Chapter 1: Matter and Change

1. Chapter 1: Matter and Change

2. 1.1 Chemistry • Chemistry is the study of the composition of substances and the changes they undergo. • Can be as simple as the science behind ice melting, to as complicated as impulses carried by your nerve cells. • The “Central Science” • Contributes to biology, geology and physics. Chinese/Japanese character for chemistry literally means “change study”

3. 1.2 The Scientific Method • You’ve covered this before in other classes. • Pg. 4-5 of text. • Theory: A well-tested explanation for a natural event. • Law: A summary of observations about natural events.

5. 1.3 Properties of Matter • What is matter? • Matter is anything that takes up space (has volume) and has mass. • Mass: The amount of matter than an object contains. • Substances • Table sugar is 100% sugar (table sugar is sucrose). • Table sugar is a substance • A substance is a kind of matter that has a uniform and definite composition. • Is lemonade a substance? Air? Water?

6. Physical Properties • All samples of a substance have identical physical properties. • A physical property is a quality or condition of a substance that can be observed or measured without changing the substances composition. • This is really wordy. Give me examples. • Color, mass, odor, hardness, density, melting point, and boiling point are all examples. • We use physical properties to help identify substances.

7. Example • Pg. 8 of textbook, table 1.2 • If I give you a white solid that melts at 800°C, what substance would it probably be? • How about a colorless liquid that couldn’t be frozen in your home’s freezer? • Hint: Melting point and freezing point are the same thing.

8. Homework • Read pg. 3-8 • Do: • Pg. 6, #4 • Pg. 7, #5 • Pg. 8 #6 • Pg. 22-25, #29, 30, 54, 59a, 62, 65

9. 1.4 The States of Matter • The same substance, like water, can exist in multiple forms. • Ice, water, steam • Still all water, just different forms of it. • These forms are called physical states. • Physical states are a physical property of the matter

10. Solids • Three main states of matter • Solids • Shape does not depend upon the shape of the container • Solids are matter that has a definite shape and volume. • Particles packed together tightly. Most are incompressible, and expand only slightly when heated.

11. Liquids • Liquids • Particles in a liquid are in contact with each other, but packed less tightly than in a solid. • Almost incompressible, but expand when heated. • Liquid flows • Takes the shape of the container in which it is placed • However, volume remains the same for a given sample, regardless of the container.

12. Gases • Gasses • Flow to take the shape of the container that holds them • Particles spaced far apart • Expand without limit to fill any space • Easily compressible • Takes both shape and volume of container

13. Gas ≠ Vapor • Term gas is reserved for a substance that exists in the gaseous state at room temperature • The word vapor describes a substance, although in the gaseous state, is generally a solid or liquid at room temperature. • Water is a liquid, though it can be a vapor when heated

14. 1.5 Physical Changes • Matter can be changed in many ways without altering its composition. • Cutting, grinding, bending, melting, freezing, boiling • These transformations that do not alter a substance’s composition are called physical changes.

15. Homework • Read • Pg. 9 – 11 (up until mixtures) • Do • Pg. 10, #7 and 8 • Pg. 11, #9 and 10 • Pg. 22-25, #31, 32, 33, 61, 63

16. 1.6 Mixtures • What is it to create a mixture? • A salad is a mixture. • Soil is a mixture. • Lemonade is a mixture. • Air is a mixture. • A mixture consists of a physical blend of two or more substances. • NOT substances.

17. Granite, salad, air, kool-aid are all mixtures. • Is there a difference in how they look though? In general? • There are different types of mixtures. • Heterogeneous Mixtures • Not uniform in composition. • If you sample one portion of the mixture, will be different from any other portion. • Which of the above would be a heterogeneous mixture?

18. Homogeneous Mixture • Completely uniform composition • Any given sample should be the same • Composition can still vary

19. Phase • Any part of a system with uniform composition and properties • Homogeneous mixtures have one phase • Heterogeneous mixtures have two or more phases • Vinegar and oil dressing has 2 phases, an oil phase and a water phase

20. 1.7 Elements and Compounds • By physically separating mixtures, you can obtain pure substances • Remember, substances have uniform and definite compositions • Two groups of pure substances • Elements • Compounds

21. Elements • Simplest form of matter that can exist under normal laboratory conditions • Cannot be separated into simpler forms by chemical reactions • Examples • Iron, sulfur, carbon, hydrogen, oxygen • Fe, S, C, H2

22. Compounds • Substances that can be separated into simpler substances only by chemical reactions • Made when two or more elements combine chemically • Examples: • Water (H2O), octane (C8H18) • Page 15 summarizes with flow-chart

23. Homework • 12-14, 36, 38, 40, 56

24. 1.8 Chemical Symbols • All matter in the universe is made of elements. • Each element is represented by a chemical symbol. • Generally, chemical symbol consists of the first one or two letters of the name of the element. • Carbon  C • Lithium  Li • Neon  Ne

25. Not always the case though. Some elements are derived from older Latin names. (pg. 17) • Sodium  Na (Natrium) • Copper  Cu (Cuprum) • Gold  Au (Aurum) • Lead  Pb (Plumbum) • First letter of symbol ALWAYS capitalized. • Second letter (if applicable) always lowercase.

26. 1.9 Chemical Reactions • In a chemical reaction, one or more of the substances change into a new substance. • The substance(s) you start with, called the reactant(s). • The substance(s) you end with, called the product(s) •  represents “are changed into” • Example, iron and sulfur chemical react to form iron sulfide.

27. Can be viewed as: Iron + Sulfur  Iron sulfide reactants product • Indications of a chemical reaction • Energy given off or taken in (becomes warmer or colder) • Color change • Production of a gas or solid • Note: Some of these can occur during a physical change as well.

28. Chemical Properties • Just like every substance has physical properties, all have chemical properties. • The ability to undergo chemical reactions and to form new substances. • Only observed when a substance undergoes a change in composition (and therefore a chemical change) • Words like rot, rust, decompose, ferment, corrode, grow, decay, sprout, react usually signify a chemical change.

29. 1.10 Conservation of Mass • Law of Conservation of Mass • In any physical or chemical reaction, mass is neither created nor destroyed; it is conserved • In other words, the mass of the products equals the mass of the reactants

30. Questions • Classify the following changes as physical or chemical • Bread is baked • Salt dissolved in water • Milk spoils • A snowflake melts • Why is the conservation of mass a law and not a theory? • When powered iron is left exposed to the air it rusts. Explain why the rust weighs more than the original powered iron. • Hydrogen and oxygen react chemically to form water. How much water would be formed if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?