Chemical
Foundations
ZUMDAHL CHAPTER 1
What is chemistry?
According to the Oxford Dictionary…
“The branch of science concerned with the substances of which matter
is composed, the investigation of their properties and reactions, and the
use of such reactions to form new substances.”
Chemistry is a basic science.
Chemistry is between physics (rules of science) and biology
(order of science).
In chemistry, we investigate the fundamental building blocks of
matter and how those building blocks can arrange themselves
Consider water. It is composed of two elements which are
chemically bound together. It can easily be broken into its
components.
How do you solve problems?
Methods of Problem Solving
Cause and effect is one way to solve a problem. An
effect is observed and a cause is hypothesized.
Trial and error is another way to solve a problem.
This requires many tests to see if a solution can be
found.
Scientific method is yet another way of problem
solving. It is important because it uses formal,
time-tested, reliable, and reproducible sampling.
The Scientific Method
The scientific method is an organized way of seeking, processing,
testing and understanding certain types of information.
The steps of the scientific method are making observations,
formulating hypotheses, and performing experiments.
The Scientific Method
Observations occur when natural
phenomena are noted. They may
be quantitative or qualitative.
Hypotheses are attempts at
explanations. They are educated
guesses as to why a phenomenon
occurs. There are two kinds of
hypotheses, testable and untestable.
Experiments are carefully controlled,
repeatable procedures for gathering
data to test a hypothesis.
The Scientific Method
It is possible that a natural law may be found
during scientific investigation. A law describes
certain behaviors of the universe and may be in
mathematical form. Laws tell what happens.
Laws may be accepted, modified, or discarded
when new information comes to light. Example:
the law of conservation of mass
A theory is a collection of tested hypotheses,
often called a model. Theories explain why
experiments give certain results. Theories may
be accepted, modified, or discarded depending
on experimental results.
The First Great Theory of
Chemistry
The phlogiston theory was once believed to explain why
something burns. It was suggested by George Stahl in the 1700’s.
In that theory, a substance will burn if it has lots of “phlogiston” in
it, which it releases to the atmosphere during burning.
Once the “phlogiston” is gone, the substance no longer burns.
Ash was the “dephlogisticated” form of a substance since it no
longer had phlogiston in it.
It was believed that one could mix dephlogisticated material with
something that had lots of phlogiston to “rephlogisticate” it.
Antoine Lavoisier proved that this was not the way burning
worked in the late 1700’s after Joseph Priestly discovered oxygen.
The Importance of Measurement
A major part of the scientific method is experimentation. It is very
important that an experiment be carefully done so as to help prove (or
disprove) a theory.
Recording observations is essential so that results are repeatable by
those who follow.
There are two kinds of observations. Both provide important
information.
One kind of observation is quantitative. It gives results in numerical form
(numeric measurements). It is objective because it requires an
instrument. It involves a number and a unit.
The other kind of observation is qualitative. It gives results in a
descriptive form. It is subjective because it depends on the bias of the
observer.
Units of Measurement
There are two systems of measurement used in the United States---the
English system and the metric system. The metric system is more common
throughout the world and is the sole system used in science.
The need for standardization of units in science was met by the metric
system, also known as the SI system.
 In the SI system there are only seven fundamental units: meter, kilogram,
second, Ampere, candela, mole, and kelvin.
All other units are derived from these.
The meter is based on the distance light travels in a vacuum in 1/3x108 ths
of a second.
The second is based on the number of disintegrations from a cesium-133
atom.
Comparing and Contrasting
Measurement Systems
The English system is not The metric/SI systems are
widely used and are the
widely used.
foundation of scientific
The English system has no measurement.
base unit for a quantity.
The metric/SI systems use
The English system uses base units.
commas.
The SI system uses spaces.
Comparing and Contrasting
Measurement Systems
The English system has no
standard of comparison.
The English system has no
easy conversion from a small
unit to a larger unit
measuring the same
quantity.
The metric and SI systems
have standards. SI is based
on physical phenomena.
The metric/SI conversions
are based on powers of
10.
Comparing and Contrasting
Measurement Systems
The English system uses oF
for temperature.
The English system uses
fractions.
The metric system uses oC for
temperature whereas the SI
system uses K for
temperature.
The metric/SI system uses
decimals.
Metric Prefixes
Comparing Powers of 10
http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powers
of10/
What do we measure in an
experiment?
Mass is the amount of matter in an object. It is a measure of the
resistance of an object to a change in its state of motion. It is a constant
quantity and does not change when an object moves from place to
place. It is measured in grams or a unit involving grams.
