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Chapter 1
Chapter 1
Chapter 1
Elemental Molecules
Some elemental substances are found in nature
as diatomic molecules:
H2, N2, O2, F2, Cl2, Br2, I2 , P4 , S8
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Chapter 1
Chemical Changes…chemical reactions we …
When writing a chemical equation we use
formulas to represent the pure substances
that appear as reactants and products.
2Mg(s) + CO2(g) → 2MgO(s) + C(s)
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
2Al(s) + Fe2O3(s) → Al2O3(s) + 2Fe(s)
2Al(s) + 3Br2(g) → 2AlBr3(s)
Chapter 1
Chemistry is a quantitative science which
depends on exact measurements. In fact, it
was because of careful measurements of
reactants and products in chemical reactions
that the very nature of chemistry was
explained. Because of exact measurements
early chemists were able to determine
formulas, write equations for reactions before
there was any realistic concept of nature and
model for the structure of the atom.
Chapter 1
Quantitative Measurements
Consist of two parts…
3.416 g
15.5 mL
5.0 km
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Chapter 1
Two dominant measurement systems
English and metric
Fundamental Quantitative
Units
Quantity
Mass
Length
Time
Temperature
Amount
Electrical Current
Luminous Intensity
Unit
kilogram
meter
second
Kelvin
mole
ampere
candela
Metric Prefixes Exponential Prefix Symbol Meaning tera
T
1,000,000,000,000
giga
G
1,000,000,000
mega
M 1,000,000 kilo
k
1,000 hecto
h
100
deka
da 10
deci
d
0.1
centi
c 0.01 milli
m 0.001 micro
µ
0.000001 nano
n 0.000000001
pico
p 0.000000000001
Abbrev
kg
m
s
K
mol
A
cd
Notation
1012
109 106 103 102 101 10–1 10–2 10–3 10–6 10–9 10–12 3
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Metric Prefixes Prefix Symbol Meaning tera
T
1,000,000,000,000
giga
G
1,000,000,000
mega M
1,000,000 kilo
k
1,000 hecto
h
100
deka
da 10
deci
d
0.1
How many grams in 11.3 gigagrams?
Exponential Notation 1012 109 106 103 102 101 10–1 Metric Prefixes Prefix Symbol Meaning tera
T
1,000,000,000,000
giga
G
1,000,000,000
mega
M 1,000,000 kilo
k
1,000 hecto
h
100
deka
da 10
deci
d
0.1
How many grams in 11.3 gigagrams?
11.3 Gg (1 x 109 g /1 Gg) = 1.13 x 1010 g
Exponential Notation 1012 109 106 103 102 101 10–1 Metric Prefixes Exponential Prefix Symbol Meaning Notation
kilo
k
1,000 103 hecto
h
100
102 deka
da 10
101 deci
d
0.1
10–1 centi
c
0.01 10–2 milli
m
0.001 10–3 micro
µ
0.000001 10–6 nano
n
0.000000001
10–9 How many nanograms in 0.0753 kilograms?
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Metric Prefixes Exponential Prefix Symbol Meaning Notation kilo
k
1,000 103 hecto
h
100
102 deka
da 10
101 deci
d
0.1
10–1 centi
c
0.01 10–2 milli
m
0.001 10–3 micro
µ
0.000001 10–6 nano
n
0.000000001
10–9 How many nanograms in 0.0753 kilograms?
0.0753 kg (1000 g/1 kg) (1 ng/1 x 10-9 g) = 7.53 x 1010 ng
Physical
Quantity
Measured
Volume
Unit
Name
liter
Unit
Symbol
L Definition
1000 cm3 or 1 dm3
Temperature Celsius ˚C ˚C = K – 273.16 Temperature Fahrenheit ˚F ˚F = 9/5˚C + 32 Heat joule J The work performed
by a force of 1 newton
acting through a distance of 1 meter
Pressure
Pascal Pa
The force of 1
newton acting on an area of 1 m2 Density
g/cm3
The mass of 1 cm3
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Significant Figures
1.  All non zero digits are significant;
2.  Reading from left to right begin counting with the
first nonzero digit. Zeros that precede the first
nonzero digit are not significant.
3.  Zeros are significant when they appear; in the
middle of a number, at the end of a number that
includes a decimal point.
4.  Zeros at the end of a number without a decimal
point are ambiguous. We will assume they are
NOT significant.
Rounding
Look at the left most digit to be dropped
1.  If this digit is greater than '5', or is '5' followed by
nonzero digits, add '1' to the last digit to be
retained and drop all the digits further to the
right. 2.  If this digit is less than '5', drop it and all digits
further to the right.
Using Significant Figures"
"
1.  When adding or subtracting measured quantities,
there should be the same number of decimal places
in the answer as there are in the measurement with
the least number of decimal places."
"
2. "When multiplying and dividing measured quantities,
there should be as many significant figures in the
answer as there are in the measurement with the
least number of significant figures."
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Conversions
•  1 meter = 100 centimeters
The unit conversion factor for this definition is;
Either can be used. Given the number of
centimeters the first unit conversion factor can be
used to convert centimeters to meters. Given the
number of meters the second unit conversion factor
can be used to convert meters to centimeters. 7