Unit 1

1. Unit 1 Matter and Measurements Honors Chemistry

2. How to be Successful in Chemistry • Memorize strategies not equations! • Study a lot! • Work ALL the problems. • Self-evaluate after test results. • Make use of Tutorial. • Start a Study Group Wolpa/Advanced Placement Chemistry

3. Chapter 1: Matter and Measurement Overview: • The Study of Chemistry • Classifications of Matter • Properties of Matter • Units of Measurement • Uncertainty in Measurement • Dimensional Analysis • Basic Math Concepts Wolpa/Advanced Placement Chemistry

4. Chemistry • The study of matter and the changes it undergoes Wolpa/Advanced Placement Chemistry

5. Matter • Anything that has mass and occupies space • Characterized by physical and chemical properties • Law of the Conservation of Mass - matter is neither created nor destroyed in chemical reactions Wolpa/Advanced Placement Chemistry

6. Element • An element is a pure substance composed of one type of atom. • An atom is the smallest particle of an element that retains the chemical properties of the element. • An element is the most basic form of matter under ordinary circumstances • Simplest chemical substance • Only a few elements are found in their free state (nitrogen, oxygen, gold, etc.) Wolpa/Advanced Placement Chemistry

7. Elements and the Periodic Table • Each element is represented by a name and a symbol. (Periods/groups - alkali metals, alkaline earth metals, halogens, noble gases) • The first letter is always capitalized the second (and third) are never capitalized. Wolpa/Advanced Placement Chemistry

8. Compound • A unique substance composed of two or more elements that are chemically combined (i.e. joined intimately, not just mixed together) • Pure compounds have definite compositions and properties • Require complex chemical procedures to separate into simpler substances (elements) • Compounds include water, table salt, sugar, etc Wolpa/Advanced Placement Chemistry

9. Properties of Substances • Elements and Compounds are pure substances. • Properties describe the particular characteristics of a substance • Pure substances have definite composition and definite, unchanging properties • Physical properties - can be observed without changing the substance • Chemical properties - require that the substance change into another Wolpa/Advanced Placement Chemistry

10. Physical States • The three physical states are solid, liquid and gas • solids - have a definite shape and volume • liquid - have a definite volume but not a definite shape • gas - neither a definite volume or shape • A substance exists in a particular physical state under defined conditions Wolpa/Advanced Placement Chemistry

11. Wolpa/Advanced Placement Chemistry

12. Phase Changes • Melting point or freezing point • temperature at which a substance changes from solid to liquid • Boiling point or condensation point • temperature at which a substance changes from liquid to gas Wolpa/Advanced Placement Chemistry

14. More on Evaporation…. • Liquid evaporates faster when heated. This is because heating a liquid increases the average kinetic energy of its particles. • As evaporation occurs, the particles with the highest kinetic energy escape first. • Evaporation is a cooling process!!

15. Boiling Pointvapor pressure = external pressure • When a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to boil. • Because atmospheric pressure is lower at higher altitudes, boiling points decrease at higher altitudes.

17. Phase Diagram Cont… • The Triple Point describes the only set of conditions at which all three phases can exist in equilibrium with one another. • A decrease in pressure lowers the boiling point and raises the melting point • An increase in pressure will raise the boiling point and lower the melting point.

18. Density • ratio of the mass of a substance to the volume of that mass • usually measure in g/mL for solids and liquids; g/L for gases • also a conversion factor relating the mass of a substance to it’s volume • Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water Wolpa/Advanced Placement Chemistry

19. What’s happening? Wolpa/Advanced Placement Chemistry

20. Density Calculation • Equation d=m/V • Example: If an object has a mass of 15.0 g and a volume of 10cm3 what’s the objects density? d = 15.0 g/ 10.0 cm3 = 1.50 g/cm3 Wolpa/Advanced Placement Chemistry

21. Temperature and its Measurement • Temperature - measure of the intensity of the heat of a substance • Thermometer - device to measure temperature • Kelvin - K - SI unit of temperature • Celsius - °C - commonly used unit • Fahrenheit - °F - only used in USA Wolpa/Advanced Placement Chemistry

22. Relationships between temperature scales Wolpa/Advanced Placement Chemistry

23. The Kelvin scale • The idea of negative temperatures is a problem for any mathematical treatment of temperature dependent properties. • It was found that a practical minimum temperature did exist (absolute zero) which has a value of -273.15°C • This is defined as 0 K (no degree sign) • The Kelvin degree is the same size as the Celsius degree (K = °C + 273.15) Wolpa/Advanced Placement Chemistry

24. Temperature Scale Comparison Wolpa/Advanced Placement Chemistry

25. Chemical Properties • Chemical properties - involve how a substance changes into another • Sometimes quite difficult to determine • Some examples are burning (as opposed to boiling) and color changes Wolpa/Advanced Placement Chemistry

26. ? A mixture is a combination of two or more substances in which the substances retain their distinct identities. • Homogenous mixture – composition of the mixture is the same throughout. • Heterogeneous mixture – composition is not uniform throughout. Wolpa/Advanced Placement Chemistry

27. Mixtures • Combinations of two or more substances • Can be separated by exploiting different physical properties (filtration, distillation, crystallization, chromatography) • Have chemical and physical properties that are different from the substances that make them up • The percentages by mass of the components of a mixture can be varied continuously Wolpa/Advanced Placement Chemistry

