Daniel L. Reger
Scott R. Goode
David W. Ball
www.cengage.com/chemistry/reger
Chapter 1
Introduction to Chemistry
What is Science?
“Natural abilities are like natural plants; they
need pruning by study.” – Sir Francis Bacon
(1561-1626)
The Nature of Science and Chemistry
• Definitions
• Science: knowledge
• Sir Francis Bacon: “And thus knowledge itself is
power”
• Modern science, the acquisition of knowledge,
is acquired by experience (experiment)
• Chemistry: the study of matter and its
interactions with other matter and with
energy.
Chemistry and the Natural Sciences
The Scientific Method
Scientific method: investigations
that are guided by theory and earlier
experiments.
• Hypothesis: a possible explanation
for an event.
• Law: a statement that summarizes a
large number of observations.
• Theory: an explanation of the laws of
nature.
•
Matter
Matter: anything that has mass and
occupies space.
• Mass: the quantity of matter in an object.
• Weight: the force of attraction between
an object and other objects.
•
Mass and Weight
Mass on
moon and
earth is the
same.
Weight on
moon and
earth is the
different.
Properties of Matter
Property: anything observed or
measured about a sample of matter.
• Extensive property: depends on the
size of the sample.
•
•
•
mass, volume
Intensive property: independent of
sample size.
•
density, color, melting or boiling point
Physical Properties and Changes
•
Physical properties: can be measured
without changing the composition of the
sample.
•
•
mass, density, color, melting point
Physical change: a change that occurs
without changing the composition of the
material.
•
freezing, melting
Chemical Properties
•
Chemical properties: describe the
reactivity of a material.
•
•
Natural gas burns in air; iron rusts.
Chemical change: at least part of the
material is changed into a different kind
of matter.
•
The digestion of sugar is a chemical
change.
Practice
State if the underlined property or changes is intensive or
extensive and chemical or physical.
a)
b)
c)
d)
e)
The color of mercury is silvery.
The sample of iron rusts by reaction with oxygen.
The heat released by burning coal can power a city.
Water boils at 100°C.
A new pencil is 10 inches long.
Classification of Matter
• Substances - a material that is
chemically the same throughout.
• Two types of substances
• Elements cannot be broken into simpler
substances.
• Compounds can be broken down into
elements.
Substances
•
•
•
Substance: cannot be separated into
component parts by physical methods.
Compound: a substance which can be
separated into simpler substances by
chemical methods.
Element: a substance which cannot be
separated into simpler substances by
chemical methods.
Mixtures
•
Mixture: matter that can be separated into
simpler materials by physical methods.
•
•
•
Heterogeneous mixture: composition of the
mixture changes from one part to another.
Homogeneous mixture or solution:
composition of the mixture is uniform
throughout.
Alloy: a solution of a metal and another
material (usually another metal).
Classification of Matter
Practice
Identify the following types of matter as elements,
compounds, heterogeneous mixtures, or
homogeneous mixtures.
a)
b)
c)
d)
Sodium chloride
Stainless steel
Chlorine
soil
Measurement
• Most modern science depends on
measurements
• Parts of a measurement
• The object of the measurement
• The value of the measurement
• The units of the measurement
• The reliability of the measurement
• Example “The mass of iron was 4.0501 grams
• All parts MUST be present in an answer
for complete credit!!
Accuracy and Precision
•
Modern chemistry is largely based on
experimental measurements. The
confidence in measurements involves:
•
•
Accuracy: agreement of a measurement
with the true value.
Precision: agreement among repeated
measurements of the same quantity.
Accuracy and Precision
accurate
and
precise
accurate
but not
precise
precise
but not
accurate
neither
accurate
nor precise
Accuracy and Precision
Significant Figures
•
The number of significant figures is
the number of digits from the first nonzero digit through the last reported digit.
•
•
•
The uncertainty is at least ±1 unit in the last
reported digit.
Leading zeros – zeros preceding the first
non-zero digit are NEVER significant.
Trailing zeros – a decimal point is the key.
•
•
No decimal – trailing zeros are NOT significant
Decimal – trailing zeros ARE significant
Significant Figures
•
Quantities that are not limited by
significant figures:
•
•
•
counted numbers or tallies.
defined numbers.
the power of ten in exponential notation.
Significant Figures
How many significant figures are
present in each of the measured
quantities?
• 0.0012
106
2006
900.0
1.0012
0.001060
•
Significant Figures
Since trailing zeros in numbers without a
decimal points may be confusing for
significant figures use scientific
notation.
• 100
1? Or should there have been a decimal?
1 x 102
1
2
1.0 x 10
2
2
1.00 x 10
3
•
Practice
•Determine
the number of significant figures:
100.
100.0
30505
437,000
-3
125,904,000
4.80 x 10
-3
4.800 x 10
0.0048
Uncertainty in Addition and Subtraction
The absolute uncertainty can be no
smaller than the least accurate number.
•
12.02
- 10.4
1.62
•
1.6
• The answer should have no more
decimal places than the least accurate
number.
•
Uncertainty in Multiplication and Division
•
•
Answers should have no more significant
figures than the least accurate number.
3121 x 12 = 37452 = 3.7 x 10
# sig. digits 4
x 2 = 2
= 2
4
NOT 37!!!!!!
37000 is questionable
Mixed Operations
•
Determine accuracy in the same order as
the mathematical operations, # of
significant digits are in red.
m
3
2.79 g
3
2.79 g
=
8.34 mL - 7.58 mL 0.76mL
v
2
3
3
• density = 3.7 g/mL 2
•
=
Be mindful of what your calculator gives you!!
Rounding
• Be cautious about rounding during
multiple steps.
• Keep more significant figures than you
need in intermediate steps.
• Ex:
• 2.5 x 4.50 x 11.25 = ?
Practice
•
Evaluate each expression to the correct
number of significant figures.
(a) 4.184 x 100.620 x (25.27 - 24.16)
(b)
(c)
8.925 - 8.904
x 100%
8.925
9.6 x 100.65
+ 4.026
8.321
Practice
Calculate each to the correct number
of significant figures .
a) 0.1654 + 2.07 - 2.114
b) 8.27 x (4.987 - 4.962)
c)
d)
9.5 + 4.1 + 2.8 + 3.175
4
9.025 - 9.024
9.025
(4 is exact)
x 100%
Base Units in the SI
Quantity
Unit
Abbreviation
Length
meter
m
Mass
kilogram kg
Time
second
s
Temperature
kelvin
K
Amount
mole
mol
Electric current
ampere
A
Luminous intensity candela
cd
Common Prefixes Used With SI Units
Prefix
megakilocentimillimicronanopico-
Abbreviation Meaning
6
M
10
3
k
10
-2
c
10
-3
m
10
-6
m
10
-9
n
10
-12
p
10
Prefixes Used With SI Units
1 kilogram
is
equal
to
1000 g.
Unit Conversion Factors
Unit conversion factor: a fraction in
which the numerator is a quantity equal or
equivalent to the quantity in the
denominator, but expressed in different
units
• The relationship 1 kg = 1000 g
• Generates two unit conversion factors:
 1kg 
 1000 g 

