Ch. 1 Introduction: Some Basic Concepts

1. Ch. 1 Introduction: Some Basic Concepts

2. The study of the composition of matter and the changes that matter undergoes Chemistry

3. Matter • Anything that has mass and takes up space

4. States of Matter

5. Solid • Definite shape AND volume • Incompressible • Particles are packed tightly together

6. Liquid • Definite volume • Takes the shape of its container • Almost incompressible-particles not rigidly packed

7. Gas • Takes the volume and the shape of its container • Particles in a gas are spaced far apart • Easily compressed

8. Vapor • The gaseous state of a substance that is generally a solid or a liquid at room temperature

9. Physical Properties • A quality or condition that can be observed or measured without changing the substances composition • Color, solubility, odor, hardness, density, melting point, boiling point

10. Physical Change • Changes the material without changing the composition • Boiling, freezing, dissolving, melting, condensing, breaking, splitting, cracking, cutting, crushing, bending……… • Usually reversible

11. Pure Substance • Contain only one kind of matter • Have identical physical properties

12. Elements • The simplest forms of matter that can exist under laboratory condition • Can not be separated into simpler substances by chemical means • The building blocks for all other substances

13. Chemical Symbol • One or 2 letters • The first letter is always capitalized

14. Compounds • 2 or more elements chemically combined • Can be separated into simpler substances by chemical means + = Sodium Metal Sodium Chloride Chlorine Gas

15. Compounds • The subscript numbers in chemical formulas represent the proportions of elements that make up the compounds • Pb2(SO4)3 • Pb (lead)  2 • S(Sulfur) 3 • Oxygen  12

16. Law of Definite Proportions (Law of Constant Composition) • The elemental composition of a pure compound is ALWAYS the same • i.e. Water= H2O = 2 Hydrogens: 1 Oxygen ALWAYS

17. 2 Types of Mixtures • Heterogeneous Mixtures • Homogeneous Mixtures

18. Mixture • A physical blend of 2 substances • Compositions may vary

19. Heterogeneous Mixture • One that is NOT uniform in composition

20. Homogeneous Mixture • The same throughout

21. Solution • A homogeneous mixture • Solutions may be solids, liquids, or gases • Same composition throughout

22. Phase • Any part of a system with uniform composition and properties Phase 1 Phase 2

23. Separation of Mixtures Distillation

24. Separation of Mixtures Centrifuge

25. Separation of Mixtures

27. Chemical Property • The ability of a substance to undergo a chemical reaction to form a new substance • I.e. flammability, alkalinity, acidity, rusting • Chemical properties are only observed when a substance undergoes a chemical change

28. Chemical Changes (Reaction) • One or more substances change into new substances • 2 H2 (g) + O2 (g)  2 H2O (g) Reactants Products

29. Chemical Reactions (rust-oxidation)

30. Chemical Reactions (combustion)

31. Chemical Reactions (acid/base)

32. Indicators of a Chemical Reaction • Energy is absorbed or given off (change in temperature) • Change in color • Change in odor • Formation of a solid (precipitation) • Formation of a gas

33. Scientific Method • One logical, systematic approach to the solution of scientific problems. Steps include: • Making observations • Testing hypothesis • Developing theories

35. Observation • Use your senses to obtain information directly

36. Hypothesis • A proposed explanation for an observation based on previous knowledge (or research) • Must be specific • Must be testable • Is only useful if it accounts for what is actually observed

37. A means to test a hypothesis Experiment

38. Manipulated Variable (Independent Variable) • The variable that you can change • Time • Temperature • Volume • Speed • Pressure Independent Variable

39. Responding Variable (Dependent Variable) • The variable that is observed during the experiment Dependent Variable

40. For the results of an experiment to be accepted the experiment must produce the same results no matter how many times it is repeated or by whom

41. Theory • A broad and extensively tested explanation of why experiments give certain results. • A theory can NEVER be proven because a new experiment can always disprove it

43. Scientific Law • A concise statement that summarizes the results of many observations and experiments. • Scientific law describes natural phenomena without attempting to explain it

44. Qualitative Observation • Give results in a descriptive non-numerical form • Subjective • Ex. The solution is green, The precipitate is fluffy

45. Quantitative Observation • Gives results in a definite form • Numbers and units

46. Measurement • A quantity that has both a number and a unit • Measurements are only as exact as the instrument used to take it

47. International System of Units (SI) • Length = meter(m) • Mass = gram (g) • Temperature = kelvin (K) although often we will use Celsius • Time = second (s) • Amount of substance = mole (mol) • Volume = liter (L)

48. Prefixes • Mega (M) = 106 • Kilo (k) = 103 • Deci (d) = 10-1 • Centi (c) = 10-2 • Milli (m) = 10-3 • Micro (m) 10-6 • Nano (n) = 10-9 • Pico (p) = 10-12

49. Length • The distance between 2 points • Unit: meter (m)

50. Mass • The amount of matter an object has • Units: Grams • Measuring tools: Triple Beam Balance, Electronic scale, Analytical Scale