Chemical Foundations
Chapter 1
Chemistry
Chemistry deals with situations in which the
nature of a substance is changed by altering
its composition so that entirely new
substances are synthesized or particular
properties of existing substances are
enhanced.
Science
Science is both a noun and a verb.
Science is a body of knowledge and a
method of adding to that body of
knowledge.
Steps in the Scientific Method
1. Observations
quantitative - measurement involves a
number and a unit.
qualitative
2. Formulating hypotheses
possible explanation for the observation
3. Performing experiments
gathering new information to decide
whether the hypothesis is valid
Outcomes Over the Long-Term
Theory (Model)
- A set of tested hypotheses that give an
overall explanation of some natural
phenomenon.
Natural Law
The same observation applies to many
different systems
Example - Law of Conservation of
Mass
Law vs. Theory
A law summarizes what happens;
a theory (model) is an attempt to
explain why it happens.
01_03
Observation
Hypothesis
Experiment
Theory
(model)
Theory
modified
as needed
Law
Prediction
Experiment
The various parts of the scientific method.
Problems of the Scientific
Method
Scientists must be objective when using the
scientific method. The scientific method is
affected by:
profit motives
religious beliefs
wars
misinterpretation of data
budgets
emotions
fads
prejudices
politics
peer pressure
Nature of Measurement
Measurement - quantitative observation consisting
of 2 parts
Part 1 - number
Part 2 - scale (unit)
Examples:
20 grams
6.63   Joule seconds
International System
(le Système International)
Based on metric system and units
derived from metric system.
The Fundamental SI Units
Physical Quantity
Name
Abbreviation
kilogram
kg
Length
meter
m
Time
second
s
Temperature
Kelvin
K
Electric Current
Ampere
A
mole
mol
candela
cd
Mass
Amount of Substance
Luminous Intensity
01_05
1m3
1dm3= 1 L
1cm3= 1 mL
1 cm
1 cm
One liter is defined as a cubic decimeter and 1 mL is one
cubic centimeter.
01_06
mL
100
90
80
70
60
50
40
30
20
10
mL
0
1
2
3
4
Calibration mark
indicates 25-mL
volume
100-mL graduated
cylinder
Valve (stopcock)
controls the liquid
flow
25-mL pipet
Calibration mark
indicates 250-mL
volume
45
46
47
48
49
50
50-mL buret
250-mL volumetric flask
Common types of laboratory equipment used to measure
liquid volume.
Mass & Weight
Mass is a measure of the resistance of an
object to a change in its state of motion -- a
constant.
Weight is the measure of the pull of gravity on
an object and varies with the object’s
location.
Uncertainty in Measurement
A digit that must be estimated is
called uncertain. A measurement
always has some degree of
uncertainty.
Buret
01_08
mL
0
10
22.2 mL
20
30
40
50
Measurement of volume using a buret. The volume is read
at the bottom of the meniscus.
Precision and Accuracy
Accuracy refers to the agreement of a
particular value with the true value.
Precision refers to the degree of
agreement among several elements of
the same quantity.
01_09
(a)
(b)
(c)
a) is neither precise nor accurate, b) is precise but not
accurate (small random, large systematic errors) c) both
precise and accurate (small random, no systematic errors.
Types of Error
Random Error (Indeterminate Error) measurement has an equal probability of
being high or low.
Systematic Error (Determinate Error) Occurs in the same direction each time
(high or low), often resulting from poor
technique.
Accuracy
Sample Exercise 1.2 on page 13.
Trial
Graduated Cylinder
1
25 mL
2
25 mL
3
25 mL
4
25 mL
5
25 mL
Average
25 mL
Which is more accurate?
Buret
Buret
26.54 mL
26.51 mL
26.60 mL
26.49 mL
26.57 mL
26.54 mL
Graduated cylinder produces systematic error --value is
too low.
Exponential Notation
Also called scientific notation and powers of
ten notation. Exponential notation has two
advantages:
the number of significant digits can easily be
indicated
fewer zeros are needed to write a very large or
very small number.
Rules for Counting Significant
Figures - Overview
1. Nonzero integers
2. Zeros
leading zeros
captive zeros
trailing zeros
3. Exact numbers
Rules for Counting Significant
Figures - Details
Nonzero integers always count as
significant figures.
3456 has
4 sig figs.
Rules for Counting Significant
Figures - Details
Zeros
- Leading zeros do not count as
significant figures.
0.0486 has
3 sig figs.
Rules for Counting Significant
Figures - Details
Zeros
-
Captive zeros always count as
significant figures.
16.07 has
4 sig figs.
Rules for Counting Significant
Figures - Details
Zeros
-
Trailing zeros are significant
only
if the number contains a decimal
point.
9.300 has
4 sig figs.
Rules for Counting Significant
Figures - Details
Exact numbers have an infinite number
of significant figures. Can come from
counting or definition.
15 atoms
1 inch = 2.54 cm, exactly
Rules for Significant Figures in
Mathematical Operations
Multiplication and Division: # sig figs
in the result equals the number in the
least precise measurement used in the
calculation.
6.38  2.0 =
12.76  13 (2 sig figs)
Rules for Significant Figures in
Mathematical Operations
Addition and Subtraction: # sig figs in
the result equals the number of decimal
places in the least precise measurement.
6.8 + 11.934 =
18.734  18.7 (3 sig figs)
Rules for Rounding
1. In a series of calculations, carry the extra
digits through to the final result, then round.
2. If the digit to be removed
a. is less than five, the preceding digit stays
the same.
b. is equal to or greater than five, the
preceding digit is increased by 1.
Dimensional Analysis
Also called unit cancellation is a method of
solving problems by using unit factors to
change from one unit to another.
Unit factor -- the unit that you have goes on
bottom, and the unit that you want goes on
top.
Dimensional Analysis
Proper use of “unit factors” leads to proper
units in your answer.
OK:
NOT OK:
1 kilometer
0.62137 mile

