1 / 53

Chapter 2

Chapter 2. The Numerical Side of Chemistry. Objectives. Recall SI Base Units Determine units for calculations Compare accuracy and precision Calculate percent error Determine the number of SF Perform calculations using SF. Units of Measure. SI Base Units Mass Kilogram – kg

emera
Download Presentation

Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 2 The Numerical Side of Chemistry

  2. Objectives • Recall SI Base Units • Determine units for calculations • Compare accuracy and precision • Calculate percent error • Determine the number of SF • Perform calculations using SF

  3. Units of Measure • SI Base Units • Mass • Kilogram – kg • 1 kilogram is about 2.20 pounds • Length • Meter – m • 1 meter is about 3 feet • Time • Second – s • About a second!

  4. Base Units cont. • Temperature • Kelvin – K • 273 K = 0 degrees C • Amount • Mole – mol • 1 mol = 6.022x1023 particles

  5. Base Units cont • Current • Ampre – A • Luminous Capacity • Candela – cd • First five are the most commonly used in chemistry

  6. Derived Units • Combinations of base units • Speed is meters/second • Volume is m3 • Density is kg/m3

  7. Units in Calculations • (12.0m) * (12.0m) = 144 m2 • (22.0m) / (11.0s) = 2.00 m/s • ((5.00kg) (4.00m)) / ((5.00s)(2.00s)) • = 2.00 kg*m/s2 or 2.00 N

  8. Precision and Accuracy • Accuracy • The nearness of a measurement to its accepted value • Precision • The agreement between numerical values • You can be precise without being accurate

  9. Accuracy and Precision What does each represent? • Neither • Precise • Both

  10. Percent Error or (Relative Error) • Tells what percent you are wrong • Ex. A 95% on a test is a 5% error

  11. What’s the Length?

  12. Uncertainty in Measurement • Some uncertainty is present in all measurement • No measurement has an infinite number of decimal places • Measurements include all known digits plus one estimated digit • SIGNIFICANT FIGURES

  13. Significant Figures • Rule #1 • All Nonzero digits are significant • Ex. 34.22 mL • 4 Significant Figures (SF) • Ex. 122.89 s

  14. Significant Figures • Rule #2 • “Captive Zeros” • Zeros appearing between nonzero digits are significant • Ex. 405.3004 g

  15. Significant Figures • Rule #3 • “Leading Zeros” • Zeros appearing in front of nonzero digits are not significant • 0.02024 g

  16. Significant Figures • Rule #4 • “Ending Zeros” • Ending zeros are significant if there is a decimal place • 23.00 m • 40000. m • 40000 m

  17. What is the length?

  18. Significant Figures • Rule #5 • “Exact Numbers” • Exact number have an unlimited number of significant figures • Exact numbers are counting numbers or definitions • 2 cars or 1000g/1kg

  19. Significant Figures • Rule #6 • “Scientific Notation” • All numbers that come before the x10n are significant • Must be in proper form • 3.33x105 • 2.04x10-4

  20. Rounding • 5 and larger round up • 4 and smaller round down • Round the following • 34.567 to 2 SF = • 756.44 to 4 SF = • 0.004325 to 3 SF = • 3436543 to 2 SF =

  21. Calculations using SF’s • Addition and Subtraction • The answer must have the same number of digits to the right of the decimal as there are in the measurement having the fewest digits to the right of the decimal point • WHAT!!!! • Ex. 12.11 m + 15.3 m = • Number of SF’s does not matter!

  22. Calculations using SF’s • Multiplication and Division • The answer can have no more SF’s than are in the measurement with the fewest total SF’s • Ex. 55 m / 11.34 s =

  23. Scientific Notation • A method of representing very large or very small numbers • M x 10n • M is a number 1 or larger and less than 10 • n is an integer (positive or negative) • All digits in M are significant (If in proper form)

  24. Converting to Sci. Notation • Move decimal so that M is between 1 and 10 • Determine n by counting the number of places the decimal point was moved • Moved to the left, n is positive • Moved to the right, n is negative

  25. Sci. Notation Examples • 340,000,000 = • 5.04x105 = • 0.00000300 = • 2.212x10-4 =

  26. Sci Notation on Calculators • Enter digits in you calculator using the EE key. • For TI 83’s it is the 2nd of the comma • For TI 30’s it is a key • Saves key strokes • Fewer OOR mistakes • 3.4x106 = 3.4E6 • 7.4x10-5 = 7.4E-5

  27. Math Operations • Multiply and Divide • Multiply or divide first number • Add exponents (Multiply) • Subtract exponents (Divide) • Addition and Subtraction • Exponents must be the same • Then add or subtract first number • Exponents stay the same

  28. Calculations • 3.0x105 + 4.0x105 = • 4.0x103 – 2.0x102 = • 7.0x105 * 2.0x104 = • 8.0x106 / 4.0x10-3 = • _____4.5x104____ = 6.2x106 * 3.1x10-8

  29. Objectives • Recall metric prefixes • Convert numbers within the metric system • Convert numbers between metric and nonmetric units

  30. Metric System • Decimal system • Based on multiples of 10 • SI Prefixes • Used to easily deal with large and small numbers

  31. SI Prefixes (10x larger) • Tera • Giga • Mega • Kilo • Hecto • Deca • Base • T • G • M • k • h • da • 1012 • 109 • 106 • 103 • 102 • 101 • 100 • 1000000000000 • 1000000000 • 1000000 • 1000 • 100 • 10 • 1

  32. SI Prefixes (10x smaller) • Base • Deci • Centi • Milli • Micro • Nano • Pico • 1 • .1 • .01 • .001 • .000001 • .000000001 • .000000000001 • 100 • 10-1 • 10-2 • 10-3 • 10-6 • 10-9 • 10-12 • d • c • m • μ • n • p

  33. Relationships • SOOOOOO • 1000 mm equals a m • 100 cm equals a meter • 100 m equals a hm • 1x106 mol equals a Mmol • 1x109 nm equals a m

  34. Conversions • Changing one unit to another • Use conversion factors • Statements that are true • Ratios of equality • Many on your periodic table • Examples • 1 inch = 2.54 centimeters • 1 meter = 39.4 inches

  35. Metric Conversion Factors • Set up ratios that are true • Make the larger unit be 1 • Ratios can be flipped

  36. Convert 67 kg to g

  37. Convert 450 cL to dL

  38. Convert 3.4x108 ng to kg

  39. Other Conversions • Set up conversion factor to be true • Take equality from a given • Periodic Table Back

  40. Cont. • Make sure all the units cancel • Watch out for m/s or m2 • One special conversion for water • 1mL liquid water = 1 g = 1cm3 • Due to density

  41. Convert 763 cm to yd

  42. Convert 1.2 mi/hr to ft/s

  43. Convert 3.8 m/hr to cm/s

  44. Objectives • Describe density • Perform calculations using density

  45. Density • Ratio of mass to volume • Density = __Mass__ Volume • Units • Solids – g/cm3 • Liquids – g/mL • Gases – g/L

  46. Density • Mass is determined on a balance • Volume is measured in two ways • Regular objects can be measured • All objects can use water displacement

  47. Density • Physical Property • Can be used to identify a substance Lead 11.35 Iron 7.87 Magnesium 1.74 Zinc 7.13 Copper 8.96

  48. Rearranging the Equation • Density equation can be rearranged • Solve for mass • Solve for volume

More Related