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Chapter 2

Chapter 2. Sig figs and math Be sure to write all notes from class and problems -. Metric System King Henry Died –drinking choc milk. Kilo-k— 1000x Hecta -h- 100x Deka - da- 10X Deci -d- 1/10 Centi – c- 1/100 Milli - m - 1/1000 Micro- u - 1/1000000.

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Chapter 2

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  1. Chapter 2 Sig figs and math Be sure to write all notes from class and problems -

  2. Metric SystemKing Henry Died –drinking choc milk • Kilo-k— 1000x • Hecta-h- 100x • Deka- da- 10X • Deci-d- 1/10 • Centi – c- 1/100 • Milli- m - 1/1000 • Micro- u - 1/1000000

  3. International System of Units • SI is the abbreviation • Based on standards that never change

  4. Length Uses the meter Symbol m Based on the distance that light travels in a vacuum during a timed interval *2.54 cm = inch 1.6 km = mile

  5. Mass • Uses kilogram (we will use grams) • Symbol kg • Based on a Pt-Ir cylinder • 2.2 lb = kg • mass=amount of matter • Weight- gravitation pull on an object

  6. Time • Uses second • Abbreviation s ( or sec) • Based on the radiation emitted by a Cs-133 sample • 60 s = min 60 min= hour

  7. Derived units • A combination of base units • Density= mass / volume • Volume = length x width x height • cm3 = mL • Water only density is equal to 1.00 g/mL

  8. Bouyant- float- density is less than 1.0g/ml • Sink- density is greater than 1.0g/mL • Meniscus- curve of the liquid– read the bottom for water

  9. Temperature and Heat • Heat is the total Kinetic energy and is dependent upon mass- Measured in Joules • Temperature is the average Kinetic energy- uses a temperature scale

  10. Temperature • Measure in celcius • Kelvin- based on absolute zero (particles are motionless) • Convert to Kelvin C + 273 = kelvin K- 273 = C

  11. Energy • Energy is measured in Joules • 4.184 Joules = calorie • 1000 calories = 1 Calorie • Calorie is the unit used in food descriptions

  12. Specific Heat • Specific Heat is the heat needed to raise 1 gram of a substance 1 degree C • Formula: • C- Specific Heat Capacity m- mass t – change in temperature

  13. Accuracy and Precision • Precision- value repeats • Accuracy- closeness to accepted value • Percent error= Exp- theoreticalx 100 • Theoretical

  14. Accuracy and PrecisionProblems • The product had a mass of .125g. The known value was .130g. What is the %error? (must write formula)

  15. Significant Figures sig figs • All certain digits and 1 estimated • (Under the files on my website are some rules if needed)

  16. Conversion factors are NOT considered when determining the number of sig figs

  17. Multiply or Divide • The answer should contain the lowest number of sig figs in the problem

  18. Add or Sub • The final digit is in the same place as the left most sig fig

  19. Scientific notation • We reviewed this in class- come by if you need help

  20. Factor Label • Conversion factors are used to change from one unit to another. • Ex- dozen=12 • foot=12 inches • 2 pints = quart • 2.54 cm = inch • 2.2 pounds=kilogram • 1.6 Km = mile • 5280ft=mile

  21. mole • Mole is a counting unit used in chemistry • Mole = 6.02 x 1023 atoms, particles A mole allows for comparisons to be made between elements or compounds.

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