Transcript 101Lec1

Chapter 1: Measurements
Order of Operations
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Start with calculations inside ( )
Exponents and Logs are calculated next
Multiplication and Division follow
Addition and subtraction are last
1.1: Units of Measurement
Property
Metric Unit US Unit
Conversion
Length
Meter (m)
Inch (in)
1m = 39.4 in
1in = 2.54 cm
Volume
Liter (L)
Quart (qt)
1L = 1.06 qt
1qt = 946 mL
Mass
Kilograms
(kg)
Pound (lb)
1kg = 2.20 lb
1lb = 454 g
Temp
Deg Celsius
Deg
Fahrenheit
1.2: Scientific Notation
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Large Numbers: 12,000,000 = 1.2 x 107
Small Numbers: 0.00000012 = 1.2 x 10-7
Short hand: Mass of a proton = 1.67 x 10-27 kg
Easier to determine magnitude:
0.00000000000000000000000000167 kg
• A lake has 1,320,000,000 liters of water.
What is its volume in scientific notation?
1.3: Measured and Exact
Numbers
Measured Numbers:
• Uncertainty and error
in measurement
• Mass of an apple is
measured to be
roughly 486g
Exact Numbers:
• From definition or
counting items
• The number of apples
in a sack is exactly 6
• There are exactly 12
inches in a foot
1.4: Significant Figures
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All measured values have error
Accurate measurements are close to actual value
Precise measurements are repeatable
Significant figures are used to track digits of
importance through calculations
• Good explanation of sig figs is given on page 10
Sig Figs Continued
• Only used for measured numbers not exact
• All non-zero digits are significant
• Zeroes may or may not be significant (significant if at
end of a decimal number or between non-zero digits)
• 21.0 has 3 sig figs and 1560. has 4 sig figs
• 0.007 has 1 sig fig but 0.0070 has 2 sig figs
• 400 has 1 sig fig unless it’s actually 4.00 x 102 which
has 3 sig figs (sci. not. tracks sig figs)
• 2012 has 4 sig figs
1.5: Sig Figs in Calculations
• Rounding off:
– If first digit dropped is 4 or less the number is rounded
down. If it is 5 or more the number is rounded up
• Multiplication and Division:
– The number with the lesser amount of sig figs
determines the sig figs in the answer
• Addition and Subtraction:
– The number with the lesser amount of decimal places is
used to determine decimal places in the answer
Examples of Sig Figs in
Calculations
• The number 19.4 is rounded to 19 but the
number 19.5 is rounded to 20
• 10.5 x 11.75 = 123.375  123
• 150 / 2 = 75  80
• 112 + 0.15 = 112.15  112
• 75.585 – 1.42 = 74.165  74.17
• Be careful, the calculator may not display
correct number of Sig Figs!
1.6 Metric and SI System
Prefixes
Prefix
Abbreviation Conversion
Mega
M
1,000,000
Kilo
k
1,000
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1
Centi
c
1/100
Milli
m
1/1,000
Micro
μ
1/1,000,000
Volume and Converting Cubic Units
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1000 mL = 1 L
1 mL = 1 cm3 = 1 cc
100 cm = 1 m
100 cm3 IS NOT = 1 m3
(1m)3 = (100 cm)3 = 1,000,000 cm3
1.7: Conversion Factors
• Used for converting units and used A LOT in chemistry!
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Step 1 – Identify information given
Step 2 – Plan how to reach desired units
Step 3 – Select necessary conversion factors
Step 4 – Set up conversions so they cancel
Step 5 – Solve problem and determine sig figs*
Unit should cancel leaving you with desired units
1.8: Density
Mass
Density 
Volume
• The relationship between
mass and volume
• Density can be used as a
conversion factor
• Specific gravity is
unitless but roughly equal
to density numerically
DensityMat erial
SpecificGravity 
DensityWat er
1.9: Temperature
 F  1.8(C )  32
( F  32)
C 
1.8
K  C  273
C  K  273
• Measures how hot or cold
things are
• Measure in Fahrenheit,
Celcius and Kelvin scales
• Can NOT be converted
simply using conversion
factors
• Different 0° temps for
each scales