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Unformatted text preview: Chapter 1
Chapter
Introduction: Some Basic Concepts
Welcome to the World of
Welcome
Chemistry
Chemistry Chemistry
Chemistry
The study of matter – its nature, its structure
The
(how it is related to its atoms and
molecules), properties, transformations,
and its interactions with energy
and
Gold Mercury Matter
Matter
Anything that has mass
Anything
and occupies space
and Mass vs Weight
Mass
weight = force = mg
g: gravitational acceleration
g:
s Mass is a measurement of the
Mass
quantity of matter in a body or
sample
sample
s Weight is the magnitude of Earth’s
Weight
attraction to such a body or sample
attraction
s Physical States (Phases)
Physical Solid
Solid definite shape and volume
s made of particles (atoms, molecules, or
made
ions) held close together and rigidly in
place
place
s reasonably well understood.
Example:
s Graphite — layer
structure of carbon
atoms reflects
physical properties.
physical Liquid
Liquid
definite volume but
definite
indefinite shape
indefinite
s made of particles
made
(atoms, molecules, or
ions) held close together
but allowed to move
relative to each other
s fluid and may not fill a
fluid
container completely
s not well understood
not
s Gas
Gas
s s s s
s indefinite volume and
indefinite
indefinite shape
indefinite
the same shape and
the
volume as their container
made of particles (atoms or
made
molecules) separated from
each other by large
distances and that move
very fast
very
fluid
good theoretical
good
understanding
understanding Physical Property
Physical
s s s characteristic of matter
characteristic
that can be observed
without changing the
basic identity of the
matter
matter
characteristics that are
characteristics
directly observable
directly
eg. state, size, mass,
eg.
V, color, odor, melting
point (Tm), boiling point
point
),
(Tb), density,
(T ),
solubility...
solubility... Chemical Property
Chemical
characteristic of matter that requires
characteristic
change in identity of the matter for
observation (a chemical reaction)
s characteristic that describes the
characteristic
behavior of matter
behavior
s s eg. flammability, corrosiveness,
eg.
bleaching power, explosiveness, ...
bleaching Scientific Method
Scientific
Observation Hypothesis *
Law * * Theory * experiment and then modify
experiment s s s Hypothesis – a tentative interpretation or
explanation for an observation
explanation
– falsifiable – confirmed or refuted by other
falsifiable
observations
observations
– tested by experiments – validated or
tested
invalidated
invalidated
when similar observations are consistently
when
made, it can lead to a Scientific Law
Scientific
– a statement of a behavior that is always
statement
observed
observed
– summarizes past observations and
summarizes
predicts future ones
predicts
– Law of Conservation of Mass
A theory is a unifying principle that explains
a body of facts and the laws based on them.
It is capable of suggesting new hypotheses.
It Classification of Matter
Classification Mixture
Mixture
A combination of pure substances in
combination
which the components retain their
identities (no reaction)
identities
s Can be separated into simpler
Can
mixtures and/or pure substances by
mixtures
s Physical Separation Methods
Physical
s
s
s s
s mechanical: eg. sand and iron filings
filtration: eg. sand and water
extraction: eg. washing clothes, decaffeinating
extraction:
coffee
coffee
distillation
chromatography Distillation
Distillation
s Simple  for separation of volatile component
Simple
from nonvolatile component(s)
from Distillation
Distillation
s Fractional  for separation of multiple
Fractional
volatile components from each other.
