Biochemistry

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Physical Chemistry
Environmental Chemistry
CHEMISTRY
Nanotechnology
Organic Chemistry
Chemical Engineering
Biochemistry
Inorganic Chemistry
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Measurement

• Metric system (National Assembly of France, 1790)
• International System of Units (SI, 1960)

Derived units combinations of fundamental
units Ex. Speed (m/s)
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Equipment for Measurement





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Scientific Notation
Width of a human hair 0.000008 m
Coefficient
Power of Ten 10x
Coefficient?
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Power?
10-6
8 x 10-6 m
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Scientific Notation

• How many atoms of water are in a Lake Washington?
• 97,000,000,000,000,000,000,000,
  000,000,000,000,000 atoms
• -or-
• 9.7 x 1037 atoms

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Scientific Notation on Calculators

• Your calculator should work with scientific
  notation! Look for

EE
EXP
Note 9.64 x 105 9.65 E5
Coefficient
Power of Ten
2. x 10-8 2.E-8
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Scientific Notation

• Conversion to a standard number
• 3.252 x 106

If power of ten is positive, move decimal point
to the RIGHT (add zeros if necessary)
3252000
If power of ten is negative, move decimal point
to the LEFT (add zeros if necessary)
4.56 x 10-3
0.00456
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Measured Numbers

• Numbers obtained when you measure a quantity
• Estimate the final digit

4.8 in
Read greater than 4 and less than 5 estimate
last digit
4.84 in
Read greater than 4.8 and less than 4.9 estimate
last digit
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Significant Figures

• All measured digits, including the estimated
  digit
• 4.84 cm
• 2045 g
• 2.333 x 10-5 L
• 50. s
• Zeros not significant in 2 situations
• At the beginning of a decimal number
• At the end of a number without decimal point
• 4500 cm
• 0.0063 kg
• 0.05202 L

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Exact Numbers

• A counted number (not measured!)
• Ex. of students in this classroom
• A definition comparing two units in same
  measurement system
• Ex. 1 ft 12 in
• Ex. 1 kg 1000 g
• NOT considered as significant figures!

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Significant Figures in Calculations

• In lab, at work, we measure things. Then what?
• The number of sig figs in measured numbers limits
  the number of sig figs in a calculated answer.
• You cant have more detail in your answer than
• you have in your measurements
• Number of sig figs in answer depends on what
  type of calculations you performed

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Sig Figs in Calculations

• Multiplication and Division
• Final answer has the same number of sig figs as
  the measurement with the fewest significant
  figures
• Addition and Subtraction
• Final answer has the same number of decimal
  places as the measurement with the fewest decimal
  places

24.64 x 3.2 78.848
79.
3.525 - 5.2 -1.675
-1.7
3.525 6.475 10
10.000
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Rounding Rules

• How do we limit the number of sig figs? Rounding!
  
• Look at first non-significant number (to be
  dropped)
• Is this number 4 or less?
• Is this number 5 or more?

Round down
Round up
2390.321 to 4 sig figs
2390.
0.0056194 to 2 sig fig
0.0056
688511 to 3 sig figs
689000
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Prefixes

• Is it easier to write
• 590000 g or 590 kg?
• 0.0004 g or 0.4 mg?
• Prefixes can be attached to units to increase or
  decrease size by a factor of 10
• (multiply by 10 or divide by 10)

Multiply by 10x
Multiply by 10-x
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Common Prefixes with SI Units
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Equalities used in Measurements

• Equality
• A relationship between two units that measure
  the same quantity
• Length
• 1 m 100 cm 1000 mm
• Volume
• 1 L 10 dL 1000 mL
• 1 dL 100 mL

Cubic centimeter cc
1 cm x 1 cm x 1 cm 1 cm3
1 cc 1 cm3 1 mL
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Volume Conversions

• If 1 cubic centimeter equals 1 mL,
• how many milliliters does 1 cubic meter equal?

