Chapter 2 Standards of Measurement

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You can do it.
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Chapter 1Matter and Measurement
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States of Matter
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Solid

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Liquid

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Gas

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Plasma

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Matter
Pure substances (homogeneous composition)
Mixtures of two or more substances
Elements
Compounds
Solutions (homogeneous composition one phase)
Heterogeneous mixtures (two or more
phases)
Figure 3.2 (page 48)
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Classifying Substances
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Mixtures

• Homogeneous
• Heterogeneous

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Pure substance

• A particular kind of matter with a definite,
  fixed composition
• Elements
• Compounds

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Compounds

• Two or more elements
• New
• Definite
• Can be

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How would you classify?

• Gatorade
• Caesar salad
• Water
• Coffee
• An iron nail
• Air
• Milk

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Methods of Separation

• Do not cause chemical changes

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Filtration

• Used for
• Gravity
• Vacuum

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Sublimation

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Evaporation

• Solutions

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Distillation

• Relies on

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Chromatography

• Relies on

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Decantation

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Crystallization

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The Metric SystemThe International System of
Units

• Standards of measurement
• Base units (7) see Table 1.4 pg 14
• MASS
• LENGTH
• TIME
• COUNT, QUANTITY
• TEMPERATURE
• ELECTRIC CURRENT
• LUMINOUS INSTENSITY

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The Metric System

• Derived Units
• AREA
• VOLUME
• ENERGY
• FORCE
• PRESSURE
• POWER
• VOLTAGE
• FREQUENCY
• ELECTRIC CHARGE

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Density

• Common ratio used in chemistry
• Physical property of a substance
• D
• SI units kg/m3

• Solid
• g/cm3
• Liquid
• g/mL
• Gas
• g/L

Can change due to temperature and/or pressure
changes
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Density

• Find the density of a piece of metal with a
  volume of 2.7 cm3 and a mass of 10.8 g.

2. Determine the mass of an object with a density
of 0.24 g/cm3 and a volume of 2 cm3.
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The Metric System

• Metric Prefixes make base unit larger or
  smaller
• Table 1.5 pg 14
• Based on 10
• Math method vs. Stairs

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Conversion Practice

• Convert a volume of 12 microliters into
  centiliters
• Express a distance of 15 meters in kilometers
• Convert 83 cm into meters
• Which is the longer amount of time, 1351 ps or
  1.2 ns?
• Convert 16 dL into L

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Uncertainty in Measurement

• Why are digits in measurements uncertain?
• Instruments never completely free of flaws
• Always involves estimation
• Choose the right instrument for the job
• May be estimated for you (electronic scales)
• Scale is marked but you estimate the in-between

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Uncertainty in Measurement

• Precision getting the same result again and
  again under same conditions
• Accuracy close to accepted value

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Significant Digits

• All digits known with certainty plus one final
  digit which is uncertain (or estimated)
• All non-zeros
• A zero is significant when
• It is
• It is
• A zero is not significant when
• It is
• It is

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Significant Digits - PRACTICE

• How many significant digits?
• 54.23
• 23.00005
• 0.0004
• 35000
• 0.000504
• 45.623200
• 5,000,000
• 4,000,000.1

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Significant Digits - Calculations

• Addition and Subtraction
• Round answer to have final digit in the SAME
  PLACE as the last digit in the LEAST ACCURATE
  MEASUREMENT
• 1.21 5.002 10.
• 34.5 12.45 23.0505
• 186.31 11.1
• 12.0231 3.86
• 0.100012 120.
• 1200 12 15 0.5

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Significant Digits - Calculations

• Multiplication and Division
• The answer has as many sig figs as the number
  with the fewest sig figs
• 14.8 x 3.1
• 18.2 x 3.0
• 52/1.5
• 321.868783 x 1
• 2400 x 2.123
• 15000/12.354

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Scientific Notation

• Convenient way of writing very large or very
  small numbers and showing only significant
  figures
• Number between 1 10 with a power of ten
• 5120 becomes 5.12 x 103
• Move decimal point in original number to make
  number 1-10
• Move left move right -

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Scientific Notation Practice

• 123,000
• 0.000045
• 23.45
• 0.0000000003
• 1,000,000

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Scientific Notation

• Math with
• Use the EE or EXP button on your calculator.
• For example
• (1.25 x 105) (5.25 x 102)
• Keystrokes are
• Or

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Types of Measurements

• Mass
• Expressed in
• Does
• Weight
• Expressed in same units

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Types of Measurements

• Volume
• Cubic
• Many instruments to measure
• Temperature
• Kelvin
• Degrees Celsius
• Degress Farenheit

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Conversion Factors

• Enable movement between metric system and
  English system
• See back cover of book and Appendix III
• Common conversions you should memorize
• 1 inch 2.54 cm
• 1 mile 1.609 km
• 1 kg 2.20 pounds
• 1 mL 1 cm3
• 0 K -273.15 0C
• 0F 1.8(0C) 32

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Dimensional Analysis(Problem Solving)

• Remember ALWAYS use UNITS OF MEASUREMENT in
  your work!!!
• A technique of converting between units
• Same system (metrics)
• Different systems (inches to meters)
• Chemical equations.later chapters

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Dimensional Analysis(Problem Solving)

• Conversion Factors ratio derived from the
  equality between 2 different units
• 3 feet 1 1 dollar 1
• 1 yard 4 quarters
• CF can be written either way
• 1 minute 1 60 seconds 1
• 60 seconds 1 minute

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Dimensional Analysis(Problem Solving)

• The t method

unit given unit wanted unit wanted
unit given
Conversion Factor
Example How many liters are in 125.6 gallons?
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Dimensional Analysis(Problem Solving)
Dimensional Analysis(Problem Solving)
How many seconds are in 4.15 hours?
If a student needs 1.5 mL of water, how many cups
does he need?