Employed in many chemistry labs,
labs, and in crude oil refining.
labs, Chromatography
Chromatography
s Mixture placed in mobile phase (gas
Mixture
or liquid). Mobile phase flows over
and through stationary phase (solid
or liquid). Mixture components
separate based on relative affinity for
mobile and stationary phases.
mobile Heterogeneous Mixture
Heterogeneous
inconsistent composition
inconsistent
s atoms or molecules mixed not uniformly
s contains regions within the sample with
contains
different characteristics
different
s eg. pizza, carpet, beach sand, ...
s Homogeneous Mixture
solution
s consistent composition throughout
consistent
s atoms or molecules mixed uniformly
s eg. air in a room, glass of tap water
s Compound
Compound
can be broken down to 2 or more
can
elements by chemical means
elements
s constant composition
s eg. water, H2O, by mass H:O = 1:8
s hydrogen peroxide, H2O2, H:O = 1:16
hydrogen
elements combined lose individual
elements
identities
identities
s more than 20 million compounds are
more
now known
now
s Elements
Elements
s s s
s
s basic substances of
basic
which all matter is
composed
composed
pure substances that
pure
cannot be decomposed
by ordinary means to
ordinary
other substances.
other
made up of atoms
~ 117 known at this time
given name and chemical
given
symbol
symbol Aluminum Bromine Element Symbols
Element
1, 2 or 3 letters:
1,
s first letter always capitalized
first
always
s usually first letter(s) of name
s H hydrogen
C carbon
O oxygen
N nitrogen
oxygen
nitrogen
Na sodium
Cl chlorine Mg magnesium
Al aluminum P phosphorus K potassium
Po polonium
Po learn Latin names where appropriate,
learn
antimony  Sb  stibium
antimony
gold  Au  aurum
gold
tungsten  W – wolfram
tungsten
sodium – Na – natrium
sodium
potassium – K  kalium
potassium
s elements from 104 to 111 are named
elements
after scientists; 112118 have 3 letter
symbols based on Latin name for
number
number
s 112
112
113
114
115
116 Uub
Uut
Uuq
Uup
Uuh ununbium
ununtrium
ununquadium
ununpentium
ununhexium Homework: learn the names of
first 36 elements in the periodic table
first Periodic Table
Periodic
a listing of the elements arranged
listing
according to their atomic numbers,
chemical and physical properties
chemical
s VERY useful and important
s Physical Change
Physical
transformation of matter from one
transformation
state to another that does not involve
change in the identity of the matter
change
s examples: boiling, subliming,
examples:
melting, dissolving (forming a
solution), ...
solution),
s Chemical Change
Chemical
s s transformation of matter from one state to another
transformation
that involves changing the identity of the matter
that
examples: rusting (of iron), burning (combustion),
examples:
digesting, formation of a precipitate, gas forming,
acidbase neutralization, displacing reactions...
acidbase Intensive Property
Intensive
independent of amount of matter
s eg. density, temperature,
eg.
concentration of a solution, specific
heat capacity...
heat
s Extensive Property
Extensive
depends on amount of matter
s eg. mass, volume, pressure, internal
eg.
energy, enthalpy, ...
energy,
s Density
Density
s s
s mass (g)
mass (g)
mass
Density = = Density
volume (cm3)
volume (mL)
volume
density of H2O is 1.00 g/cm3 (pure water at ~ 4 °C)
(pure
1cm3 = 1mL
Mercury Platinum Aluminum liquid
13.6 g/cm3 21.5 g/cm3 They sink in water 2.7 g/cm3 Know and Own and Practice
Well
Well
Metric System
s SI Units
s Unit Conversions
s Learn a Conversion Factor Between
Learn
English and Metric for
English
– length, mass, volume, pressure
s Prefixes
Prefixes
A prefix
prefix
n
s iin front of a unit increases or decreases the size
of that unit. s makes units larger or smaller than the initial unit
makes
by one or more factors of 10.
s indicates a numerical value. prefix
1 kilometer
kilo =
= value
1000 meters
1000 1 kilogram
kilo = 1000 grams
grams Metric and SI Prefixes
Metric Learning Check
Learning
Indicate the unit that matches the description.
1. A mass that is 1000 times greater than 1
1.
gram.
gram.
1) kilogram 2) milligram 3) megagram
1)
2. A length that is 1/100 of 1 meter.
1) decimeter 2) centimeter
3) millimeter
1)
3. A unit of time that is 1/1000 of a second.
1) nanosecond
2) microsecond
3) millisecond
3) Learning Check
Learning
Select the unit you would use to measure
Select
A. your height.
A.
