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Today’s Goals: Units Rounding Scientific Notation

Ch 2: Data Analysis. Today’s Goals: Units Rounding Scientific Notation. Data Analysis. SI Units : Système Internationale d’Unités – internationally standard units (basically metric units). Data Analysis. Other units:

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Today’s Goals: Units Rounding Scientific Notation

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  1. Ch 2: Data Analysis • Today’s Goals: • Units • Rounding • Scientific Notation

  2. Data Analysis • SI Units: SystèmeInternationaled’Unités – internationally standard units (basically metric units)

  3. Data Analysis • Other units: • Derived Units: Units which are not base units or are made up of several base units • Volume: the space occupied by an object (liters, milliliters, cm3) • Density: a ratio that compares the mass of an object to its volume (ex: g/cm3)

  4. Data Analysis • Density practice: 1) A 157 g metal has a volume of 26 mL. What is its density? 6.0 g/ml

  5. Data Analysis • A bit of practice with density… • A 81.3g block has a volume of 7.27 cm3. What is its density? • A 30g sample has a density of 10 g/mL. What is its volume? • An unknown substance with a volume of 51.2 cm3 has a density of 5.3 g/cm3. What is its mass? 11.2 g/cm3 3 mL 270 g

  6. The math of chemistry • Quantitative Data • Uses numbers • Requires calculations • There are rules for communicating accuracy (correctness)

  7. Rounding • Rounding Rules • Look at digit to right of needed place to determine rounding direction • 1-4 Round down, 5-9 round up • Numbers “before” the decimal - replace with zeros • Numbers “after” the decimal point - drop rounded digits

  8. Rounding • Rounding Practice • 55,120 to the hundreds place • 921,789 to the tens place • 15.045 to the tenths place • 0.008897 to the thousandths place 55,100 921,790 15.0 0.009

  9. Scientific Notation • Makes small and large numbers easier to work with • Let’s see it: 45,000,000,000 = 4.5 x 1010 • 0.00000432 = 4.32 x 10-6 • A number times 10 raised to a power • Must have one non-zero digit to the left of the decimal • Numbers larger than 1 have a (+) exponent • Numbers smaller than 1 have a (-) exponent

  10. Scientific Notation • Practice • 0.00563 in scientific notation • -102,101,700 in sci. not. • .0001278 in sci. not. • 7.8964 x 106 as a real number • 6.02 x 104 as a real number • -4.85x10-3 as a real number 5.63 x 10-3 -1.021017 x 108 1.278 x 10-4 7,896,400 60200 -0.00485

  11. Calculating with Scientific Notation • Do not write this: grab your calculator and practice! • When entering numbers in scientific notation • Do not use the “^” key • Do not type “x 10” • Do not use the “yx” key

  12. Calculating with Scientific Notation • To enter a number in scientific notation use the “exponent” key • “EE” or “E” • This replaces the “x10” • When writing the result returned from the calculator, always include the “x10” notation • 1.392 x 106 = 1.392E6 = 1392000 • 2.8 x 10-3 = 2.8E-3 = 0.0028

  13. Practice • Worksheet: Due tomorrow

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