Course:
Instructor:
Office location:
Office phone:
Office hours:
General Chemistry I (CHEM 140, Section: 02)
Cevdet Akbay
LS 227
672-1943
MTWRF 10:00 AM-12:00 PM or by appointments
Chemistry:
The Study of Change
Chapter 1
Why ice melts and water evaporates?
Why keeping foods cold slows their spoilage?
How our bodies use food to maintain life?
Why leaves turn colors in the fall?
How a battery generates electricity?
How Blah blah blah
Chemistry supplies answers to these questions and
countless others like them. Then, how we define
Chemistry? It depends:
Chemistry is the study of the properties of materials
and the changes that materials undergo.
Chemistry is the scientific discipline that treats the
composition, properties, and transformations of
matter.
One of the joys of learning chemistry is
seeing how chemical principles operate in all
aspects of our lives, from lighting a match to
the development of drugs to cure cancer.
You are just beginning the journey of learning
chemistry.
This first chapter provides an overview of what
chemistry is about and deals with some
fundamental concepts of matter and scientific
measurements.
Chemistry is the study of matter and the
changes it undergoes (another definition)
1. Matter is anything that occupies space
and has mass.
2. A substance is a form of matter that has a
definite composition and distinct
properties.
water, ammonia, sucrose, gold, oxygen
A mixture is a combination of two or more substances
in which the substances retain their distinct identities.
1. Homogenous mixture – composition of the
mixture is the same throughout.
air, soft drink, milk, solder
2. Heterogeneous mixture – composition is not
uniform throughout.
cement,
iron filings in sand
Physical means can be used to separate a mixture
into its pure components.
distillation
magnet
An element is a substance that cannot be
separated into simpler substances by chemical
means.
• 115 elements have been identified
• 83 elements occur naturally on Earth
gold, aluminum, lead, oxygen, carbon
• 32 elements have been created by scientists
technetium, americium, seaborgium
These elements vary widely in their abundance, as shown in Figure 1.6.
Figure 1.6 Elements in percent by mass in (a) Earth's crust (including oceans and
atmosphere) and (b) the human body.
Some of the more familiar elements are listed in Table 1.2, along with the
chemical abbreviations—or chemical symbols—used to denote them.
The symbol for each element consists of one or two letters, with the first
letter capitalized. These symbols are often derived from the English name
for the element, but sometimes they are derived from a foreign name
instead (last column in Table 1.2).
All the known elements and their symbols are listed on the front inside
cover of this text. The table in which the symbol for each element is
enclosed in a box is called the periodic table.
A compound is a substance composed of atoms
of two or more elements chemically united in fixed
proportions.
Compounds can only be separated into their
pure components (elements) by chemical
means.
Water (H2O)
Glucose (C6H12O6)
Ammonia (NH3)
Most elements can interact with other elements to form
compounds. Hydrogen gas, for example, burns in oxygen
gas to form water.
Figure 1.10
Conversely, water can be decomposed into its component
elements (hydrogen and oxygen) by passing an electrical
current through it, as shown in Figure 1.7.
Figure 1.7 Water decomposes into its component elements, hydrogen and
oxygen, when a direct electrical current is passed through it. The volume of
hydrogen (on the right) is twice the volume of oxygen (on the left).
Pure water, regardless of its source, consists of 11% hydrogen and 89%
oxygen by mass.
This macroscopic composition corresponds to the molecular composition,
which consists of two hydrogen atoms combined with one oxygen atom.
As seen in Table 1.3, the properties of water bear no resemblance to the
properties of its component elements.
Hydrogen, oxygen, and water are each unique substances.
Law of constant composition: A law that states that the elemental
composition of a pure compound is always the same, regardless of its
source. This law is also known as law of definite proportions. It
was first put forth by the French chemist Joseph Louis Proust in 1800s.
Each of the followings can be classified as a heterogeneous mixture,
homogeneous mixture, compound, or element. How would you
classify each?
2) Ethyl alcohol
1) Iced tea
a) heterogeneous mixture
a) heterogeneous mixture
b) homogeneous mixture
b) homogeneous mixture
c) compound
c) compound
d) element
d) element
3)
a)
b)
c)
d)
Ozone
compound
homogeneous mixture
heterogeneous mixture
element
4)
a)
b)
c)
d)
Air in the classroom
heterogeneous mixture
homogeneous mixture
compound
element
5)
a)
b)
c)
d)
Table salt
heterogeneous mixture
homogeneous mixture
compound
element
1) b
2) c
3) a
4) b
1) Which of the following is not
matter?
a) elemental phosphorus
b) light
c) dust
d) pizza
6)
a)
b)
c)
d)
5) c
A salt and sand mixture
heterogeneous mixture
homogeneous mixture
compound
element
6) a
2) Which of the following is a
pure substance?
a) concrete
b) nitrogen
c) blue-cheese salad dressing
d) air
4)
a)
b)
c)
d)
Which of the following is not a state of matter?
