.com
Chromatography
• Separates components
of a mixture on the
basis of the tendency
of each to travel or be
drawn across the
surface of another
material
• Separate the colors of
ink in a pen
mason.gmu.edu
Heterogeneous
• Suspensions:
mixture containing
Mixtures
particles that will settle out in left
undisturbed
• Separate through a filter
• Suspended particles are large
compared to other mixtures
• Colloids: mixture containing particles of
intermediate size
• Cannot separate via filtration
• Particles big enough to scatter light