International System of Units 3'2

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International System of Units 3.2
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The International System of Units
3.2

• 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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Measuring with SI Units
3.2

• Measuring with SI Units
• Which five SI base units do chemists commonly use?

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Measuring with SI Units
3.2

• All measurements depend on units that serve as
  reference standards. The standards of measurement
  used in science are those of the metric system.
• The International System of Units (abbreviated
  SI, after the French name, Le Système
  International dUnités) is a revised version of
  the metric system.

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Measuring with SI Units
3.2

• The five SI base units commonly used by chemists
  are the meter, the kilogram, the kelvin, the
  second, and the mole.

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Units and Quantities
3.2

• Units and Quantities
• What metric units are commonly used to measure
  length, volume, mass, temperature and energy?

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Units and Quantities
3.2

• 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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Units and Quantities
3.2

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

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Units and Quantities
3.2

• 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 ? 10
  cm ? 10 cm 1000 cm3 1 L).

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Units and Quantities
3.2

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

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Units and Quantities
3.2

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

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Units and Quantities
3.2

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

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Units and Quantities
3.2

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

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Units and Quantities
3.2

• 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 4C is 1 g.

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Units and Quantities
3.2

• Common metric units of mass include kilogram,
  gram, milligram, and microgram.

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Units and Quantities
3.2

• Weight is a force that measures the pull on a
  given mass by gravity.
• The astronaut shown on the surface of the moon
  weighs one sixth of what he weighs on Earth.

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Units and Quantities
3.2

• Units of Temperature
• Temperature is a measure of how hot or cold an
  object is.
• Thermometers are used to measure temperature.

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Units and Quantities
3.2

• Scientists commonly use two equivalent units of
  temperature, the degree Celsius and the kelvin.

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Units and Quantities
3.2

• On the Celsius scale, the freezing point of
  water is 0C and the boiling point is 100C.
• 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 equal to ?273.15 C.

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Units and Quantities
3.2

• 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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Units and Quantities
3.2

• Conversions Between the Celsius and Kelvin Scales

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3.4
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3.4
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3.4
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3.4
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for Sample Problem 3.4
Problem Solving 3.17 Solve Problem 17 with the
help of an interactive guided tutorial.
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Units and Quantities
3.2

• 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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Units and Quantities
3.2

• 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
  1C.

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Units and Quantities
3.2

• 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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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?
• meter
• gram
• second
• 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
• both the mass and the weight do not change.
• both the mass and the weight change.
• the mass remains the same, but the weight
  changes.
• 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
• 303 K.
• 300 K.
• 243 K.
• 247 K.

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END OF SHOW