Chapter 17:classification of matter

1. Chapter 17:classification of matter Section 1—Composition of Matter

3. MATERIALS ARE MADE OF A PURE SUBSTANCEOR 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

4. 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)

5. 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.

6. 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)

7. HETEROGENEOUS MIXTURE • You might be wearing another heterogeneous mixture…permanent-press fabrics contain fibers of 2 materials (POLYESTER AND COTTON)

8. 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.)

9. 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.

10. 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)

11. COLLOIDS FOREST--FOG HEAD LIGHTS--FOG

12. 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.

14. 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

16. HOMOGENEOUS OR HETEROGENEOUS MIXTURE?

17. CHAPTER 17:CLASSIFICATION OF MATTER Section 2- Properties of Matter

18. 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

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

20. 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.

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

22. 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.

23. 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.

25. 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.

26. 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

27. 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.