1) millimeters 2) meters
1) 3) kilometers B. your mass.
B.
1) milligrams 2) grams
1) 3) kilograms C. the distance between two cities.
1) millimeters 2) meters
3) kilometers
1)
D. the width of an artery.
1) millimeters 2) meters
1) 3) kilometers Volume
Volume
1 m = 10 dm
10
(1m)3 = (10 dm)3
1m3 = 1000 dm3 = 1000 L
1m
1 dm = 10 cm
(1dm)3 = (10 cm)3
1dm3 = 1000 cm3 = 1000mL Equalities
Equalities
Equalities
• use two different units to describe the same
use
measured amount.
• are written for relationships between units of
are
the metric system, U.S. units, or between
metric and U.S. units.
For example,
1m
= 1000 mm
1000
1 llb
b
= 16 oz
2.205 lb = 1 kg
1L
= 1.057 qt
1 hour = 60 min Conversion Factors
Conversion
A conversion factor
conversion
• is a fraction obtained from an equality.
Equality: 1 in. = 2.54 cm
in. s
• iis written as a ratio with a numerator and
denominator.
denominator. • can be inverted to give two conversion factors
can
for every equality.
for
1 in.
and 2.54 cm
in.
and
2.54 cm
1 in.
2.54 Learning Check
Learning
Write conversion factors for each pair of units.
A. liters and mL Equality: 1 L = 1000 mL B. hours and minutes Equality: 1 hr = 60 min C. meters and kilometers
C.
Equality:
Equality: 1 km = 1000 m D. micrograms and grams
Equality:
Equality: 1 µg = 106 g Conversion Factors in a Problem
Conversion
A conversion factor
conversion
• may be obtained from information in a word
may
problem.
problem.
s
• iis written for that problem only.
for
Example 1:
Example
The price of one pound (1 lb) of red peppers is
one
$2.39.
$2.39.
1 lb red peppers
and
$2.39
$2.39
$2.39
1 lb red peppers
$2.39
Example 2:
The cost of one gallon (1 gal) of gas is $3.95.
one
$3.95.
1 gallon of gas
and
$3.95
$3.95
$3.95
1 gallon of gas
$3.95 Percent as a Conversion Factor
Percent
A percent factor
percent • gives the ratio of the parts to the whole.
%= •
•
• Parts x 100
Whole
uses the same unit to express the percent.
uses the value 100 and a unit for the whole.
can be written as two factors.
can
Example: A food contains 30% (by mass) fat.
Example:
30 g fat
100 g food and 100 g food
30 g fat Density as a conversion factor
Density
Density of a mineral oil = 0.875 g/mL
0.875 g oil
1 mL
mL and 1 mL
mL
0.875 g oil Learning Check
Learning
Write the equality and conversion factors for
each of the following.
A. square meters and square centimeters
B. jewelry that contains 18% (by mass) gold
C. One gallon of gas is $4.00 Solving: Given and Needed Units
Given
To solve a problem
dentify
• IIdentify the given unit
given unit
dentify
• IIdentify the needed unit.
needed
Example: A person has a height of 2.0 meters.
What is that height in inches?
What
The given unit is the initial unit of height.
given
given unit = meters (m)
given
The needed unit is the unit for the
needed
answer.
answer.
needed unit = inches (in.)
needed Problem Setup: Dimensional Analysis
Dimensional • Write the given and needed units.
• Write a unit plan to convert the given unit
Write
to the needed unit.
to
• Write equalities and conversion factors
Write
that connect the units.
that
• Use conversion factors to cancel the given
Use
unit and provide the needed unit.
unit
Unit 1
Unit x Given
Given
unit x Unit 2
= Unit 2
Unit
Unit 1
Unit
Conversion = Needed
Conversion
factor
unit Setting up a Problem
Setting
How many minutes are 2.5 hours?