 and 

 1000 g 
 1kg 
•
Unit Conversions
• Lets convert 5.73 g to kg.
• Start with what you know!!!
• Add conversion factors to cancel units
• Units must be same on top & bottom to cancel
 1kg 
 
5.73g  
 1000g 
grams on top
0.00573 kg
grams on bottom
Practice
Convert the following:
a) 17.43 km to cm
b) 165 μg to kg
Conversion Among Derived Units
•
•
•
Volume is the product of three lengths.
The standard unit of volume is the cubic
meter (m3).
100 cm = 1 m
(100 cm)3 = (1 m)3
6
3
3
10 cm = 1 m
Two important non-SI units of volume are
the liter and milliliter.
3
1 liter (L) = 1000 mL = 1000 cm
1 mL = 1 cm3
Volume
Volumes
can be
expressed
in different
units
depending
on the size
of the
object.
1 m3
contains
1000 L
1L
contains
1000 mL
Using Unit Conversions
•
Express a volume of 1.250 L in mL,
3
3
cm , and m
1000 mL 

1.250 L  
  1,250 mL
 1L 
 1000 cm3 
3


1.250 L  
 1,250 cm

 1L

 1 m3 
-3 3
  1,250  10 m
1.250 L   6
3
 10 cm 
Density
•
•
Density: mass per unit volume
m
d 
V
3
Density, in SI base units, is kg/m
-3
(kg m ).
• Most commonly used density units are
-3
3
g/cm (g cm or g/mL) for solids and
liquids, and g/L for gases.
•
Conversions Between Equivalent Units
3
The density of Ti is 4.50 g/cm or
3
4.50 g = 1 cm .
• Calculate the volume of 7.20 g Ti.
•
What we know
Answer:
 1 cm3 
3


7.20 g Ti  
 1.60 cm Ti

 4.50 g 
Units cancel
√ number
√ units
√ object
√ sig figs
English System
Practice
a) Express 323 milliliters in gallons.
b) Express 3.61 cubic feet in cubic centimeters.
Temperature Conversion Factors
 1.8o F 
TF  TC   o   32o F
 1.0 C 
o

1.0
C
o

TC  TF  32 F  
o 
 1.8 F 
TK  TC  273.15


For water
0
Kelvin
-273o Celsius
-460o Fahrenheit
273
0o
32o
373
100o
212o
Practice
•
Express 17.5°C in °F and in K.
Practice
• It has been estimated that 1.0 g of seawater contains 4.0 pg
of Au. The total mass of seawater in the oceans is 1.6x1012
Tg, If all of the gold in the oceans were extracted and spread
evenly across the state of Georgia, which has a land area of
58,910 mile2, how tall, in feet, would the pile of Au be?
Density of Au is 19.3 g/cm3. 1.0 Tg = 1012g.
Practice
• One metal object is a cube with edges of 3.00 cm and a mass
of 140.4 g. A second metal object is a sphere with radius
1.42 cm and a mass of 61.6 g. Are these objects made of the
same or different metals? Assume the calculated densities
are accurate to 1.00%.
Practice
A 40-lb container of peat moss measures 14 x 20 x 30
in. A 40-lb container of topsoil has a volume fo 1.9 gal.
• Calculate the density of both the peat moss and the
topsoil.
• How many bags of peat moss are needed to cover
an area measuring 10 ft x 20 ft x 2 in?
Practice
On a typical day, a hurricane expends the energy equivalent
to the explosion of two thermonuclear weapons. A
thermonuclear weapon has the explosive power of 1.0 Mton
of nitroglycerin. Nitroglycerin generates 7.3 kJ of explosive
power per gram of nitroglycerin. The hurricane’s energy
comes from the evaporation of water that requires 2.3 kJ per
gram of water evaporated. How many gallons of water does
a hurricane evaporate per day?
THINK!!
Homework:
OWL: All of the required assignments
book: All questions from the end of the chapter are
recommended as practice.