Gas
Vacuum
Solid
Liquid
3) Passing an electric current through a certain substance produces
oxygen and sulfur. This substance cannot be a(n)
a) Compound
b) Element
c) Mixture
d) Pure substance
1) b
2) b
3) b
4) b
Three States of Matter
Matter can exist in one of three states of matter: a gas, a liquid, or a
solid.
A gas is highly
compressible and will
assume both the shape
and the volume of its
container.
A liquid is not
compressible and will
assume the shape but not
the volume of its
container.
A solid also is
not compressible,
and it has a fixed
volume and shape
of its own.
Some Characteristics of Gases, Liquids and Solids and the
Microscopic Explanation for the Behavior
gas
liquid
solid
assumes the shape
and volume of its
container
assumes the shape of
the part of the container
which it occupies
retains a fixed
volume and shape
particles can move past one
another
particles can move/slide past one
another
rigid - particles locked into
place
compressible
not easily compressible
not easily
compressible
lots of free space between
particles
little free space between particles
little free space between
particles
flows easily
flows easily
does not flow easily
particles can move past one
another
particles can move/slide past one
another
rigid - particles cannot
move/slide past one
another
Properties of Matter
Every substance has a unique set of properties (or characteristics) that
allow us to recognize it and to distinguish it from other substances. For
example, the properties listed in Table 1.3 allow us to distinguish hydrogen,
oxygen, and water from one another.
The properties of matter can be categorized as physical
properties or chemical properties.
Physical properties can be measured without changing the
identity and composition of the substance. These properties
include color, odor, density, melting point, boiling point, and
hardness.
Chemical properties describe the way a substance may
change or react to form other substances. A common chemical
property is flammability, the ability of a substance to burn in the
presence of oxygen.
Some properties—such as temperature, melting point,
and density—do not depend on the amount of the
sample (matter) being examined. These properties, called
intensive properties, are particularly useful in chemistry
because many can be used to identify substances.
Extensive properties of substances depend on the
quantity of the sample and include measurements of mass
and volume. Extensive properties relate to the amount of
substance present.
Physical or Chemical?
A physical change does not alter the composition
or identity of a substance.
sugar dissolving
ice melting
in water
A chemical change alters the composition or
identity of the substance(s) involved.
hydrogen gas burns in oxygen gas to form water
Which of the following is a chemical process?
a) dissolving sugar in water
b) crushing of stone
c) tarnishing of silver
d) melting of lead
Which of the following is an intensive quantity?
a) heat content of a substance
b) mass of a substance
c) density of a substance
d) volume of a substance
Which one of the following is a physical process?
a) the rusting of iron
b) the explosion of nitroglycerine
c) the baking of a potato
d) the condensation of water vapor
e) the formation of polyethylene from ethylene
c
c
d
Matter - anything that occupies space and has mass.
mass – measure of the quantity of matter
SI unit of mass is the kilogram (kg)
1 kg = 1000 g = 1 x 103 g
weight – force that gravity exerts on an object
weight = g x mass
on earth, g = 9.8 m/s2
on moon, g= 1.63 m/s2
A 60 kg bar will weigh
~600 N on earth
~100 N on moon
Table 1.2 SI Base Units
Base Quantity
Name of Unit
Length
meter
Mass
kilogram
Time
second
Current
ampere
Temperature
kelvin
Amount of substance
mole
Luminous intensity
candela
Symbol
m
kg
s
A
K
mol
cd
Table 1.3 Prefixes Used with SI Units
Prefix
Symbol
Meaning
Unit
Ex. meter
TeraGigaMegaKilo-
T
G
M
k
1012
109
106
103
DeciCentiMilli-
d
c
m
10-1
10-2
10-3
MicroNanoPico-
m
n
p
10-6
10-9
10-12
Volume – SI derived unit for volume is cubic meter (m3)
1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3
1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3
1 L = 1000 mL = 1000 cm3 = 1 dm3
1 mL = 1 cm3
Density – SI derived unit for density is kg/m3
1 g/cm3 = 1 g/mL = 1000 kg/m3
mass
density =
volume
m
d= V
A piece of platinum metal with a density of 21.5
g/cm3 has a volume of 4.49 cm3. What is its mass?
m
d= V
m = d x V = 21.5 g/cm3 x 4.49 cm3 = 96.5 g
K = 0C + 273.15
273 K = 0 0C
373 K = 100 0C
0F
= 9 x 0C + 32
5
32 0F = 0 0C
212 0F = 100 0C
0C
= 5 x (0F – 32)
9
0 0C = 32 0F
100 0C = 212 0F
Convert 172.9 0F to degrees Celsius.
