Transcript Chapter 17:classification of matter

CHAPTER 17:CLASSIFICATION
OF MATTER
Section 1—Composition of Matter
MATERIALS ARE MADE OF A PURE SUBSTANCE OR
A MIXTURE OF SUBSTANCES.
 A PURE SUBSTANCE, or simply a substance, is
either an element ( iron or silver) or a
compound (NaCl, H2O).
 Substances cannot be broken down into
simpler compounds and still maintain the
properties of the original substances.
(Ex.’s –helium, aluminum, water, salt)
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C
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ELEMENTS
 All substances are built
from atoms.
 If all the atoms in a
substance are alike, that
substance is an element.
 (Ex.’s--graphite in
pencil—all carbon
atoms; copper coating in
pennies—all copper
atoms; gold bar—all
gold)
COMPOUNDS
 2 or more elements can
combine to form
substances called
compounds.
 A compound is a
substance in which the
atoms of 2 or more
elements are combined.
(Ex. Water=H2O—2
atoms of hydrogen, 1
atom of oxygen.
MIXTURES—A mixture that can be distinguished easily is called
a heterogeneous mixture.
 Heterogeneous
mixtures—are
mixtures made of 2
or more substances
that can be easily
separated by physical
means. (Ex. Bowl of
mixed nuts)
HETEROGENEOUS MIXTURE
 You might be
wearing another
heterogeneous
mixture…permanent
-press fabrics contain
fibers of 2 materials
(POLYESTER AND
COTTON)
MOST OF THE SUBSTANCES YOU COME INTO CONTACT
WITH EVERY DAY ARE HETEROGENEOUS MIXTURES.
 Some are easy to see,
like the ingredients
in a PIZZA, but
others are not.
 In fact, the
component you see
can be a mixture
itself.
 (Ex. CHEESE--contains milk,
proteins, butter fat, colorings,
and other food additives.)
HOMOGENEOUS MIXTURES
 A homogeneous mixture contains 2 or more
gaseous, liquid, or solid substances blended
evenly throughout.
 Ex. Soft drink: water, sugar, flavoring, coloring,
and carbon dioxide gas—can/flat—NOT OPEN
 Another name for a homogenous mixture is called
a solution.
 A solution’s particles are so small that they cannot
be seen with a microscope and will NEVER settle
to the bottom of their container.
COLLOID
 A colloid is a type of mixture that never
settles.
 Its particles are larger than those in solutions,
but NOT heavy enough to settle.
(Ex. Milk, fog, smoke)
COLLOIDS
FOREST--FOG
HEAD LIGHTS--FOG
DETECTING COLLOIDS—You can tell for certain if a
liquid is a colloid by passing a beam of light through it.
 A light beam is INVISIBLE as it passes through
a solution, BUT can be SEEN as it passes
through a colloid.
 The particles in a colloid are LARGE enough
to SCATTER light, but those in a solution are
NOT.
 The SCATTERING OF LIGHT by colloidal
particles is called the Tyndall effect.
SUSPENSIONS
 Some mixtures of neither solutions nor
colloids. (Ex. MUDDY pond water, apple
CIDER (NOT juice)
 POND WATER is a suspension, which is a
heterogeneous mixture containing a liquid in
which visible particles SETTLE.
 Other examples--orange juice with pulp,
liquid medicines
HOMOGENEOUS OR HETEROGENEOUS
MIXTURE?
CHAPTER 17:CLASSIFICATION OF MATTER
Section 2- Properties of Matter
PHYSICAL PROPERTIES
 Any characteristics of a
material that you can
observe without
changing the identity
of the substances that
make up the material
is a physical property.
 Examples--APPEARANCE:
color, shape, size, melting
point, boiling point;
BEHAVIOR: attraction to a
magnet, ability to flow
PHYSICAL PROPERTIES—The best way to separate
substances depends on their physical properties.
SIZE—ROCKS/SAND
MAGNETISM—
IRON/SAND
PHYSICAL CHANGE
 A change in SIZE, SHAPE, OR STATE OF
MATTER is called a physical change.
 These changes might involve energy changes,
but the kind of substance—the
IDENTITY of the element or compound—
DOES NOT CHANGE.
DISTILLATION
 Distillation is a
process for
separating
substances in a
mixture by
EVAPORATING
liquid and
RECONDENSING its
vapor.
 Ex. Purifying water
(distilled water)
CHEMICAL PROPERTIES
 A chemical property is a characteristic of a
substance that indicates whether it can change
into another substance.
 Ex. Flammability, or the tendency of a
substance to burn, because burning produces
NEW SUBSTANCES.
DETECTING CHEMICAL CHANGE
A change of one substance to another is a
chemical change.
 Ex.’s—RUST on car fenders, SMELL of rotten
eggs, food BURNING in the oven, FOAMING
of an antacid tablet in water
 In some chemical changes, a RAPID
RELEASE OF ENERGY---detected as HEAT,
LIGHT, AND SOUND—are CLUES that
changes are occurring.

WEATHERING—CHEMICAL OR
PHYSICAL CHANGE?
 PHYSICAL CHANGE—
 Large rocks can split
when water seeps into
small cracks , freezes,
and expands.
 However, the smaller
pieces of newly
exposed rock still have
the SAME
PROPERTIES as the
original rock.
CHEMICAL CHANGE
 Solid calcium carbonate, a
compound found in
limestone, does not
dissolve easily in water.
However, when the water is
slightly acidic, a new
compound is formed.
 Slightly acidic water (CO2
and H2O) and calcium
carbonate calcium
hydrogen carbonate (NEW
SUBSTANCE)
 Ex.’s—Caves
CONSERVATION OF MASS—Matter is neither
created nor destroyed during a chemical change.
Burning log + oxygen = ashes +
smoke + gases that escaped
from log
LAW OF CONSERVATION OF MASS
 The MASS of all
substances BEFORE a
chemical change
EQUALS the MASS of
all the substances
that remain AFTER
the change.