Given unit
=
2.5 hr
2.5
Needed unit =
min
Unit Plan =
hr → min
Setup problem to cancel hours (hr).
Setup
Given Conversion
Needed
Given
unit
factor
unit
2.5 hr x 60 min
= 150 min (2 SF)
2.5
1 hr
hr Learning Check
Learning
A rattlesnake is 2.44 m long. How many
centimeters long is the snake?
1) 2440 cm
1) 2440
2) 0.0244 cm
3) 24.4 cm
4) 244 cm
4) Using Two or More Factors
Using
• Often, two or more conversion factors are
Often,
required to obtain the unit needed for the answer.
required
Unit 1
Unit → Unit 2 → Unit 3
Unit • Additional conversion factors are placed in the
Additional
setup to cancel each preceding unit
setup
Given unit x factor 1 x factor 2 = needed unit
Given
needed
Unit 1 x Unit 2
Unit
Unit 1
Unit x Unit 3
Unit
Unit 2 = Unit 3
Unit Example: Problem Solving
Example:
How many minutes are in 1.4 days?
Given unit: 1.4 days
Given
Factor 1
Factor Plan:
Plan: days → Factor 2 hr → min Set up problem:
Set
1.4 days x 24 hr x 60 min = 2.0 x 103 min
24
60
min
1day
1 hr
1day
2 SF
SF Exact Exact = 2 SF
SF Learning Check
Learning
A bucket contains 4.65 L of water. How
bucket
many
many
gallons of water is that?
Unit plan: L
→
qt
→ gallon
Equalities: 1.06 qt = 1 L
Set up Problem:
Set
4.65 L x
4.65
3 SF 1.06 qt
1L
Exact 1 gal = 4 qt x 1 gal = 1.23 gal
gal
4 qt
Exact
3 SF Learning Check
Learning
If a ski pole is 3.0 feet in length, how long is the ski
If
pole in mm?
Solution:
Solution:
3.0 ft x
3.0 12 in x 2.54 cm x 10 mm =
2.54
10
1 ft
1 in.
1 cm
ft
Calculator answer: 914.4 mm
Calculator
Needed answer:
910 mm (2 SF rounded)
Needed
Check factor setup: Units cancel properly
Check
Units
Check needed unit: mm Learning Check
Learning If your pace on a treadmill is 65 meters per minute,
how many minutes will it take for you to walk a
distance of 7500 feet?
Solution:
Solution:
Given: 7500 ft 65 m/min Needed: min
Plan:
ft
→ in. →
cm →
m → min
Equalities: 1 ft = 12 in. 1 in. = 2.54 cm 1 m = 100 cm
1 min = 65 m (walking pace)
min
Set Up Problem:
7500 ft x 12 in. x
7500
12
1 ft
ft 2.54 cm x 1m
x 1 min
2.54
min
1 in.
100 cm
65 m = 35 min final answer (2 SF)
35
final (# 11): Ethylene glycol, C2H6O2, iis an ingredient of
s
(#
automobile antifreeze. Its density is 1.11 g/cm3 at 20
automobile
°C. If you need exactly 500. mL of this liquid, what
mass of the compound, in grams, is required?
mass Needed: m(g) Given: d(g/cm3) and V(mL) 1 cm3 = 1 mL
cm
1.11 g
1.11
500. mL × ───── = 555 g
500.
─────
1 mL
3 SF
SF (# 13): A chemist needs 2.00 g of a liquid compound
with a density of 0.718 g/cm3. What volume of the
with
What
compound is required?
compound Needed: V(cm3) Given: d(g/cm3) and m(g) 1 cm3
cm
2.00 g × ────── = 2.78 cm3
──────
0.718 g
3 SF
SF (# 15): A sample of 37.5 g of unknown metal is placed in a
graduated cylinder containing water. The levels of the
water before and after adding the sample are 7.0 and 20.5
mL respectively. Which metal in the following list is most
likely the sample?