9
=
x 0C + 32
5
0F – 32 = 9 x 0C
5
0F
5 x (0F – 32) = 0C
9
0C = 5 x (0F – 32)
9
0C = 5 x (172.9 – 32) = 78.3
9
Scientific Notation
The number of atoms in 12 g of carbon:
602,200,000,000,000,000,000,000
6.022 x 1023
The mass of a single carbon atom in grams:
0.0000000000000000000000199
1.99 x 10-23
N x 10n
N is a number
between 1 and 10
n is a positive or
negative integer
Scientific Notation
568.762
0.00000772
move decimal left
move decimal right
n>0
n<0
568.762 = 5.68762 x 102
0.00000772 = 7.72 x 10-6
Addition or Subtraction
1. Write each quantity with
the same exponent n
2. Combine N1 and N2
3. The exponent, n, remains
the same
4.31 x 104 + 3.9 x 103 =
4.31 x 104 + 0.39 x 104 =
4.70 x 104
Scientific Notation
Multiplication
1. Multiply N1 and N2
2. Add exponents n1 and n2
Division
1. Divide N1 and N2
2. Subtract exponents n1 and n2
(4.0 x 10-5) x (7.0 x 103) =
(4.0 x 7.0) x (10-5+3) =
28 x 10-2 =
2.8 x 10-1
8.5 x 104 ÷ 5.0 x 109 =
(8.5 ÷ 5.0) x 104-9 =
1.7 x 10-5
Significant Figures
• Any digit that is not zero is significant
1.234 kg
4 significant figures
• Zeros between nonzero digits are significant
606 m 3 significant figures
• Zeros to the left of the first nonzero digit are not significant
0.08 L 1 significant figure
• If a number is greater than 1, then all zeros to the right of
the decimal point are significant
2.0 mg
2 significant figures
• If a number is less than 1, then only the zeros that
are at the end and in the middle of the number are
significant
0.00420 g 3 significant figures
• When a number ends in zeros but contains no decimal point, the
zeros may or may not be significant. 5000 (one, two, three, or four
significant figures) 10,500 (three, four, or five significant figures)
The use of exponential notation eliminates the potential ambiguity of
whether the zeros at the end of a number are significant
1.03 x 104
Three significant figures
1.030 x 104
Four significant figures
1.0300 x 104
Five significant figures
How many significant figures are in
each of the following measurements?
24 mL
2 significant figures
3001 g
4 significant figures
0.0320 m3
3 significant figures
6.4 x 104 molecules
2 significant figures
560 kg
2 or 3 significant figures
560. kg
3 significant figures
Significant Figures
Addition or Subtraction
The answer cannot have more digits to the right of the decimal
point than any of the original numbers.
89.332
+ 1.1
90.432
3.70
-2.9133
0.7867
one significant figure after decimal point
round off to 90.4
two significant figures after decimal point
round off to 0.79
Significant Figures
Multiplication or Division
The number of significant figures in the result is set by the original
number that has the smallest number of significant figures
4.51 x 3.6666 = 16.536366
3 sig figs
round to
3 sig figs
6.8 ÷ 112.04 = 0.0606926
2 sig figs
= 16.5
round to
2 sig figs
= 0.061
Accuracy – how close a measurement is to the true value
Precision – how close a set of measurements are to each other
accurate
&
precise
precise
but
not accurate
not accurate
&
not precise
Dimensional Analysis
1. Determine which unit conversion factor(s) are needed
2. Carry units through calculation
3. If all units cancel except for the desired unit(s), then the
problem was solved correctly.
Desired unit
Given unit x
= Desired unit
Given unit
How many mL are in 1.63 L?
1 L = 1000 mL
1000 mL
1.63 L x
= 1630 mL
1L
2
1L
L
1.63 L x
= 0.001630
1000 mL
mL
We know that 1 inch is the same length as 2.54
centimeters. We’re told that the new start of the Indians
basketball team is 64 cm tall and that he’s going to be the
starting center. Based on height alone we’ll be able to tell if
he’ll help the team but we Americans think in INCHES not
CENTIMETERS so we need to convert units.
Desired unit
Remember
Given unit x
= Desired unit
Given unit
Desired unit
64 cm X
Given unit
1 in
2.54 cm
64
2.54
in
= 25.4 in
The speed of sound in air is about 343 m/s. What is
this speed in miles per hour?
meters to miles
seconds to hours
1 mi = 1609 m
1 min = 60 s
1 mi
60 s
m
x
x
343
s 1609 m
1 min
1 hour = 60 min
60 min
mi
x
= 767
hour
1 hour
Conversion factors
A car travels 28 mi per gallon of gasoline. How many
kilometer per liter will it go?
1.0 km = 0.62137 mi or
0.62137 mi
1.0 km
or
3.7854 L
1.0 gal
1.0 gal = 3.7854 L
or
or
1.0 km
0.62137 mi
1.0 gal
3.7854 L
TWO steps
mi
28
gal
1.0 km
x
0.62137 mi
1 gal
km
45 gal x
3.7854 L
km
= 45 gal
= 12
km
L
Step 1
Step 2
ONE step
mi
28
gal
1 km
1 gal
x
x
0.62137 mi
3.7854 L
= 12
km
L
Watch for significant figures. The real number is 11.9 km/L, however, here
we have three sig. figures. We have started with a two sig. figure number
(28). Thus, the final answer has to have two significant figures!