CHEMISTRY IS LARGELY A QUANTITATIVE SCIENCE

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CHEMISTRY IS LARGELY A QUANTITATIVE SCIENCE

• Theories and ideas are tested by measurement
• Measurements are usually quantitative have
  numbers
• Science is built on a foundation of mathematics.
• In recording measurements, it is necessary to
  understand
• SIGNIFICANCE of numbers
• importance of UNITS.

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Learning Objectives about Units

• Understand importance of units in measurement
• Identify common metric units
• Apply common metric prefixes
• Use simple unit conversions
• Recognize the scales of temperature
• Perform conversions between temperature scales

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Systems of measurements

• English System - what the United States uses
  today derived from the 'Kings" feet (Old
  England). Also known as the United States
  Customary System (USCS)
• Units
• 1 foot (big feet")
• 1 inch (knuckle)
• 1 yard (King Henry I - nose to thumb)

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System Internationale (S.I.) the new

• The creation of the decimal Metric System at the
  time of the French Revolution and the creation of
  two platinum standards representing the meter and
  the kilogram was the first step in the
  development of the present International System
  of Units.
• Science has adopted the S.I. When we say
  metric we mean S.I.

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Know ones units

• Not only inexperienced chemistry students can be
  confused by units
• Whoops!

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Prefixes
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Remember these case is important compare M and
m

• mega- (M) 1,000,000 106
• kilo- (k) 1,000 103
• deci- (d) 1/10 10-1
• centi- (c) 1/100 10-2
• milli- (m) 1/1,000 10-3
• micro- (?) 1/1,000,000 10-6
• nano- (n) 1/1,000,000,000 10-9

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The seven fundamental units of measurement
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Length meter (m)

• Length is a fundamental unit. In the metric
  system, the meter is a the standard unit for
  measuring length. It is a little longer than a
  yard.
• The standard unit of metric length is kept in
  Paris. It is equal to 39.37 inches. Since the
  meter is equal to 100 centimeters (cm), then 1
  inch is equal to 2.54 cm.
• Comparisons
• centimeter - width of your fingernail
• kilometer - 0.60 miles
• millimeter - thickness of a dime

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Mass kilogram (kg)

• Mass is a fundamental unit it is a measure of
  the quantity of matter present. Although we
  typically use the words mass and weight
  interchangeably in normal conversation, mass and
  weight actually have different meanings. Weight
  includes the effect of gravity on mass. In a
  space capsule, your weight would be zero (absence
  of gravity) but your mass would be the same value
  as it was on earth. The standard unit of mass is
  the kilogram (kg).
• Conversions factors
• 1 pound 454 g
• 2.2 pounds (lb) 1 kilogram (kg)
• 1 gram (g) 1000 milligrams (mg) or 1 mg 0.001
  g
• 1 kilogram (kg) 1000 grams (g) or 1 g 0.001
  kg

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Volume

• volume is a derived unit (using length units).
  It is a measure of space. In simple terms, it is
  a measure of three (3) length units in three
  dimensions (breadth, length and width). The
  standard unit of measurement is the meter cubed
  (m3) or the centimeter cubed (cm3).
• In chemistry, volume is typically measured for a
  liquid. The standard unit of measurement for a
  liquid is the liter (L). The liter is similar to
  a quart in the English system.
• Conversion factors
• 1 liter (L) 1.06 quarts (qt)
• 1 quart (qt) 0.946 liters (L)
• 1 liter (L) 1000 milliliters (ml) or
• 1 milliliter (ml) 0.001 liter (L)
• 1 milliliter (ml) 20 drops
• At room temperature, 1 milliliter (ml) of water
  1 cm3. (or 1 CC)

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Temperature

• A fundamental unit. There are three(3)
  temperature scales
• 
  BPH20 FPH2O
  Difference
• (1) Fahrenheit (F) 212
  32 180
• (2) Celsius (centigrade) (C) 100
  0 100
• (3) Kelvin (K)
  373 273 100
• Conversion
• Kelvin to Celsius (K -gt C) C K - 273
• Celsius to Kelvin (C -gt K) K C 273
• Celsius to Fahrenheit (C -gt F)
• i multiply C x 9/5
• ii Add C x 9/5 32
• Fahrenheit to Celsius (F -gt C)
• i add F - 32
• ii multiply (F - 32) x 5/9

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Derived units

• Derived units can be resolved into combinations
  of fundamental units
• Area and volume involve only the units of length
• Most involve combinations of different units

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Dimensions

• It is important to keep track of the dimensions
  in derived units.
• All the more when making conversions
• 1 cm 10 mm
• 1 cm2 100 mm2
• 1 cm3 1,000 mm3

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Conversion factors

• Making conversions between different units is
  very important
• Always keep track of the units
• Make use of unit factors
• There are 1000 mg in 1 g (conversion factor)
• 1000 mg/1 g 1 1 g/1000 mg 1 (unit factors)
• There are two unit factors for any conversion

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Unit factors at work

• How many grams are there in 2680 mg of sucrose?
• We know there are 1 000 mg in 1 g
• 1 g/1000 mg 1 (unit factor)
• ? g amount in mg x unit factor
• ? g 2680 mg x 1 g/1000 mg 2.680 g
• Unit factor has value of 1 no change in value
• Application of unit factor causes old units to
  cancel
• Never forget to show units of any measurement
  unless it is a unit-less quantity

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Handy conversions
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Density

• Mass divided by volume
• Units are
• g/cm3(solid)
• g/mL (liquid)
• g/m3 (gas)

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Density and temperature

• In most cases, the density of a substance
  decreases with temperature. (Why is that?)
• Water provides a critical exception to the rule