Weight is a measure of the force of gravity exerted on a mass. It will
change due to changes in gravitational force. It is measured in
Newtons, which is not a fundamental unit but a derived unit. A Newton
is a kilogram • meter/second².
Volume is the amount of space an object occupies. It is measured in a
derived unit. It can be measured in liters (L) or any cubed unit of length.
One milliliter (mL) is equal to one cubed centimeter (cm³).
Instruments and Methods
Length is measured with a meter stick or metric ruler.
Mass is measured with a triple beam balance, a top-loading balance, or an
analytical balance since the mass of an object is compared to a standard
mass.
Volume is measured in different ways depending upon the substance to be
measured.
The volume of a liquid is measured with a graduated cylinder, a pipet, or a buret
but NEVER with a beaker or a flask.
The volume of a regular solid is measured by determining its dimensions and using
a volume formula.
The volume of an irregular solid is measured by displacement.
The volume of a gas is measured by trapping the gas in a container of known
volume while recording the temperature and pressure inside the container.
Uncertainty in Measurement
ALL measurements have a degree of uncertainty.
A measurement’s certainty depends on the measuring
device. The device has markings which indicate its
precision. We will discuss instrumental tolerances in lab.
Recording the correct number of significant figures from a
device lends reliability and consistency to measurements.
Significant figures are all those digits which can be read
from the device plus one digit which is estimated.
Please note that precision does not indicate accuracy.
Uncertainty in Measurement
This is a 25 mL buret. The liquid
level indicates how much has
already been dispensed. Notice
that it is graduated (marked)
into 0.1 mL units. This means
that the buret can be carefully
read to the nearest 0.01 mL. An
instrument is read to an
estimated digit between two
marks. What reading would you
give for this liquid?
Always check the instrument
you are using.
Accuracy vs. Precision
Closeness to a true
value obtained from a
reliable reference.
Dependent upon the
quality of the
measuring device.
Closeness of a set of
values
Reflects the
reproducibility of a
measurement
Not related to accurate
Only one measurement. value
Dependent upon the skill
of the person making the
measurement.
Accuracy vs. Precision
Kinds of Errors
There are two kinds of errors.
Random errors are also called indeterminate errors. When
this is the case, a measurement has an equal probability of
being too high or too low. These are difficult errors for which
to correct.
Systematic errors are also called determinate errors. They
occur in the same way each time the test is run. They will
always be high or always be low. These are usually the result
of poor technique.
Statistical analyses are used to combat these kinds of errors.
In lab we will use standard deviation analysis to determine the
precision of measurements.
Significant Figures in
Measurements
These are digits which may be read from an
instrument plus one digit which is estimated.
There are 100 mL graduated cylinders, 50 mL
graduated cylinders, 25 mL graduated cylinders and
10 mL graduated cylinders. Each instrument is
different. Check each instrument before using it to
determine how many figures may be read from it.
Then estimate one more figure.
The use of these lends reliability and consistency
to measurements.
Always check the instrument
you are using.
What digits are significant?
All nonzero digits are significant.
All captive zeroes are significant.
Ex. 50067 (these zeroes are “captive” between
nonzero digits)
All beginning zeroes are NOT significant.
Ex. 0.0056 (these zeroes are “beginning” zeroes and are not significant. 0.0056
has two significant figures)
Trailing zeroes are significant when a decimal is present.
Ex. 20.00 (since a decimal is present, these three “trailing” zeroes are significant)
Trailing zeroes are NOT significant when there is no decimal present unless
the final significant zero is noted with a bar over it.
Ex. 11000 (no decimal, so these “trailing” zeroes are not significant. 11000 has
two significant figures)
What about calculations using
significant figures?
When adding or subtracting, the answer may have
only as many DECIMAL PLACES as the least precise
number in the operation.
When multiplying or dividing, the answer may have
only as many SIGNIFICANT DIGITS as the least precise
number in the operation.
Rounding occurs ONLY at the end of a series of
calculations.
To round to a specific number of S.F., use only one
digit past that number of digits to determine whether
to round up or down.
Using Dimensional Analysis
Sometimes it is necessary to change from one unit to
another.
The method by which it is done is called unit factor
method, dimensional analysis, or simply conversion.
To convert from one unit to another
Use the equivalence statement that relates the two
units.
Multiply the given quantity by the unit factor which gives
the desired units.
Using Dimensional Analysis
Temperature Conversions
Temperature Conversions
Density
Density is the mass per unit of volume of a
substance.
It is an identifying property, or feature, of matter.
The common units are g/mL for liquids, g/cm3 for
solids, and g/L for gases, although any
mass/volume unit may be used. All of these units
are derived units.