1 m 100 cm
100 cm x 100 cm x 100 cm 1000000 cm3
1000000 cm3 1000000 mL
1 x 106 mL
1 m3 1000 L
1 x 103 L
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Conversion Factors Changing Between Units

• 1 hr 60 min

Conversion Factor
Metric Conversion Factor
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More Conversion Factors
Metric Conversion Factors
Metric- U.S. System Conversion Factors
1 kg 2.20 lb
1 km 0.621 mi
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More Conversion Factors

• Standard equalities can be looked up in a table
  (Table 1.9 in your book, for example)
• Other equalities may be stated in a problem

• Examples
• The average speed of cars driving on I-5 during
  rush hour is 11 mph.

Equality 11 miles 1 hour

• One five pound bag of sugar costs 4.00.

Equality 1 bag 5 lb 4.00
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Percents as Conversion Factors

• Percent means 1 per 100

• Example
• If a person is 20 body fat by mass, then

20 kg fat 100 kg body total
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End of class Practice Questions

• How many sig figs are in each the following?
• 0.00500 L
• 53,069 s
• 0.00004715 m
• 0.509 kg
• Write the numbers above in scientific notation.
• How many sig figs does each have now?
• Write a conversion factor relating micrograms to
  grams

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Practice Questions
What is the temperature on each (C) thermometer
shown? (sig figs!)
4.9 C
61.5 C

• Is each of the following an exact or measured
  number?
• The number of chair legs in this room
• The length of your benchtop in inches
• The length of your benchtop in cm
• The area of the projector screen

Exact
Measured
Measured
Measured
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Using Conversion Factors
Your patient tells you that she recently lost 15
kg. How many pounds has she lost?

• Whats given? What do we want to
  know?
• What conversion factors do I need?
• Set up problem

weight lost (kg) 15 kg
weight lost (lb) ? lb
kg ? lb
2.20 lb 1 kg
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Using Conversion Factors
kg ? lb

• 3. Set up problem

15 kg
x
?
Check sig figs!
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Using Conversion Factors
The recommended daily value of vitamin C is 60
mg. If an average orange contains 45 mg of
vitamin C, how many oranges should you eat in a
week?

• Whats given? What do we want to
  know?
• What conversion factors do I need?

1 week
of oranges
week ? oranges
? days
? mg vitamin C
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Physical Properties of Materials

• Physical Property
• can be measured or perceived without changing the
  materials identity
• Intensive
• Independent of amount of substance
• Ex. Boiling point
• Extensive
• Depends on amount of substance
• Ex. Mass, volume

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Density

• Relationship between mass and volume

• Density is a physical property
• Density is an intensive property

4 times more mass 4 times more volume
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Density

• Units
• SI kg/m3
• often use g/L
• g/mL
• g/cm3
• g/cc
• Density of water (at 20C and typical room
  pressure)
• 1 g/cc 1 g/mL

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Density of Solids

• How can we determine the density of a solid?
• Need to know mass
• Need to know volume

Measure displacement of water
Does this method work for all solid materials?
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Density Table

• Density can be used as a conversion factor!
• (relates mass to volume)

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Specific Gravity (sp gr)

• Ratio between density of substance density of
  water

Measure sp gr with a hydrometer
Units for sp gr?
Unitless!
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Temperature

• Measure of how hot or cold a substance is
  relative to another substance
• Scales and Units

Scale Boiling Point H2O Freezing Point H2O
Celsius C
Fahrenheit F
Kelvin K
100C
0C
212F
32F
373.15 K
273.15 K
Note the unit is not K
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Temperature Conversions

• How many units are between boiling point and
  freezing point of water?

Scale
Celsius C
Fahrenheit F
Kelvin K
100C 0C
100 units
212F 32F
180 units
373 K 273 K
100 units
the unit 1 Kelvin equals the unit 1 degree
Celsius
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Converting Units Fahrenheit to Units Celsius
180 Fahrenheit degrees 100 Celsius degrees
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Things to Remember about the Temperature Scales

1. 0 K is absolute zero
2. You can never (ever ever ever) have a temperature
   of negative K
3. The unit for the Celsius scale is the degree C
   (C)
4. The unit for the Fahrenheit scale is the degree F
   (F)
5. The units for the Kelvin scale is the Kelvin (K)
6. A change of x Kelvin a change of x C

Start value and end values are different Both
changed the same amount (50 K units 50 C units)
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Precision and Accuracy

• Precision reproducibility
• Accuracy how close to actual value

Temp (C)