2. Introduction to Chemistry

5. http://www.youtube.com/watch?v=izeuGr 0lbN0 http://www.youtube.com/watch?v=izeuGr 0lbN0 http://www.youtube.com/watch?v=izeuGr 0lbN0 http://www.youtube.com/watch?v=izeuGr 0lbN0

6. What is Chemistry? The study of the composition of matter and the changes that matter undergoes The study of the composition of matter and the changes that matter undergoes

7. Five major branches of chemistry Organic Organic

8. Inorganic Inorganic

9. Analytical Analytical Physical Physical Biochemistry Biochemistry

10. Why study Chemistry??? Pure Chemistry Pure Chemistry Applied Chemistry (Technology) Applied Chemistry (Technology)

11. Chemistry plays a big part in our lives We are in the “Age of Plastics” We are in the “Age of Plastics” High “strength to weight” ratio High “strength to weight” ratio

12. Energy New fuels New fuels New insulation material New insulation material

13. Energy from the sun Energy from the sun Hydrogen cells Hydrogen cells Storage batteries Storage batteries

14. Medicine and Biotechnology Medicines Medicines Surgical breakthroughs Surgical breakthroughs Genetic research Genetic research

15. Agriculture Protect crops Protect crops Increase food supply Increase food supply Increase strength and vitality of plants Increase strength and vitality of plants

16. Environment Pollution Pollution Catalytic converters Catalytic converters Acid rain Acid rain Ozone layer Ozone layer

17. SCIENTIFIC METHOD

18. 1. Observation Gather data: qualitative or quantitative

19. 2. Hypothesis t tentative explanation for what is observed (educated guess)

20. 3. Experiments – set of controlled observations that test a hypothesis

21. –Independent variable – one you are going to change

22. –Dependent – changes depending on the independent variable

23. –control – standard for comparison –Model – visual, verbal and/or mathematical explanation of experimental data

24. Conclusion – judgment based on the information obtained – judgment based on the information obtained

25. Theory – explanation that has been supported by MANY experiments – explanation that has been supported by MANY experiments

26. Scientific Law – describes a relationship in nature that is supported by many experiments. – describes a relationship in nature that is supported by many experiments.

27. Types of observations Qualitative observations – describe a substance without using numbers “It is heavy” “ It is blue” “It smells”

28. Quantitative observations – use numbers 87 millimeters 10 liters 4.0 g/ml

29. Scientific Notation 765,000,000,000 7.65 X 10 11 Move decimal to the left – is positive 0.0000084 8.4 X 10 -6 Move decimal to the right – is negative Samples on handout

30. Write in standard notation 4.5 x 10 -5 0.000045 3.42 x 10 4 34200

31.  Is how close a measurement is to the correct or accepted value

32.  How close a series of measurements are to each other  (how close a measurement is to other measurements of the same thing)  Dartboard example

33.  Assures the certainty of measurements  For any measurement, scientists only record all the digits they are certain of, plus one estimated figure  Together, they are called “significant figures”

34. Sample 6.2345 meters All the digits are significant. Which one is the estimated and which are certain? 6,2,3,4 are certain 5 is estimated

35.  A scientist measures 89 seconds  All are significant  Which are certain and which are estimated?  8 is certain  9 is estimated

36. R ULES FOR COUNTING SIGNIFICANT FIGURES IN A MEASUREMENT Rule 1 – all nonzero digits are significant – 1,2,3,4,5,6,7,8,9 – are significant Rule 2 – Final zeroes to the right of the decimal point are significant 3.4000 5 sig figs

37. Rule 3 – zeroes between two significant digits are significant 304 3 sig figs 70009 5 sig figs

38.  Rule 4 – zeroes used for spacing the decimal point are not significant  0.00045 2 sig figs  0.02387 4 sig figs

39.  Rule 5 – for numbers in scientific notation, all of the digits before “x 10 x ” are significant  5.730 x 10 9 4 sig figs

40.  7000 1 sig fig  7000. 4 sig figs

41. Let’s practice!! 135.3 4 sig figs 4.6025 5 sig figs 200,035 6 sig figs 0.0000300 3 sig figs

42. 2.0000300 8 sig figs 0.002 1 sig fig 4.44 x 10 3 3 sig figs 2.0 x 10 -2 2 sig figs

