Chemistry: A Molecular Approach,
3rd edition. NJ Tro
Chapter 1: Matter, Measurement,
and Problem Solving
1
Chemistry: An Overview
Chemistry: The central science
a)  Is the foundation for many other disciplines:
biology, geology, pharmacy, medicine
b)  Connects other sciences such as:
materials science, nanotechnology, environmental
science, …
What is matter made of?
Matter -- anything that occupies space and has
mass (the macroscopic world)
Today we are fairly sure that matter consists of
individual atoms (the microscopic world)
2
To truly understand chemistry you must learn to think on the
atomic level: Start With The Periodic Table of the Elements
1
18
IUPAC Periodic Table of the Elements
1
H
2
He
helium
hydrogen
[1.007; 1.009]
2
3
4
Li
Be
lithium
beryllium
[6.938; 6.997]
9.012
11
13
14
15
16
17
atomic number
5
6
7
8
9
10
Symbol
B
C
N
O
F
Ne
Key:
4.003
boron
carbon
nitrogen
oxygen
fluorine
neon
[10.80; 10.83]
[12.00; 12.02]
[14.00; 14.01]
[15.99; 16.00]
19.00
20.18
12
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
sodium
magnesium
4
5
6
7
8
9
10
11
12
silicon
phosphorus
sulfur
chlorine
argon
24.31
3
aluminium
22.99
26.98
[28.08; 28.09]
30.97
[32.05; 32.08]
[35.44; 35.46]
39.95
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
potassium
calcium
scandium
titanium
vanadium
chromium
manganese
iron
cobalt
nickel
copper
zinc
gallium
germanium
arsenic
selenium
bromine
krypton
39.10
40.08
44.96
47.87
50.94
52.00
54.94
55.85
58.93
58.69
63.55
65.38(2)
69.72
72.63
74.92
78.96(3)
79.90
83.80
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
technetium
ruthenium
rhodium
palladium
silver
cadmium
indium
tin
antimony
tellurium
iodine
xenon
101.1
102.9
106.4
107.9
112.4
114.8
118.7
121.8
127.6
126.9
131.3
name
standard atomic weight
rubidium
strontium
yttrium
zirconium
niobium
molybdenum
85.47
87.62
88.91
91.22
92.91
95.96(2)
55
56
57-71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs
Ba
lanthanoids
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
caesium
barium
hafnium
tantalum
tungsten
rhenium
osmium
iridium
platinum
gold
mercury
thallium
lead
bismuth
polonium
astatine
radon
132.9
137.3
178.5
180.9
183.8
186.2
190.2
192.2
195.1
197.0
200.6
[204.3; 204.4]
207.2
209.0
87
88
89-103
104
105
106
107
108
109
110
111
112
114
116
Fr
Ra
actinoids
Rf
Db
Sg
Bh
Hs
Mt
Ds
Rg
Cn
Fl
Lv
francium
radium
rutherfordium
dubnium
seaborgium
bohrium
hassium
meitnerium
darmstadtium
roentgenium
copernicium
flerovium
livermorium
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
La
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
lanthanum
cerium
praseodymium
neodymium
promethium
samarium
europium
gadolinium
terbium
dysprosium
holmium
erbium
thulium
ytterbium
lutetium
138.9
140.1
140.9
144.2
150.4
152.0
157.3
158.9
162.5
164.9
167.3
168.9
173.1
175.0
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
Ac
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
actinium
thorium
protactinium
uranium
neptunium
plutonium
americium
curium
berkelium
californium
einsteinium
fermium
mendelevium
nobelium
lawrencium
232.0
231.0
238.0
Notes
- IUPAC 2009 Standard atomic weights abridged to four significant digits (Table 4 published in Pure Appl. Chem. 83, 359-396 (2011);
doi:10.1351/PAC-REP-10-09-14). The uncertainty in the last digit of the standard atomic weight value is listed in parentheses following the value.
In the absence of parentheses, the uncertainty is one in that last digit. An interval in square brackets provides the lower and upper bounds of the
standard atomic weight for that element. No values are listed for elements which lack isotopes with a characteristic isotopic abundance in natural
terrestrial samples. See PAC for more details.
INTERNATIONAL UNION OF
PURE AND APPLIED CHEMISTRY
- “Aluminum” and “cesium” are commonly used alternative spellings for “aluminium” and “caesium.”
- Claims for the discovery of all the remaining elements in the last row of the Table, namely elements with atomic numbers 113, 115, 117 and 118,
and for which no assignments have yet been made, are being considered by a IUPAC and IUPAP Joint Working Party.
For updates to this table, see iupac.org/reports/periodic_table/. This version is dated 1 June 2012.
Copyright © 2012 IUPAC, the International Union of Pure and Applied Chemistry.
3
1.2 The Scientific Approach to Knowledge
Hypothesis: a tentative interpretation or explanation of the observations
- tested by experiments
Experiments: controlled procedures designed to generate observations
Scientific Law: a brief statement that summarizes past observations and
predicts future ones
Theory: a model that explains why nature is the way it is
4
Two Fundamental Concepts of Chemistry
1.  Matter is composed of various types of atoms:
•
Atoms make up molecules
2.  One substance changes to another by reorganizing
the way the atoms are attached to one another:
•
A chemical change -- chemistry
CH4 + 2O2 à CO2 + 2H2O
H2 + O2 à H2O2
H2O à H2 + O
2H2(g) + O2(g) à 2H2O(l)
“Chemistry”
5
1.3 The Classification of Matter: 3 states of matter:
H2O(s)
!
