PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1

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PRINCIPLES OF CHEMISTRY I CHEM 1211 CHAPTER 1

DR. AUGUSTINE OFORI AGYEMAN Assistant professor
of chemistry Department of natural
sciences Clayton state university
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CHAPTER 1MEASUREMENT
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MEASUREMENT
- Is the determination of the dimensions,
capacity, quantity, or extent of something - Is
a quantitative observation and consists of two
parts a number and a scale (called a unit) - Is
the tool chemists use most Examples mass,
volume, temperature, pressure, length, height,
time
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SIGNIFICANT FIGURES
Precision - Provides information on how closely
individual (repeated) measurements agree with one
another Accuracy - Refers to how closely
individual measurements agree with the true
value (correct value) Precise measurements may
NOT be accurate
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SIGNIFICANT FIGURES
Exact Numbers - Values with no uncertainties -
There are no uncertainties when counting objects
or people (24 students, 4 chairs, 10 pencils) -
There are no uncertainties in simple
fractions (1/4, 1/7, 4/7, 4/5) Inexact Numbers
- Associated with uncertainties - Measurement
has uncertainties (errors) associated with it -
It is impossible to make exact measurements
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SIGNIFICANT FIGURES
Measurements contain 2 types of information -
Magnitude of the measurement - Uncertainty of the
measurement Only one uncertain or estimated
digit should be reported Significant Figures
digits known with certainty one uncertain
digit
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RULES FOR SIGNIFICANT FIGURES
1. Nonzero integers are always significant
4732 (4 sig. figs.) 875 (3 sig. figs.) 2.
Leading zeros are not significant 0.0045 (2
sig. figs.) 0.00007895 (4 sig. figs.) The
zeros simply indicate the position of the decimal
point 3. Captive zeros (between nonzero digits)
are always significant 1.0025 (5 sig figs.)
12000587 (8 sig figs)
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RULES FOR SIGNIFICANT FIGURES
4. Trailing zeros (at the right end of a number)
are significant only if the number contains a
decimal point 2.3400 (5 sig figs) 23400
(3 sig figs) 5. Exact numbers (not obtained
from measurements) are assumed to have
infinite number of significant figures
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RULES FOR SIGNIFICANT FIGURES
How many significant figures are present in each
of the following? What is the uncertainty in each
case? significant figures uncertainty 1.24
g 3 0.01 g 0.0024 L 2 0.0001
L 0.39200 mL 5 0.00001 mL 3.0026 kg
5 0.0001 kg
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RULES FOR SIGNIFICANT FIGURES
Rounding off Numbers 1. In a series of
calculations, carry the extra digits through
to the final result before rounding off to the
required significant figures 2. If the
first digit to be removed is less than 5, the
preceding digit remains the same (round down)
Round to two significant figures 2.53
rounds to 2.5 and 1.24 rounds to 1.2
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RULES FOR SIGNIFICANT FIGURES
Rounding off Numbers 3. If the first digit to be
removed is greater than 5, the preceding
digit increases by 1 (round up) (2.56 rounds
to 2.6 and 1.27 rounds to 1.3) 4. If the
digit to be removed is exactly 5 (round even) -
The preceding number is increased by 1 if that
results in an even number (2.55 rounds to 2.6
and 1.35000 rounds to 1.4) - The preceding
number remains the same if that results in an
odd number (2.45 rounds to 2.4 and
1.25000 rounds to 1.2)
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RULES FOR SIGNIFICANT FIGURES
- The certainty of the calculated quantity is
limited by the least certain measurement, which
determines the final number of significant
figures
Multiplication and Division - The result contains
the same number of significant figures as the
measurement with the least number of significant
figures 2.0456 x 4.02 8.223312 8.22 3.20014
1.2 2.6667833 2.7
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RULES FOR SIGNIFICANT FIGURES
- The certainty of the calculated quantity is
limited by the least certain measurement, which
determines the final number of significant
figures
Addition and Subtraction - The result contains
the same number of decimal places as the
measurement with the least number of decimal
places
4.03
6.00 (not 6)
5.5
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SCIENTIFIC NOTATION
- Used to express too large or too small numbers
(with many zeros) in compact form - The product
of a decimal number between 1 and 10 (the
coefficient) and 10 raised to a power
(exponential term) 24,000,000,000,000 2.4 x
1013
exponent (power)
coefficient
exponential term
0.000000458 4.58 x 10-7
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SCIENTIFIC NOTATION
- Provides a convenient way of writing the
required number of significant figures 6300000
to 4 significant figures 6.300 x 106 2400 to
3 significant figures 2.40 x 103 0.0003 to 2
significant figures 3.0 x 10-4
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SCIENTIFIC NOTATION
- Add exponents when multiplying exponential
terms (5.4 x 104) x (1.23 x 102) (5.4 x 1.23)
x 10 42 6.6 x 106 - Subtract exponents when
dividing exponential terms (5.4 x 104)/(1.23 x
102) (5.4/1.23) x 10 4-2 4.4 x 102
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MEASUREMENT SYSTEMS
Two measurement systems English System of
Units (commercial measurements) pound, quart,
inch, foot, gallon Metric System of Units
(scientific measurements) SI units (Systeme
International dUnites) liter, meter, gram More
convenient to use
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FUNDAMENTAL (BASE) UNITS
Physical Quantity Mass Length Time Temperature Am
ount of substance Electric current Luminous
intensity
Name of Unit Kilogram Meter Second Kelvin Mole Am
pere Candela
Abbreviation kg m s (sec) K mol A cd
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DERIVED UNITS
Area length x length m x m m2 Volume m x
m x m m3 Volume may also be expressed in LITERS
(L) 1L 1000 mL 1000 cm3 or cubic centimeters
(c.c.) Implies 1mL 1c.c. mL is usually used
for volumes of liquids and gases c.c. is usually
used for volumes of solids Density kg/ m3
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DERIVED UNITS
Physical Quantity Force Pressure Energy Power Fr
equency
Name of Unit Newton Pascal Joule Watt Hertz
Abbreviation N (m-kg/s2) Pa (N/m2 kg/(m-s2) J
(N-m m2-kg/s2) W (J/s m2-kg/s3) Hz (1/s)
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UNIT CONVERSIONS
Prefix Giga Mega Kilo Deci Centi Milli Micro Nano
Pico Femto
Abbreviation G M k d c m µ n p f
Notation 109 106 103 10-1 10-2 10-3 10-6 10-9 10-
12 10-15
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UNIT CONVERSIONS
1 gigameter (Gm) 1 megameter (Mm) 1 kilometer
(km) 1 decimeter (dm) 1 centimeter (cm) 1
millimeter (mm) 1 micrometer (µm) 1 nanometer
(nm) 1 picometer (pm) 1 femtometer (fm)
109 meters 106 meters 103 meters
10-1 meter 10-2 meter 10-3 meter
10-6 meter 10-9 meter 10-12 meter
10-15 meter
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UNIT CONVERSIONS
Length/Distance 2.54 cm 1.00 in. 12 in. 1
ft 1 yd 3 ft 1 m 39.4 in. 1 m 1.09 yd 1 km
0.621 mile 1 km 1000 m
Time 1 min 60 sec 1 hour 60 min 24 hours 1
day 7 days 1 week
Volume 1 gal 4 qt 1 qt 0.946 L 1 L 1.06
qt 1 L 0.265 gal 1 mL 0.034 fl. oz.
Mass 1 Ib 454 g 1 Ib 16 oz 1 kg 2.20 lb 1
oz 28.3 g
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UNIT CONVERSIONS
Conversion Factors
1 km 1000 m
or

