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PowerPoint on Measurement

PowerPoint on Measurement

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  • 1. Measurement How much? How long? How many?
  • 2. Exact and inexact numbers
    • Exact number:
      • A number with no uncertainty it
      • A dozen donuts, seven students, etc.
    • Inexact number:
      • A number that has a degree of uncertainty in it; results anytime a measurement is made
      • Height of student; temperature of student
  • 3. Precision and Accuracy
    • Accuracy:
      • How close a measured value is to the actual (true) value
    • Precision:
      • How close the measured values are to each other
  • 4. Testing our knowledge
    • How accurate?
      • Low accuracy
    • How Precise?
      • High precision
  • 5. Testing our knowledge
    • How accurate?
      • High accuracy
    • How Precise?
      • Low precision
  • 6. Testing our knowledge
    • How accurate?
      • High accuracy
    • How Precise?
      • High precision
  • 7. Systems of Measurement
    • English:
      • Commonly used in commerce and homes
        • Inch, foot, pound, quart, and gallon
    • Metric system
      • Used worldwide
    • SI system
      • Revised in 1960 with improved units
      • SI stands for “French Systeme International d’Unites”
      • Used by scientists
  • 8. SI System
    • The Seven Base Units in the SI system:
    cd candela Luminous intensity A ampere Electric current m mole Amount of substance K kelvin Temperature s Second Time kg Kilogram Mass m Meter Length Unit Abbreviation Unit Name Base quantity
  • 9. Metric system prefixes
    • Common prefixes
    • For example,
      • 100 cm = 1 m
      • 1,000 mg = 1 gm
    1/1,000 m Milli 1/100 c Centi 1/10 d Deci 1,000 k Kilo
  • 10. Length
    • Meter is the SI base unit of length
      • 1 meter=1.05 yards
      • A dime is about 1 mm thick
        • Or…1/1000 of a m
      • Your little finger is about 1 cm across
        • Or…1/100 of a m
  • 11. Mass vs. Weight
    • Mass
      • A measure of the total quantity of matter in an object
    • Weight
      • A measure of the force exerted on an object by gravitational forces
      • If you weigh 60 kg on Earth, will you weigh more or less on the moon? Why?
  • 12. Mass vs. Weight
    • How much does this astronaut floating in space weigh?
    What is the astronaut’s mass?
  • 13. Mass
    • Kilogram is the SI unit for mass
      • Note that the prefixes are added to gram not kilogram, i.e., centigram, milligram, etc.
      • 10 pennies weigh about 1 gram
        • 1 gram is 1/1,000 kilogram
      • Aspirin commonly is 325 mg
        • 1 milligram = 1/1000 gram
  • 14. Area and volume
    • Area: measure of extent of a surface
      • For a square, length vs width
        • Square feet, ft 2
        • Square cm, cm 2
    • Volume: measure of the amount of space occupied by an object
      • For a cube, side x side x side
        • Cubic feet, ft 3
        • Cubic cm, cm 3
  • 15. Volume
    • Cubic meter (m 3 ) is the SI system base unit for volume
      • A m 3 is too large to be used in the chemistry lab, so cm 3 is much more common
      • 1 cubic cm (cm 3 )= 1 milliliter (ml)
      • 1 liter is a volume equivalent to that of a cube that is
        • 10 cm x 10 cm x 10 cm or 1,000 cm 3
  • 16. SI Units
    • The best way to understand SI units is to use them in everyday life
    • Everyday examples
  • 17. Measuring volume
    • Technique for measuring volume
  • 18. Temperature
    • A measure of the hotness or coldness of an object
    • Three scales:
      • Kelvin
        • after William Kelvin (1824-1907)
        • Does not use degree symbol
      • Celsius
        • After Anders Celsius (1701-1744)
        • Most commonly used in science
  • 19. Three scales
    • Kelvin
      • after British mathematician and physicist, William Kelvin (1824-1907)
      • Does not use degree symbol
      • No negative numbers
    • Celsius
      • after Swedish astronomer, Anders Celsius (1701-1744)
      • Most commonly used in science
    • Fahrenheit
      • After German physicist, Gabriel Fahrenheit (1686-1736)
      • Based on the temperature of a salt-ice mixture as 0 °F and the boiling point of mercury at 600 °F
  • 20. Common temperatures
    • Freezing point of water
      • 0 °C=32°F=273.15 K
    • Room temperature
      • 22 °C=72°F=295 K
    • Boiling point of water
      • 100 °C=212°F=373 K