© copyright pearson prentice hall slide 1 of 33 © 2009, prentice- hall, inc. units of measurement

© Copyright Pearson Prentice Hall

Slide 1 of 33

© 2009, Prentice-Hall, Inc.

Units of Measurement


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3.2 The International System of Units

In the signs shown here, the distances are listed as numbers with no units attached. Without the units, it is impossible to communicate the measurement to others. When you make a measurement, you must assign the correct units to the numerical value.


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SI Units

•Système International d’Unités

•A different base unit is used for each quantity.


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Metric System

Prefixes convert the base units into units that are appropriate for the item being measured.

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The International System of Units

>3.2 Units and Quantities

Units of Length

In SI, the basic unit of length, or linear measure, is the meter (m). For very large or and very small lengths, it may be more convenient to use a unit of length that has a prefix.

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Common metric units of length include the centimeter, meter, and kilometer.

Size and Scale of Common Things

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Units of Volume

The SI unit of volume is the amount of space occupied by a cube that is 1 m along each edge. This volume is the cubic meter (m)3. A more convenient unit of volume for everyday use is the liter, a non-SI unit.

A liter (L) is the volume of a cube that is 10 centimeters (10 cm) along each edge (10 cm x 10 cm x 10 cm = 1000 cm3 = 1 L).

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Volume

• The most commonly used metric units for volume are the liter (L) and the milliliter (mL).

–A liter is a cube 1 dm long on each side.

–A milliliter is a cube 1 cm long on each side.

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Common metric units of volume include the liter, milliliter, cubic centimeter, and microliter.

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The volume of 20 drops of liquid from a medicine dropper is approximately 1 mL.

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A sugar cube has a volume of 1 cm3. 1 mL is the same as 1 cm3.

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A gallon of milk has about twice the volume of a 2-L bottle of soda.

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Units of Mass

The mass of an object is measured in comparison to a standard mass of 1 kilogram (kg), which is the basic SI unit of mass.

A gram (g) is 1/1000 of a kilogram; the mass of 1 cm3 of water at 4°C is 1 g.

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Common metric units of mass include kilogram, gram, milligram, and

microgram.

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> SI Prefixes

Prefix Symbol Multiply the root word by Power of 10

tera - T 1 000 000 000 000 1012

giga - G 1 000 000 000 109

mega - M 1 000 000 106

kilo - k 1 000 103

hecto - h 100 102

deca - da 10 101

Root Unit 1 100

deci - d 0.1 10-1

centi - c 0.01 10-2

milli - m 0.001 10-3

micro - m 0.000 001 10-6

nano - n 0.000 000 001 10-9

pico - p 0.000 000 000 001 10-12

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> Basic Metric prefixes

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Convert the following.

1. 200 m = __________ km 6. 2000 cL = __________ L

2. 1.2 L = __________ L 7. 0 .125 pm = __________ cm

3. 6000 cm = __________ m 8. 12 000 mg = __________ g

4. 2500 g = __________ Mg 9. 5 km = __________Tm

5. 500 hm = __________ m 10. 2 km = __________ mm

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Units of Temperature

Temperature is a measure of how hot or cold an object is. It is a measure of the average kinetic energy of the particles in a substance.

Thermometers are used to measure temperature.

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Temperature

By definition temperature is a measure of the average kinetic energy of the particles in a sample.

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Temperature• In scientific

measurements, the Celsius and Kelvin scales are most often used.

• The Celsius scale is based on the properties of water.

–0°C is the freezing point of water.

–100°C is the boiling point of water.

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Temperature

• The Kelvin is the SI unit of temperature.

• It is based on the properties of gases.

• There are no negative Kelvin temperatures.

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On the Celsius scale, the freezing point of water is 0°C and the boiling point is 100°C.

On the Kelvin scale, the freezing point of water is 273.15 kelvins (K), and the boiling point is 373.15 K.

The zero point on the Kelvin scale, 0 K, or absolute zero, is the temperature at which all molecular motion would stop. It is equal to -273.15 °C.

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Because one degree on the Celsius scale is equivalent to one kelvin on the Kelvin scale, converting from one temperature to another is easy. You simply add or subtract 273, as shown in the following equations.

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Conversions Between the Celsius and Kelvin Scales

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Temperature• The Fahrenheit

scale is not used in scientific measurements.

• °F = 9/5(°C) + 32

• °C = 5/9(°F − 32)


SAMPLE PROBLEM

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3.4


SAMPLE PROBLEM

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3.4


SAMPLE PROBLEM

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3.4


SAMPLE PROBLEM

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3.4


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Practice Problems

Problem Solving 3.17 Solve Problem 17 with the help of an interactive guided tutorial.

for Sample Problem 3.4


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Practice Problems Celsius to Fahrenheit

°C = (°F – 32) • 5/9

°F = 9/5 • °C + 32

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Units of Energy

Energy is the capacity to do work or to produce heat.

The joule and the calorie are common units of energy.

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The joule (J) is the SI unit of energy.

One calorie (cal) is the quantity of heat that raises the temperature of 1 g of pure water by 1°C.

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This house is equipped with solar panels. The solar panels convert the radiant energy from the sun into electrical energy that can be used to heat water and power appliances.


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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

3.2 Section Quiz.

3.2.


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3.2 Section Quiz.

1. Which of the following is not a base SI unit?

a. meter

b. gram

c. second

d. mole


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3.2 Section Quiz.

2. If you measured both the mass and weight of an object on Earth and on the moon, you would find that

a. both the mass and the weight do not change.

b. both the mass and the weight change.

c. the mass remains the same, but the weight changes.

d. the mass changes, but the weight remains the same.


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3.2 Section Quiz.

3. A temperature of 30 degrees Celsius is equivalent to

a. 303 K.

b. 300 K.

c. 243 K.

d. 247 K.

END OF SHOW

© copyright pearson prentice hall slide 1 of 33 © 2009, prentice- hall, inc. units of measurement

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