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Measurement and UnitsMeasurement and Units

• Seven Fundamental SI Units of Measurement.

Physical Quantity Name of Unit Abbreviation Mass kilogram kg

Length meter m Temperature kelvin K

Amount of substance mole mol Time second s

Electric current ampere A Luminous intensity candela cd

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Measurement and UnitsMeasurement and Units

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• Some Prefixes for Multiples of SI Units.Factor Prefix Symbol

1,000,000,000 = 109 giga G1,000,000 = 106 mega M

1,000 = 103 kilo k100 = 102 hecto h10 = 101 deka da0.1 = 10-1 deci d

0.01 = 10-2 centi c0.001 = 10-3 milli m

0.000,001 = 10-6 micro µ0.000,000,001 = 10-9 nano n

0.000,000,000,001 = 10-12 pico p

Measurement and UnitsMeasurement and Units

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Measurement and UnitsMeasurement and Units

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• Some Derived Quantities.

Quantity Definition Derived Unit (Name)

Area Length times length m2

Volume Area times length m3

Density Mass per unit volume kg/m3

Speed Distance per unit time m/s

Acceleration Change in speed per unit time m/s2

Force Mass times acceleration (kg·m)/s2 (newton, N)

Pressure Force per unit area kg/(m·s2) (pascal, Pa)

Energy Force times distance (kg·m2)/s2 (joule, J)

Measurement and UnitsMeasurement and Units

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• Density relates the mass of an object to its volume.

• Density decreases as a substance is heated

because the substance’s volume increases.

• Knowing the density of a substance allows

measurements in volume to be recorded in mass.

Measurement and UnitsMeasurement and Units

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Measurement and UnitsMeasurement and Units

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• Densities of Some Common Materials.

Substance Density (g/cm3) Substance Density (g/cm3)

Ice (0.0°C) 0.917 Human Fat 0.94

Water (4.0°C) 1.0000 Cork 0.22–0.26

Gold 19.31 Table Sugar 1.59

Helium (25.0°C) 0.000164 Balsa Wood 0.12

Air (25.0°C) 0.001185 Earth 5.54

Measurement and UnitsMeasurement and Units

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• What is the density of glass (in grams per cubic

centimeter) if a sample weighing 26.43 g has a

volume of 12.40 cm3?

• Chloroform, a substance once used as an

anesthetic, has a density of 1.483 g/mL at 20°C.

How many mL would you use if you needed 9.37 g?

Measurement and UnitsMeasurement and Units

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Measurement and UnitsMeasurement and Units

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• Temperature Conversions:

• The Kelvin and Celsius

degree are essentially

the same because both

are one hundredth of the

interval between freezing

and boiling points of water.

Measurement and UnitsMeasurement and Units

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Measurement and UnitsMeasurement and Units

• Temperature Conversions:

• Celsius (°C) — Kelvin

temperature conversion:

Kelvin (K)

= °C + 273.15

• Fahrenheit (°F) — Celsius

temperature conversions: 32

5

9 )32(

9

5

CFFC

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• Carry out the indicated temperature conversions:

(a) –78°C = ? K

(b) 158°C = ? °F

(c) 375 K = ? °C

(d) 98.6°F = ? °C

(e) 98.6°F = ? K

Measurement and UnitsMeasurement and Units

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English System of UnitsEnglish System of Units

Volume:Gallon (gal) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl oz)

Length:Mile (mi) = 1760 yards (yd) = 5280 feet (ft) = 63360 inches (in)

Mass:1 ton = 2000 pounds (lb) = 32000 ounces (oz)

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• Dimensional-Analysis method uses a conversion factor to express the relationship between units.

Original QuantityConversionFactor = Equivalent Quantity

Example: Express 2.50 kg in lb.

ConversionFactor: 1.00 kg = 2.205 lb arranged as 2.205 lb1.00 kg

2.50 kg 2.205 lb1.00 kg

= 6.00 lb (correct to 3 significant figures)

Measurement and UnitsMeasurement and Units

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Common Conversion FactorsCommon Conversion Factors

2.54 cm = 1 in

454 g = 1 lb

0.946 L = 1 qt

1 mL = 1 cm3 = 1 g water

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Ball Park Conversion Factors

Ball Park Conversion Factors

1 m ~ 1 yd

1 L ~ 1 qt

1 kg ~ 2 lb

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Conversion FactorsConversion Factors

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Conversion FactorsConversion Factors

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• The volcanic explosion that destroyed Krakatau on

August 17, 1883, released an estimated 4.3 cubic

miles (mi3) of debris into the atmosphere. In SI

units, how many cubic meters (m3) were released?

Conversion FactorsConversion Factors

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• How many meters are there in a marathon race

(26 miles and 385 yd)?

• How large, in cubic centimeters, is the volume of a

red blood cell if the cell has a circular shape with a

diameter of 6.0 x 10–6 m and a height of 2.0 x 10–6 m?

Conversion FactorsConversion Factors

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Interesting Conversion Problem

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Interesting Conversion Problem

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Interesting Conversion Problem

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Interesting Conversion ProblemInteresting Conversion Problem

• A test rat weighs 512 g

• The rat begins to eat Bayer Aspirin tablets 1 at a time.

• How many tablets (on average) will have been consumed when the rat dies?