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# 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)
• 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