28. Heterogeneous Vs. Homogeneous Mixtures Wolpa/Advanced Placement Chemistry

29. Physical means can be used to separate a mixture into its pure components. Wolpa/Advanced Placement Chemistry

30. magnet distillation filtration Physical means can be used to separate a mixture into its pure components. (Mechanical process) Wolpa/Advanced Placement Chemistry

31. Physical Change: the composition of the substance remains the same but the state changes. Wolpa/Advanced Placement Chemistry

32. Chemical Change: a new substance is formed. Wolpa/Advanced Placement Chemistry

33. Physical Properties: Identifying properties of a substance. • Density • Solubility • Color • Melting/Boiling Point • Crystalline Shape • Malleability, Ductility, Conductivity, Luster • Etc. Wolpa/Advanced Placement Chemistry

34. Extensive and Intensive Properties An extensive property of a material depends upon how much matter is is being considered. • mass • length • volume An intensive property of a material does not depend upon how much matter is is being considered. • density • malleability • color Wolpa/Advanced Placement Chemistry 1.6

35. Solutions • A type of homogeneous mixture • Usually involves a liquid phase, but can be solid-solid, liquid-liquid, solid-liquid, etc. • The pure substances can be in different phases but form a homogeneous mixture (table salt and water, for example) Wolpa/Advanced Placement Chemistry

36. Alloys • important solid solutions of two or more metals • dental fillings (silver and mercury) • stainless steel (iron, chromium and nickel) Wolpa/Advanced Placement Chemistry

37. Putting it All Together Wolpa/Advanced Placement Chemistry

38. Measurements and Units Measurement - determines the quantity, dimensions or extent of something 1.Consist of two parts a. a numerical quantity (1.23) b. a specific unit (meters) Unit - a definite quantity adapted to as a standard of measurement Wolpa/Advanced Placement Chemistry

39. Features of Measured Quantities When we measure a number, there are physical constraints to the measurement Instruments and scientists are not perfect, so the measurement is not perfect (i. e., it has error) The error in the measurement is related to the accuracy and the precision of the measurement Wolpa/Advanced Placement Chemistry

40. Accuracy and Precision Accuracy – how close the measurement is to the “true” value (of course we have to know what the “true” value is) Precision - the degree to which the measurement is reproducible 1. expressed through how we write the number – significant figures Wolpa/Advanced Placement Chemistry

41. Example: Accuracy and Precision Wolpa/Advanced Placement Chemistry

42. Equations for Precision and Accuracy 1. Precision Percent Relative error % RE = Avg. Dev / Avg Value X 100 2. Accuracy Absolute Error % AE = (True value-Avg Value) X 100 True Value Wolpa/Advanced Placement Chemistry

43. Significant Figures • Any digit that is not zero is significant • 1.234 kg 4 significant figures • Zeros between nonzero digits are significant • 6006 m 4 significant figures • Zeros to the left of the first nonzero digit are not significant • 0.08 L 1 significant figure • One or more final zeros to the right of the decimal point are significant • 2.00 mg 3 significant figures • 0.00420 g 3 significant figures • 10.006000 8 sig figs Wolpa/Advanced Placement Chemistry

44. Counting Significant Figures Atlantic / Pacific Method a. Absent Decimal- Start on “atlantic” side of number & cross out all zeroes until 1st nonzero digit is reached, remaining digits are significant b. Present decimal- start on the “pacific” side of the number & cross out all zeros until the 1st nonzero digit Is reached, remaining digits are significant Wolpa/Advanced Placement Chemistry

45. 2. Examples: Wolpa/Advanced Placement Chemistry

46. How many significant figures are in each of the following measurements? 24 mL 2 significant figures 4 significant figures 3001 g 0.0320 m3 3 significant figures 6.400 x 104 molecules 4 significant figures 560 kg 2 significant figures Wolpa/Advanced Placement Chemistry

47. 89.332 + 1.1 one significant figure after decimal point two significant figures after decimal point Number is rounded to “tens” place 90.432 round off to 80 round off to 90.4 round off to 0.79 3.70 -2.9133 0.7867 Significant Figures Addition or Subtraction The answer cannot be more accurate than any of the original numbers. 370 -291.33 78.67 Wolpa/Advanced Placement Chemistry

48. 3 sig figs round to 3 sig figs 2 sig figs round to 2 sig figs Significant Figures Multiplication or Division The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x 3.6666 = 16.536366 = 16.5 6.8 ÷ 112.04 = 0.0606926 = 0.061 Wolpa/Advanced Placement Chemistry

49. 6.64 + 6.68 + 6.70 = 6.67333 = 6.67 = 7 3 Significant Figures Exact Numbers Numbers from definitions or numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? Because 3 is an exact number Wolpa/Advanced Placement Chemistry

50. Scientific notation -Expressing very large and small numbers Using scientific Notation - Numbers are expressed with one nonzero digit to the left of the decimal point multiplied by 10 raised to an appropriate power 1. The base is the number with all of the appropriate significant digits 2. The exponent is the power of ten the base is multiplied by Wolpa/Advanced Placement Chemistry