likely Metal d(g/mL) Metal d(g/mL) Mg
Mg 1.74 Al 2.70 Fe
Fe 7.87 Cu 8.96 Ag
Ag 10.5 Pb 11.3
11.3 The volume of sample = volume of water
displaced in cylinder = 20.5 – 7.0 = 13.5 mL
displaced
one dec. place
one After
After
placing the
piece of
metal
metal Before
Before (# 15):
(# Needed: d(g/cm3) Given: V(mL) and m(g) m
37.5 g
37.5
d = ── = ────── = 2.78 g/mL
── ──────
V
13.5 mL
13.5
3 SF
SF
From the list, the metal is Al. s Accuracy: nearness of the
nearness
measurement to accepted value of
the quantity.
the s Precision: reproducibility; how well
reproducibility;
several determinations of the same
quantity agree.
quantity Consider a sample that was analyzed for
lead content and was known to contain 49.3 ppm
ppm
lead. Two analyses
lead. Two
Analysis A
Analysis B
diff. from
Analysis
diff.
Trial
ppm Pb
Trial
ppm Pb
Trial
average
average
1
38.9
1
48.9
4.6
2
23.2
2
59.8
6.3
3
55.9
3
54.5
1.0
4
80.1
4
49.0
4.5
5
46.9
5
55.3
1.8
46.9
average = 49.0 ppm Pb
53.5 ppm
average diff. 15.5 ppm 3.6 ppm Numbers
Numbers
magnitude, value
s direction: sign (+ or −)
s type of measurement: units
s precision of original measurement:
precision
significant figures
significant
s Measured Numbers
Measured
A measuring tool
measuring
is used to determine
a quantity such as
height or the mass
of an object.
of
• provides numbers
provides
for a measurement
called measured
numbers.
numbers Reading a Meter Stick
Reading
. l2. . . . l . . . . l3 . . . . l . . . . l4. .
cm
cm
• The markings on the meter stick at the end
The
of the orange line are read as
of
the first digit
2
the •
• plus the second digit 2.7
The last digit is obtained by estimating.
The
estimating
The end of the line might be estimated
between 2.7–2.8 as halfway (0.5) or a little
more (0.6), which gives a reported length
of 2.75 cm or 2.76 cm.
of Known & Estimated Digits
Known
In the length reported as 2.76 cm,
In • The digits 2 and 7 are certain
The
•
• (known).
The final digit 6 was estimated
The
(uncertain).
All three digits (2.76) are
All
significant including the estimated
digit.
digit. Significant Figures in
Measured Numbers
Measured
Significant figures • obtained from a measurement
obtained
include all of the known digits
plus the estimated digit.
plus • reported in a measurement
reported
depend on the measuring tool.
depend Significant Figures
Significant Examples of Counting SF
Examples
143.22
s 143.0
s 300592
s 0.0020930
s 100.0
s 100.
s 100 s s s Exact numbers have an
unlimited number of significant
figures
A number whose value is
number
known with complete certainty
is exact
exact
– from counting individual
from
objects
objects
– from definitions
1 cm is exactly equal to 0.01 m
– from integer values in
from
equations
equations
in the equation for the radius
in
of a circle, the 2 is exact
of SF in Calculations
SF
Addition and/or Subtraction
s perform operation s round answer to same number of
round
digits after decimal as number in
calculation with the fewest
calculation Example
Example
132.09 + 35.94376 – 0.0173 = 132.09 + 35.94376 – 0.0173 =
132.
