Introduction to Chemistry

1. Introduction to Chemistry

4. http://www.youtube.com/watch?v=izeuGr0lbN0

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

6. Five major branches of chemistry • Organic

7. Inorganic

8. Analytical • Physical • Biochemistry

9. Why study Chemistry??? • Pure Chemistry • Applied Chemistry (Technology)

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

11. Energy • New fuels • New insulation material

12. Energy from the sun • Hydrogen cells • Storage batteries

13. Medicine and Biotechnology • Medicines • Surgical breakthroughs • Genetic research

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

15. Environment • Pollution • Catalytic converters • Acid rain • Ozone layer

16. SCIENTIFIC METHOD

17. 1. Observation Gather data: qualitative or quantitative

18. 2. Hypothesis • tentative explanation for what is observed (educated guess)

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

20. Independent variable – one you are going to change

21. Dependent – changes depending on the independent variable

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

23. Conclusion • – judgment based on the information obtained

24. Theory • – explanation that has been supported by MANY experiments

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

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

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

28. Scientific Notation • 765,000,000,000 • 7.65 X 1011 • Move decimal to the left – is positive • 0.0000084 • 8.4 X 10-6 • Move decimal to the right – is negative • Samples on handout

29. Write in standard notation • 4.5 x 10-5 • 0.000045 • 3.42 x 104 • 34200

30. Accuracy • Is how close a measurement is to the correct or accepted value

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

32. Significant figures • 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”

33. 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

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

35. Rules 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

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

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

38. Rule 5 – for numbers in scientific notation, all of the digits before “x 10x” are significant • 5.730 x 109 4 sig figs

39. Be careful of this one • 7000 1 sig fig • 7000. 4 sig figs

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

41. 2.0000300 • 8 sig figs • 0.002 • 1 sig fig • 4.44 x 103 • 3 sig figs • 2.0 x 10-2 • 2 sig figs

42. 10.00 • 4 sig figs • 10 • 1 sig fig • 102,000 • 3 sig figs

43. 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)

44. 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

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

46. 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

47. 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

48. 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

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

50. Metric Prefixes