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)
E E C C

 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)

 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)

 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.)

 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.

 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)

FOREST--FOG HEAD LIGHTS--FOG

—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.

 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


 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

—The best way to separate substances depends on their physical properties.
SIZE—ROCKS/SAND
MAGNETISM—
IRON/SAND

 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 is a process for separating substances in a mixture by
EVAPORATING liquid and
RECONDENSING its vapor.
 Ex. Purifying water
(distilled water)

 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.




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.

 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.




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

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.