0.62137 mile
1 kilometer
1 kilometer
1 mile

0.62137 mile
0.62137 kilometer
Dimensional Analysis
What is the dimension of a 25.5 in bicycle
frame in centimeters?
(25.5 in)(2.54 cm/1 in) = 64.8 cm
Units must be cancelled and the answer must
have correct sig figs, be underlined, and
include proper units!!
Temperature
Celsius scale = C
Kelvin scale = K
Fahrenheit scale = F
01_10
Fahrenheit
Boiling
point
of water
212F
Kelvin
100C
100
Celsius
degrees
180
Fahrenheit
degrees
Freezing
point
of water
Celsius
373.15 K
100
kelvins
32F
0C
273.15 K
-40F
-40C
233.15 K
Three major temperature scales.
Temperature
K  C  27315
.
C
F - 32

100
180
Temperature Calculations
Convert - 40.0 oC to Kelvin.
K = C + 273.15
K = -40.0 + 273.15
K = 233.2 K
Temperature Calculations
Convert - 40.0 oC to Fahrenheit.
C
F - 32

100
180
-40.0
F - 32

100
180
100 F - 3200 = -7200
100 F = -4000
F = - 40.0 oF
Density
Density is the mass of substance per unit
volume of the substance:
mass
density =
volume
m
D
V
Density Calculations
If an object has a density of 0.7850 g/cm3 and
a mass of 19.625 g, what is its volume?
m
D
V
m
V
D
19.625 g
V
g
0.7850
cm 3
V = 25.00 cm3
Matter: Anything
occupying space and
having mass.
Classification of Matter
Three States of Matter:
Solid: rigid - fixed volume and shape
Liquid: definite volume but assumes
the shape of its container
Gas: no fixed volume or shape assumes the shape of its container
Types of Mixtures
Mixtures have variable composition.
A homogeneous mixture is a solution
(for example, vinegar)
A heterogeneous mixture is, to the
naked eye, clearly not uniform (for
example, a bottle of ranch dressing)
HOMOGENEOUS MATTER
- a substance with the same properties
throughout -- a pure substance.
Elements and compounds are pure substances
(homogeneous matter).
HETEROGENEOUS MATTER
- has different properties throughout -- a
mixture.
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Salt and pepper
soil
granite
sea water
spaghetti & meat balls
SEPARATION OF MIXTURES
- mixtures can be separated into pure
substances by physical means.
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distillation
filtration
centrifuging
magnet
evaporation
chromatography
01_13
Thermometer
Condenser
Vapors
Distilling
flask
Water out
Cool
water in
Receiving
flask
Burner
Distillate
Simple laboratory distillation apparatus.
CENTRIFUGE
Paper Chromatography
Chromatography has two phases of matter: a stationary
phase (the paper) and a mobile phase ( the liquid).
Compounds & Elements
Compound: A substance with a
constant composition that can be
broken down into elements by
chemical processes.
Element: A substance that cannot
be decomposed into simpler
substances by chemical means.
Universe
Matter
Energy
Physical
Change
Homogeneous
Heterogeneous
Solution
Pure Substance
Potential
Energy
Mixture
Position
Element
Chemical
Change
Electron Levels
Electrons
Kinetic
Energy
Composition
Compound
Gravitational
Nucleus
Protons
Neutrons
Electrostatic
“TO BUILD FROM MATTER
IS SUBLIMELY GREAT,
BUT GODS AND POETS
ONLY CAN CREATE.”
Pitt