168.01646
168.01646
must have 2 digits after decimal
168.02 Multiplication and/or
Division
Division
s perform operation(s) s round answer to same number of
round
significant figures as number in the
calculation with the fewest
calculation Example
Example
(26.894)(0.0837)/13 =
(26.894)(0.0837)/13
(26.894)(0.0837) = 0.1731560
(26.894)(0.0837)
13
13
must have 2 SF
0.17 Log and/or Antilog
Log
number of digits in mantissa of log =
number
digits
number of significant figures in antilog
in Example
Example
log (14.8003) =
log log (14.8003) = 1.17027051857
log
antilog
antilog 1.170271
1.
mantissa
mantissa Rounding
Rounding
s if
if first digit to be eliminated is ≥ 5,
round preceding digit up one
round s if
if first digit to be eliminated is <5,
truncate
truncate Examples
Examples
Round each of the following to 4 SF
Round
SF
s 10.02700
10.03
10.03
s 10.02495
10.02
10.02
s 10.02502
10.03
10.03 10.02500
10.03
10.03
s 10.01500
10.02
10.02
s 10.02500000000000000000000001
10.03
10.03
s Exponentials
Exponentials
Scientific notation: very large or very small
Scientific
numbers are expressed in the following
general form:
exponent term, n = ± integer
integer N x 10n
10
digit term, between ± 1 and 9.9999…
(coefficient)
(coefficient)
eg
eg −12,760,000 = −1.276 x 10 7
0.000012760 = 1.2760 x 105
0.000012760 Write the following in scientific notation:
Write
22,400 = 2.24 x 104
22,400 2.24
22,400. = 2.2400 x 104
22,400. 2.2400
892 x 105 = 8.92 x 107
8.92
0.00198 x 1010 = 1.98 x 1013
1.98
127.60 x 105 = 1.2760 x 103
1.2760
Write in fixed notation:
Write
5.720 x 102 = 0.05720
5.720
0.05720
1.982 x 104 = 19,820
19,820 Exponentials in calculations
Exponentials
5.750 x 103 + 7.25 x 102 = 1.75 x 103 x 6.45 x 102
57.50 x 102 + 7.25 x 102
57.50 = 1.75 x 103 x 6.45 x 102
64.75 x 102
64.75 = 1.75 x 103 x 6.45 x 102
64.75
1.75 x 6.45 x 102
103 x 102 = 5.74 x 103
5.74
3 SF
SF (0.000345 – 0.0001273) x 6.730x10 3
(0.000345 = 154.00
6 dec places (we keep the 77, though)
0.0002177 x 6.730x103
0.000217 = 154.00
154.00
2.177 has 3 SF only
2.17 has
2.177x10−4 x 6.730x103
2.17 = 0.009513 = 9.51x10−3 0.00951
1.5400 x 102
3 SF
1.5400
SF Temperature
Temperature
Temperature
Temperature
s
• iis a measure of how hot or
cold an object is compared
to another object.
to
ndicates
• iindicates that heat flows
from the object with a
higher temperature to the
object with a lower
temperature.
s
• iis measured using a
thermometer.
thermometer. Temperature Scales
Temperature
Temperature
Temperature
Scales
Scales
s are
Fahrenheit,
Celsius, and
Kelvin.
s have reference
points for the
boiling and
freezing points
of water. Temperature Scales
Temperature
s Fahrenheit (°F ) s Celcius or Centigrade (°C ) s 9
°F = ── °C +32 = 1.8 °C + 32
°F ──
5 s 5
(°F  32)
(°F
°C = (°F 32) = °C
9
1.8
1.8 s K = °C + 273
°C Kelvin (K) 273.15 (exact) ΔT(K) = ΔT(°C) variation of temperature
K) Learning check
Learning
a. The normal temperature of a chickadee is
105.8°F. What is that temperature on the
Celsius scale?
Celsius
1) 73.8°C 2) 58.8°C
3) 41.0°C
3)
b. A pepperoni pizza is baked at 235°C. What
temperature is needed on the Fahrenheit
temperature
Fahrenheit
scale?
1) 267°F
2) 508°F
3) 455°F
1)
3)
c. Convert 204.3 K into °C. Other elements to
remember
remember
Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn
s Ru, Rh, Pd, Ag, Cd
s Pt, Au, Hg
s ...
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This note was uploaded on 11/07/2011 for the course CHM 2045 taught by Professor Geiger during the Fall '08 term at University of Central Florida.
 Fall '08
 geiger
 Chemistry, Atom, Mole

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