Chapter 2.2 : Units of Measurement

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  • 1. UNITS OF MEASUREMENT
    SECTION 2-2
  • 2. Objectives
    Distinguish between a quantity, a unit, and a measurement standard
    Name SI units for length, mass, time, volume, and density
    Distinguish between mass and weight
    Perform density calculations
    Transform a statement of equality to a conversion factor
  • 3. Units of measurement
    Quantity – magnitude, size, or amount
    5 2,000,000 0.030o
    • Units – compare what is measured with defined size
    • 4. mL g feet
    • 5. Quantity has no meaning without the unit
    • 6. 5 mL 100 g 2,000,000 feet
  • SI Measurement
    Le Systeme International d’Unites
    Adopted 1960 as world-wide agreed upon standards
    • Base units
    • 7. length meter m
    • 8. mass kilogram    kg
    • 9. time second s
    • 10. temperature  kelvin K
    • 11. amount of substance mole mol
    • 12. Volume Liters L
  • Some SI Base Units
    Mass – measure of the amount of matter in an object
    Grams (g)
    Electronic scale or triple beam balance
    • Volume – amount of space an object takes up
    • 13. Liters L
    • 14. V = L X W X H (cm3)
    • 15. Graduated cylinder
    • 16. Water displacement
    • 17. Weight – measure of the gravitational pull on matter
    • 18. Example : Moon has 1/6 weight
  • Metric Prefixes
    Tera- T 1012 1 000 000 000 000
    Giga- G 109 1 000 000 000
    Mega- M 106 1 000 000
    kilo- k 103 1000
    hecto- h 102 100
    deka- da 10 10
    - - - -
    deci- d 10-1 0.1
    centi- c 10-2 0.01
    milli- m 10-3 0.001
    micro- u (mu) 10-6 0.000 001
    nano- n 10-9 0.000 000 001
    pico- p 10-12 0.000 000 000 001
  • 19. Derived SI units
    Combination of SI base units
    Examples
    Area m2 L x W
    Volume m3 L x W x H
    Density Kg/m2 mass/volume
    Molar mass Kg/mol mass/mole
  • 20. Volume and Density
    Volume = Length x Width x Height
    1 cm x 1 cm x 1 cm = cm
    • Density = mass / Volume
    Sample Problem 2-1
    A sample of aluminum metal has a mass of 8.4 g. The volume of the sample is 3.1 cm3. Calculate the density of aluminum.
  • 21. Density of Some Common SubstancesSubstanceDensity(g/cm3)
    Air 0.0013
    Feathers 0.0025
    Wood(Oak) 0.6 - 0.9
    Ice  0.92 
    Water  1.00
    Bricks  1.84
    Aluminum  2.70
    Steel  7.80
    Silver  10.50
    Gold  19.30 
  • 22. Conversion Factors
    Ratio derived from the equality between two different units that can be used to convert from one unit to the other
    • Equalities
    • 23. 1 dollar = 4 quarters
    • 24. 1 kg = 1000 g
    • 25. 1 Km = 0.6213 miles
    1 dollar4 quarters
    4 quarter or 1 dollar
  • 26. Making conversions
    How many miles are in 15 Km?
    Write given value:
    Choose conversion factor
    Multiply top and divide bottom
    15 Km x 0.6213 miles = 9.3 miles
    1 Km