1 L 1000 mL

or
or
24 hours 1 day

1 kg 2.20 lb

or
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UNIT CONVERSIONS
given number unit
new unit
new number new unit
unit to be converted
quantity to be expressed in new units
quantity now expressed in new units
conversion factor
given data
desired unit
answer in desired unit
unit of given data
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UNIT CONVERSIONS
Convert 34.5 mg to g
How many gallons of juice are there in 20.0
liters of the juice?
Convert 4.0 gallons to quarts
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UNIT CONVERSIONS
Convert 2.64 µg to kg
Convert 3.912 m2 to km2
Convert 4.0 cm3 to µm3
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DENSITY
- The amount of mass in a unit volume of a
substance
Ratio of mass to volume
Density
Units Solids grams per cubic centimeter
(g/cm3) Liquids grams per milliliter
(g/mL) Gases grams per liter (g/L) - Density of
2.3 g/mL implies 2.3 grams per 1 mL - Density
usually changes with change in temperature
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DENSITY
For a given liquid - Objects with density less
than that of the liquid will float - Objects
with density greater than that of the liquid will
sink - Objects with density equal to that of the
liquid will remain stationary (neither float nor
sink)
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DENSITY
The liquid level in a graduated cylinder reads
12.20 mL. The level rises to 18.90 mL when 129.31
g of piece of gold is added to the cylinder.
What is the density of gold? Volume of the
piece of gold 18.90 mL 12.20 mL 6.70
mL Mass of the piece of gold 129.31 g Density
mass/volume 129.31 g/6.70 mL 19.3 g/mL or
19.3 g/cm3
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TEMPERATURE
- The degree of hotness or coldness of a body
or environment 3 common temperature scales
Metric system Celsius and Kelvin English
system Fahrenheit Celsius Scale (oC) Reference
points are the boiling and freezing points of
water (0oC and 100oC) - 100 degree
interval Kelvin Scale (K) Is the SI unit of
temperature (no degree sign) The lowest
attainable temperature on the Kelvin scale is 0
(-273 oC) referred to as the absolute zero
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TEMPERATURE
Fahrenheit Scale Water freezes at 32oF and boils
at 212oF - 180 degree interval
or
or
10o, 40o, 60o may be considered as 2 significant
figures 100o may be considered as 3 significant
figures
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TEMPERATURE
Convert 29 oC to K
Convert 29 K to oC
Convert 29 oF to oC
Convert 29 oC to oF