Measurement In Chemistry

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MeasurementInChemistry
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MeasurementAt the conclusion of our time
together, you should be able to

1. Explain the difference between the two types of
   observations
2. Give examples of 5 basic SI measuring units
3. Give examples of 3 different derived units from
   the basic SI units
4. Vary the amounts of the SI measuring units with
   10 different prefixes and define each
5. Explain the difference between mass and weight
6. List and explain 5 different units for volume.

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Types of Observations and Measurements

• We make QUALITATIVE observations of reactions
  changes in color and physical state.
• We also make QUANTITATIVE observations that
  involve MEASUREMENTS with numbers and units.

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Some Tools for Measurement

Which tool(s) would you use to measure A.
temperature B. volume C. time D. weight
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Stating a Quantitative Measurement

• In every measurement there is a
• Number (Quantity) followed by a
• Unit from a measuring device

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Quantitative Measurements in Chemistry Must
Include Units!
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Standards of Quantitative Measurement

• When we measure, we use a measuring tool to
  compare some dimension of an object to a
  standard.

For example, at one time the standard for length
was the kings foot. What are some problems with
this standard?
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SI Measurement

• Le Système International dUnités
• Adopted in 1960 by the General Conference on
  Weights and Measures.
• International Standards are kept in France.
• Among countries with non-metric usage, the U.S.
  is the only country significantly holding out.
  The U.S. officially adopted SI in 1866.
• Liberia and Myanmar are changing over.

Liberia
Information from U.S. Metric Association
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Base SI Units
Quantity Unit Symbol
Length meter m
Mass kilogram kg
Temperature kelvin K
Time second s
Amount of Substance mole mol
Luminous Intensity candela cd
Electric Current ampere a
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Units Of Measurement You Must Know

• Use SI units based on the metric system
• Length
• Mass
• Volume
• Time
• Temperature

meter, m
kilogram, kg
liter, L
seconds, s
kelvin, K
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Unit for Length

• 1 Meter
• Note Not Foot!!

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Metric Prefixes

• Kilo- means 1000 of that unit
• 1 kilometer (km) 1000 meters (m)
• Centi- means 1/100 of that unit
• 1 meter (m) 100 centimeters (cm)
• 1 dollar 100 cents
• Milli- means 1/1000 of that unit
• 1 meter (m) 1000 millimeters (mm)

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Metric Prefixes
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Metric Prefixes
You Will Need to Know Grand Master King Henry
Died by Drinking Chocolate Milk Monday Night
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Metric Prefixes You Need to Know
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103 meters 1 km
1 kilometer (km)
1 meter (m)
1 dm (decimeter)
10 dm 1 m
1 cm (centimeter)
100 cm 1 m
1 mm (millimeter)
103 mm 1 m
1 ?m (micrometer)
106 ?m 1 m
1 nm (nanometer)
109 nm 1 m
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Unit for Mass

• 1 Kilogram
• Note Not Gram!!

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Unit for Weight

• 1 Newton
• 1 N kg m/s2

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A Weighty Problem
On 9/23/99, 125,000,000 Mars Climate Orbiter
entered Mars atmosphere 100 km lower than
planned and was destroyed by heat.
1 lb 1 N
1 lb 4.45 N
This is going to be the cautionary tale that
will be embedded into introduction to the metric
system in elementary school, high school, and
college science courses till the end of time.
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Mass and Weight
Weight is force of the gravitational pull on an
object. It would be different on the moon than
it is on earth.
Mass is a measure of the amount of matter in an
object.
Mass and weight are directly related as long as
we remain on earth at the same elevation. That
is, if one object has twice the mass of another,
then its weight on earth would also be twice as
large.
However, if we take the same object to Denver,
Colorado, the mass stays the same but the weight
would be different. Why??
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Mass vs. Weight

• Mass Amount of Matter
• (grams, measured with a BALANCE)
• Weight Force exerted by the mass, only present
  with gravity
• (pounds, measured with a Scale)

Can you hear me now?
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Unit for Volume

• 1 Meter Cubed
• Note A Derived Unit!!
• To Big, So Generally Use the Liter

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• What is a Liter??

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Length and Volume
1 m 10 dm
therefore 1 m3 103 dm3
therefore 1 dm3 103 cm3
1 dm 10 cm
1 L 1 dm3 and 1 L 103 mL
so
1 L 1 dm3 103 mL 103 cm3 103 cc
so
This means that 1 milliliter (mL) is the same as
1 cubic centimeter (cc). These terms are
often used interchangeably.
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Units for Volume

• m3
• cm3
• dm3
• L Liter
• mL

• 1 dm3 1 L
• 1 cm3 1 mL

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Other Derived SI Units
Quantity Unit Symbol
Volume cubic meter m3
Density kilograms per cubic meter kg/m3
Speed meter per second m/s
Newton kg m/ s2 N
Energy Joule (kg m2/s2) J
Pressure Pascal (kg/ms2) Pa
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Units for Energy

• Joule J
• calorie 1 cal 4.184 J
• 1 cal quantity of heat needed to raise the
  temperature of 1 g of water by 1 oC.

1 kcal 1000 cal
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MeasurementLets see if you can

1. Explain the difference between the two types of
   observations
2. Give examples of 5 basic SI measuring units
3. Give examples of 3 different derived units from
   the basic SI units
4. Vary the amounts of the SI measuring units with
   10 different prefixes and define each
5. Explain the difference between mass and weight
6. List and explain 5 different units for volume.

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Learning Check

• Match L) length M) mass V) volume
  
• ____ A. A bag of tomatoes is 4.6 kg.
• ____ B. A person is 2.0 m tall.
• ____ C. A medication contains 0.50 g Aspirin.
• ____ D. A bottle contains 1.5 L of water.

M
L
M
V
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Learning Check

• What are some U.S. units that are used to
  measure each of the following?
• A. length
• B. volume
• C. weight
• D. temperature

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Which Metric Prefix is Generally Used?
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Learning Check

• 1. 1000 m 1 ___ a) mm b) km c) dm
• 2. 0.001 g 1 ___ a) mg b) kg c)
  dg
• 3. 0.1 L 1 ___ a) mL b) cL c)
  dL
• 4. 0.01 m 1 ___ a) mm b) cm c)
  dm

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Learning Check

• Select the unit you would use to measure
• 1. Your height
• a) millimeters b) meters c) kilometers
• 2. Your mass
• a) milligrams b) grams c) kilograms
• 3. The distance between two cities
• a) millimeters b) meters c) kilometers
• 4. The width of an artery
• a) millimeters b) meters c) kilometers