H2O(l)
!
H2O(g)
A Physical Change is not Chemistry
6
1.3 The Classification of Matter: (Polymorphism)
7
1.3 The Classification of Matter according to Composition: Elements,
Compounds, and Mixtures
8
1.4 Physical and Chemical Changes/Properties
Physical Changes do not alter
the composition of matter.
Chemical Changes alter the
composition of matter.
A Physical Property is one
that a substance displays
without changing its
composition.
A Chemical Property is one
that a substance displays
only by changing its
composition via a chemical
change.
9
1.4 Physical and Chemical Changes/Properties
Any sort of “Rusting” is a
Chemical Change. The
composition of matter is altered.
10
1.5 Energy and Physical and Chemical Changes:
Energy: The capacity to do work(w) or produce heat(q)
1)  Energy is always conserved in a chemical or physical change
2)  Systems with high potential energy tend to change in a direction
of lower potential energy, releasing energy into the surroundings
11
1.6 The Units of Measurement I: SI units
A quantitative observation (measurement) consists of 2 parts:
1. A number
Both must be present for a
2. A unit
measurement to be meaningful!
The system of units we are going to use is based on the metric system:
~ 2.2 lb.
~1.1 yards
~6x1023 particles
12
1999 Mars Climate Orbiter: $125,000,000 lost.
“The root cause of the loss was a failed translation of
English units into metric units.”
13
1.6 Units of Measurement II: prefixes
Because the fundamental units are not always convenient,
prefixes are used to change the size of the unit:
14
1.8 Solving Chemical Problems:
convert from one system of units to another:
15
1.8 Dimensional Analysis I: or the unit factor method
convert from one system of units to another:
Example 1: convert 12 inches to cm
By definition (Back cover of book): 1 inch = 2.54 cm, exactly
1. divide by 2.54 cm:
2.54 cm = 1 in.
2.54 cm
2.54 cm
= 1 =
2. divide by 1 in.:
2.54 cm = 1 in.
1 in.
1 in.
unit factors
12 inches
2.54 cm
1 inch
= 30.5 cm
16
1.8 Solving Chemical Problems: Temperature
3 major T scales, definition & conversion
Tk and Tc differ in zero point
Tk = Tc + 273.15
Tc = Tk - 273.15
TF differs from Tk and Tc in
zero point and degree size
TF = 32 + (Tc x 9/5)
Tc = 5/9(TF - 32)
17
1.8 Temperature II; normal body & room temperatures
Tc = 5/9(TF - 32)
RT: 68 oF = xx oC ?
Tc = 5/9(68 - 32) = 20 oC
18
1.8 Density, a Derived Unit: mass per unit volume
mass
density =
=d
volume
or
ρ
- a physical
property often
used to
identify a
substance
19
1.8 Density II:
Q. A chemist finds that 25.00 cm3 of a substance has
a mass of 19.625 g at 25oC. Which of the following
compounds is most likely the substance?
density = m/V
19.625 g
3
=
0.7850
g/cm
25.00 cm3
compound
Chloroform
Diethyl ether
ethanol
Isopropyl
alcohol
density(g/cm3)
1.492
0.714
0.789
0.785
toluene
0.867
20
1.8 Density III:
Q. instead of 19.625 g the chemist rounded to 20 g.
Which compounds is most likely the substance?
density = m/V
20 g
3
=
0.8
g/cm
25.00 cm3
compound
Chloroform
Diethyl ether
ethanol
Isopropyl
alcohol
density(g/cm3)
1.492
0.714
0.789
0.785
toluene
0.867
*These calculations bring up a important point about
significant figures and uncertainty in measurements …21
1.7 The Reliability (Uncertainty) of a Measurement I:
1.  A measurement always has a degree of uncertainty:
2.  The uncertainty depends on the precision of the measuring
device
3.  The way we indicate the uncertainty
in a measurement is by recording
the number of certain digits plus the
first uncertain digit
(the estimated number)
•  These numbers are called:
significant figures
V1 = 2.81 mL
V2 = 0.280 mL
22
1.7 Uncertainty in Measurements II: accuracy and precision
1.  Accuracy: the agreement of a particular value with the true
value
2.  Precision: the degree of agreement among several
measurements of the same quantity
(the reproducibility)
True values:
2.80 mL
V1 = 2.81 mL
0.300 mL
V2 = 0.280 mL
23
24
1.7 Significant Figures and Calculations I: counting
A) Nonzero integers always count as significant figures
1234 has 4 sig figs
B) Three types of zeroes:
1.  Leading zeros do not count as significant figures
0.089 has 2 sig figs
2.  Captive zeros always count as significant figures
12.03 has 4 sig figs,
3.  Trailing zeros are significant only if the number contains a
decimal point
2.4000 has 5 sig figs, 2400 has 2 sig figs
C) Exact numbers have an infinite number of significant
figures
1 inch = 2.54 cm, exactly, 5 experiments, π
25
1.7 Significant Figures II: mathematical operations
A) multiplication and division: number of sig figs in result is the
same as the least precise measurement in calculation
1. x 2.00 = 2 1 sig figs
B) addition and subtraction: the result has the same number of
decimal places as the least precise measurement used in
the calculation
12.013
+18.1
30.113 => 30.1, 1 decimal digit
C) rules for rounding: in a series of calculations round at the
end; if the digit to be removed is less than 5 the preceding
digit stays the same, if the digit to be removed is greater
than 5 the preceding digit is increased by 1:
1.331 rounded to 2 sig figs is 1.3
26
1.36 rounded to 2 sig figs is 1.4