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Measurement/Calculation

Measurement/Calculation. Units of Measure. Metric System. based on powers of ten, so it’s easy to convert between units. Remember: KING HENRY DANCED BEFORE DAWN COUNTING MONEY Or KING HENRY DIED BY DRINKING CHOCOLATE MILK. Units. How to use. Right. Kilo. Hecto. Deka. BASE. Deci.

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Measurement/Calculation

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  1. Measurement/Calculation Units of Measure

  2. Metric System • based on powers of ten, so it’s easy to convert between units. • Remember: • KING HENRY DANCED BEFORE DAWN COUNTING MONEY • Or • KING HENRY DIED BY DRINKING CHOCOLATE MILK

  3. Units

  4. How to use Right Kilo Hecto Deka BASE Deci Centi Milli Left

  5. Examples Kilo Hecto Deka • 20 L= _______ mL • 7 kg = _______ mg • 90 mm = _______ cm • 223 mL = ________ L • 0.49 hm = ______ m BASE Deci Centi Milli 20 000 7 000 000 9.0 0.223 49

  6. SI base units

  7. SI derived units (derived units are calculated from base units)

  8. NOTE: • 1 cm3 IS EQUAL TO 1 mL!!! • And a cc is the same as a cm3

  9. Measurement/Calculation Scientific Notation/Accuracy &Precision

  10. Rules to putting into Sci Not • Must have a whole number between 1- 9 • If you move: • Decimal toLeft…exponent is Positive • Decimal to Right...exponent is Negative

  11. Examples • .0032 • 15 300 000 3.2 X 10-3 1.53 X 107

  12. Examples • 5.00 X 104 • 2.32 X10-3 50 000 5.00 0 0 .00232 0 0 2.32

  13. Addition/Subtraction • Make exponents the same by moving decimal place and changing exponent • Then add/subtract and put in correct Sci Not OR Type into your calculator Change mode to Sci

  14. EXP EXP EE EE Example 5.00 X 104 + .244 X 104 5.00 X 104 + 2.44 X 103  5.244X 104 OR Type into your calculator Enter 5.00 4 3 + 2.44

  15. Multiplication/Division • Multiplication • Multiply numbers • Add exponents • Division • Divide numbers • Subtract exponents • Then put back in correctscientific notation!

  16. EXE EXP EXP ENTER EE EE Example (5.44 × 107 g) ÷ (8.1 × 104 mol) = = 6.7 × 102 g/mol =0.67 X 103 g/mol Type on your calculator: 5.44 7 8.1 4 ÷ = 671.6049383 = 670 g/mol = 6.7 × 102 g/mol

  17. Accuracy and Precision • Accuracy: how close a measurement is to the true value (the “correct answer”) • Precision: how close a value is to other values in that series

  18. Are the following groups of measurements accurate, precise, both, or neither? • 1) Given: true mass of sample of zinc is 14.5 g • Measurements made: • 13.2 g, 15.6 g, 17.9 g, 12.0 g • Given: true volume of sample of water is 33.3mL • Measurements made: • 22.4 mL, 22.2 mL, 22.4 mL, 22.3 mL • 3) Given: true length of copper wire is 58.5 cm • Measurements made: • 58.4 cm, 58.5 cm, 58.5 cm, 58.4 cm

  19. Qualitative: a descriptive measurement (quality); does not involve numbers Quantitative: a numerical measurement (quantity)

  20. Measurement/Calculation Significant Figures

  21. Rules to Significant Figures • If it’s not 0, it counts. • Example • 743.44 • 24 5 2

  22. Rules to Significant Figures • 0’s in between significant figures count. • Example • 506 • 20405 • .707 3 5 3

  23. Rules to Significant Figures • All 0’s at the end past the decimal point count. • Example • 2.440 • 784.30 4 5

  24. Rules to Significant Figures • 0’s as placeholders don’t count. • Example • 440 • 0.09 2 1

  25. Alternative Way Atlantic (Absent) Pacific (Present)

  26. Pacific (Present) Atlantic (Absent) • If the decimal is present, start on the Pacific side at the first nonzero digit and count it and all the digits to the right of it. • If the decimal is absent, start on the Atlantic side at the first nonzero digit and count it and all the digits to the left of it.

  27. Adding/Subtracting • Add/Subtract First • The answer has only as many decimal places as the measurement having the least number of decimal places. • Example 190.2 g 65.291 g 12.38 g 267.871 g 1 3 2 267.9 g Answer should have 1 decimal place

  28. Multiplication/Division Mult/Divide First • The answer has only as many significant figures as the measurement with the least number of significant figures. • Example 13.78 g 11.3 mL 4 3 1.22 g\ml = 1.219469 g/mL Answer should have 3 significant figures

  29. 2 • 5 • 2 • Example • 15000 • 2030.0 • 0.0020

  30. Measurement/Calculation Density

  31. Density • Derived unit • g/mL or g/cm3 • Mass/Volume

  32. D. Density • An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass. GIVEN: V = 825 cm3 D = 13.6 g/cm3 m = ? WORK: m = DV m = (13.6 g/cm3)(825cm3) m = 11 220 g=11 200g

  33. WORK: V = m D V = 25 g 0.87 g/mL D. Density • A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid? GIVEN: D = 0.87 g/mL V = ? m = 25 g V = 28.74mL = 29 mL

  34. WORK: D = m V D = 5.6 g 3.4 mL D. Density • A marble has a mass of 5.6 g. It is placed in a graduated cylinder with 50.0 mL of water. The water level rises to 53.4 mL. What is the density of the marble? 3.4 mL GIVEN: D = ? V = 53.4-50 =3.4 mL m = 5.6 g D=1.647 g/mL = 1.6 g/mL

  35. Graphing Graphing is an important tool for expressing data so that it is easier to read and interpret Rules for graphing: --place the manipulated/independent variable (the one that was changed) on the x axis. --place the dependent/responding variable (the results of that change) on the y axis. (dry mix) DRY MIX y scale = largest y value – smallest y value x scale = largest x value – smallest x value # of lines on the y axis # of lines on the x axis The graph should cover at least ¾ of the grid

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