Transcript Chapter 1 - faculty at Chemeketa

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Major divisions of Chemistry
 General
 Inorganic
Elements besides Carbon
 Analytical
Methods of analysis
 Physical
Theory and concepts
Organic
Carbon based compounds
 Biochemistry
Chemistry of living things
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Chapter 1:
Measurement
Units of Measurement
Conversion Calculations
Density
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Measurements in chemistry
See Handout Sheet of
Units of Measurements
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Units of Measurement
Metric
SI
Common
Conversions
Length
meter (m)
1 m = 1.09 yd
Volume
Mass
liter (L)
1 L = 1.06 qt
gram (g)
1 kg = 2.2 lb
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Matter
=The stuff things are made of.
(Air, water, rocks, etc..)
Matter has Mass and takes up space.
=The amount of stuff (in g’s)
(Bowling Ball > Balloon)
Weight on earth.
=Pull of Gravity on matter.
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Mass Vs. Weight
How much would you weigh
on another planet?
http://www.exploratorium.edu/ronh/weight/
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Scientific notation
If a number is larger than 1
• Move decimal point X places left to get a
number between 1 and 10.
1 2 3 , 0 0 0 , 0 0 0.
=
1.23 x 108
•The resulting number is multiplied by 10X.
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Scientific notation
If a number is smaller than 1
• Move decimal point X places right to get
a number between 1 and 10.
0. 0 0 0 0 0 0 1 2 3
=
1.23 x 10-7
•The resulting number is multiplied by 10-X.
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Examples
Write in Scientific Notation:
25 =
8931.5 =
0.000593 =
0.0000004 =
3,210. =
2.5  10 1
8.9315  10 3
5.93  10 - 4
4  10 - 7
3.210  103
Do not press this on your calculator!
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Scientific notation
1.44939 × 10-2 =
1.44939E -2
0.0144939
On Calculator
×10
1.44939 EE (-) 2
Means
×10
Change
Sign
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Measured & Exact Numbers
Exact Numbers =
from counting or by definition
12 coins per package
12 coins
1 package
=
1 package
12 coins
12 coins
1 dozen coins
=
1 dozen coins
12 coins
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Measured & Exact Numbers
Measured Numbers =
estimated using a tool
All measurements contain some uncertainty.
• We make errors
• Tools have limits
1
2
3
4
5
6
7
8
9
cm
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Accuracy
How close are we
to the true value?
Truth
Precision
How well do our
values agree?
Consistency
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Significant figures
Length of object is between 6.7 and 6.8
The next digit would be a guess.
1
2
3
4
5
6
7
8
9
cm
If use 6.76 then have error of + 0.01cm
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Metric prefixes
Changing the prefix alters the size of a unit.
Prefix Symbol
Factor (multiple)
mega
M
106
1,000,000
kilo
k
103
1,000
100
1
deci
d
10-1
0.1
centi
c
10-2
0.01
milli
m
10-3
0.001
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Problem Solving Using
Conversion Factors
Many problems require a change of
one unit to another unit by using
conversion factors (fractions).
unit1 × conversion factor = unit2
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How many feet are there in 22.5 inches?
The conversion factor must
unit
factor = unit2
accomplish
two things:
1 × conversion
inches × conversion factor = feet
It must cancel
inches.
It must
introduce feet
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The conversion factor takes a fractional
form.
ft
in 
= ft
in
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Putting in the measured value and the
ratio of feet to inches produces:
1ft
22.5in 
= ft
12in
= 1.875 ft
= 1.88 ft
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Convert 3.7×1015 in to miles.
Inches can be converted to miles by writing
down conversion factors in succession.
in  ft  miles
3.7  10 in
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1 mile
1 ft
10
x
x
= 5.8 10 miles
5280 ft
12 in
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Convert 4.51030 cm to kilometers.
Centimeters can be converted to kilometers by
writing down conversion factors in succession.
cm  m  km
1 km
1m
25
x
4.5  10 cm x
= 4.5  10 km
100 cm 1000 m
30
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Conversion of units
Examples:
10.7 T = ? fl oz
62.04 mi = ? in
5 kg = ? mg
9.3 ft = ? cm
5.7 g/ml = ? lbs/qt
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Conversion of units
Examples:
10.7 T = ? fl oz
1 fl oz
10.7 T x
= 5.35 fl oz
2T
62.04 mi x
62.04 mi = ? in
5.5 kg = ? mg
9.3 ft = ? cm
5280 ft 12 in
x
= 3.931106 in
1 mi
1 ft
or 3931000 in
5.5 kg x
9.3 ft
5.7 g/ml = ? lbs/qt
x
1000 g 1000 mg
x
= 5.5 106 mg
1 kg
1g
12 in 2.54 cm
x
= 280 in (not 280.)
1 ft
1 in
12 lb
1 lb
1L
5.7 g
1000 ml

x
x
x
1.06 qt 1 qt
1 ml 454 g
1L
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Density =
Density
Mass
Volume
1cc = 1 cm3 = 1 ml = 1 g water
g
cm3 or
Water 1.0
Air
0.0013
Gold 19.3
g
ml
Urine
Bone
Oil
o
At 4 C
1.01 - 1.03
1.7 - 2.0
0.8 - 0.9
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Density calculation
What is the density of 5.00 ml of
serum if it has a mass of 5.230 g?
d =m
V
V =m
d
d = 5.230 g
5.00 ml
m=Vd
= 1.05 g
ml
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Specific gravity
density of substance g
Specific Gravity =
ml
density of reference g
ml
Reference
commonly
water at
4oC
•Specific Gravity is unitless.
•At 4oC, density = specific gravity.
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Specific gravity
Hydrometer
•Commonly used to test
sugar in urine.
•Float height will be
based on Specific
Gravity.
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Density as a Conversion
A liquid sample with a density of 1.09 g/mL is
found to weigh 7.453 grams. What is the
volume of the liquid in mLs?
• Identify any conversion factors.
• What is unique to the problem?
7.453 g 1.0 ml = 6.837614 ml = 6.84 ml
1.09 g
•How should the answer look?
1.09 g
1 ml
1 ml
1.09 g
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