43. 10.00 4 sig figs 10 1 sig fig 102,000 3 sig figs

44. Solving problems with sig figs Multiplying and dividing with sig figs The answer you get must be rounded to the same number of sig figs as the measurement with the lowest number of sig figs (that you multiplied or divided)

45. Example Multiply 4.610 feet by 1.7 feet. Express your answer in correct sig figs 4.610 x 1.7 = 7.837 How do you round it? 4.610 has 4 sig figs 1.7 has 2 sig figs Round answer to 2 sig figs Answer = 7.8 square feet

46. Divide 653 miles by 3 hours. Express in the correct number of sig figs Answer = 200 miles/hour

47. Adding and Subtracting with sig figs When adding or subtracting measurements, the answer cannot have more certainty than the least certain measurement. Answer must have the same number of sig figs to the right of the decimal point as the measurement with the fewest sig figs to the right of the decimal point

48. Example 4.271 grams (3 sig figs to the right of decimal) 2 grams (0 sig figs to the right of decimal) + 10.0 grams (1 sig fig to the right of decimal) 16.271 grams  round 16 grams

49. Sample Add these measurements: 4.35 seconds and 212.2 seconds. Express your answer using correct sig figs Answer = 216.6 seconds Add these measurement: 2.423 meters + 0.001365 meters Answer = 2.424 meters

50. Measurement units and unit conversions Common metric base units: Distance or length – meter m Mass – gram g Volume – liter L Temperature – degree Celsius o C Time – second s Also use Kelvin (K) for temperature

51. Metric Prefixes

52. Common metric prefixes Micro Example 1 μm = 0.000001 m 1 x 10 6 μm = 1 m

53. milli m 0.001 or (1 x 10 -3 ) Example 1 mg = 0.001 g 1000 mg = 1 g

54. centi c 0.01 or ( 1 x 10 -2 ) Example 1 cm = 0.01 m 100 cm = 1 m

55. Deci d 0.1 or (1 x 10 -1 ) Example 1 dL = 0.1 L (liter) 10 dL = 1 L

56. kilo k 1000 or (1.0 x 10 3 ) Example 1000 g = 1 kg

57. Unit Conversions Also called “factor labeling” How many inches in 2 feet? How many feet in 36 inches? You just did a unit conversion!!!!!! Look at board

58. Must use correct “conversion factor” 230 cm = ? m Must know that 100 cm = 1m Write possible conversion factors 1m or 100 cm 100 cm 1 m

59. Write the number you are converting first Multiply it by the conversion factor that has the unit you want your answer to be in on the TOP This guarantees that you will divide or multiply when you are supposed to.

60. 230 cm x 1 m = 2.3 m 100 cm The top and bottom units cancel out and the only unit left is the one you want you answer to be in!!!!!

61. Text – practice on pgs. 36 -37 Show you two step conversions on board 4500 cm = ? km

62. Derived units What does “derived” mean? A derived unit is a measurement unit created by multiplying or dividing other units Miles per hour words per minute

63. Area Length x width ft x ft = ft 2 ft 2 is a derived unit (derived from two length units) m x m = m 2 m 2 is a derived unit (derived from two length units)

64.  Length x width x height  ft x ft x ft = ft 3  m x m x m = m 3  cm x cm x cm = cm 3

65.  Describes how dense something is  How heavy it is for its size  Density = mass divided by volume  D = M  V  M = D x V  V = M  D

66.  Since you are dividing two different measurements, the unit for density is a DERIVED UNIT.  Derived from a mass measurement and a volume measurement  g/mL  g/L

67.  Calculate the density of a substance with a mass of 24.3 g and a volume of 32.9 mL. Use the correct unit and the correct number of sig figs in your answer.  D = M  V  D = 24.3 g  32.9 mL  Ans. = 0.739 g/mL

68.  What is the volume of an object with a density of 1.25 g/mL and a mass of 281 g?  V = M  D  V = 281 g  1.25 g/mL  g cancels, so units are mL for answer  V = 225 mL

69.  Text – Pg. 46 #20, 21  Pg. 47 #25