The formula is D = Mass/Volume
Matter
Matter is anything that has mass and takes up space.
Mass is the amount of matter that a substance possesses.
Matter takes up space. Space is also known as volume.
Matter exists most commonly in three physical states: solids,
liquids, and gases
Forms of Matter
Forms of Matter
Solids
Have definite volume and shape
Have high density
Are almost incompressible
Expand only slightly when heated
True solids have definite melting points.
Forms of Matter
Liquids
Have definite volume
Take the shape of their container
Experience flow
Are almost incompressible
Are less dense than their solid form in most
cases
Expand slightly when heated
Maintain a horizontal surface when tipped.
Forms of Matter
Gases
Have no definite volume or shape.
Have a volume dependent upon temperature
and pressure.
Are very compressible.
Are less dense than the liquid form
Experience flow
Have very large spaces between the particles.
Are a high energy form of matter.
State Changes
When one form of matter changes into
another form of matter, a state, or phase,
change occurs. These are physical changes.
Solid to liquid
Liquid to gas
Solid to gas
Liquid to solid
Gas to liquid
Gas to solid
State Changes are Physical
Changes
Properties of Matter
Physical properties are those which can be observed
or measured without causing a substance to change its
identity. A physical change does not result in a change
of identity.
Some examples of physical properties are color, size,
smell, melting point, and conductivity.
There are two types of physical properties: extensive
and intensive.
Extensive properties are those dependent upon the amount
of substance present (Ex: mass, volume, length)
Intensive properties are all others (Ex: color, concentration)
Properties of Matter
Chemical properties are those which cause a substance to
change its features into something else. A new substance is
formed when a chemical property is observed. A chemical
change occurs in which one or more substances are
converted into something new. (Ex: flammability)
There are several evidences that a chemical change has
occurred. They may include large energy change, evolution
of gas, change in color, formation of a precipitate, odor
change.
 In a chemical reaction the starting substances are called
reactants while the ending substances are called products.
Composition of Matter
Matter is composed of atoms and molecules, which are the
smallest particles of matter which retain the identity of the
matter. Matter exists as pure substances and mixtures
An element is a pure substance made of only one type of atom.
A compound is a pure substance made of two or more different
atoms chemically bound together.
Classification of Matter
Pure Substances
Uniform composition
Definite composition
Homogeneous
Identical properties
Cannot be separated and
maintain its identity
Mixtures
Physical
combination(blend) of two
or more substances
Separable by physical
means
Variable composition
Components retain their
properties
Types of Pure Substances
Elements
All samples are identical.
Approximately 120
Approximately 90 are
naturally occurring
May be metal, metalloid, or
nonmetal
Exist as solids, liquids, or
gases
Compounds
All samples are identical.
Chemical combinations
Cannot be physically separated
and keep identity.
New properties that are different
from component properties
Definite composition
Homogeneous
Can be broken into elements by a
chemical change.
Types of Mixtures
Homogeneous
Heterogeneous
Also called a solution
Physical combinations
Physical combinations
Nonuniform within a
Uniform throughout a given sample
sample
Components are
distinguishable
Components uniformly
distributed
Separable by physical
Composition may vary from means
sample to sample
Separable by physical means
Examples of Physical Means of
Separating Mixtures
Simple
Distillation
Chromatography
https://www.youtube.com/watch?v=ZCzgQXGz9Tg
Elements
Elements are summarized on the Periodic Table.
They are represented by symbols of 1, 2, or 3 letters.
The vertical columns are groups or families whose
members have similar properties.
The horizontal rows or periods have members whose
properties change regularly as one moves from left to right.
All elements may be classified as representative (Gps 1-2
and 13-18) or transition (Gps 3-12).
The lanthanides and actinides are transition elements.
Kinds of Elements
Metals
Conduct heat and electricity.
Are malleable.
Are ductile.
Have luster.
Are solids, except for mercury which is a liquid.
Have high tensile strength.
Are found on the left side of the Periodic Table.
Kinds of Elements
Nonmetals
Do not conduct well.
Are brittle.
Are dull in color.
May be gases or solids, except bromine which is a
liquid.
Are found on the right side of the Periodic Table.
Metalloids or Semi-metals
Have properties of metals and nonmetals
Lie along a stair-step line on the Periodic Table.
Elemental Abundance
The most abundant element in the Earth’s crust
is oxygen. (Si, Al, Fe, Ca)
The most abundant metal in the Earth’s crust is
aluminum.
The most abundant element in our atmosphere
is nitrogen. (O2, Ar)
The most abundant element in our universe is
hydrogen.
The most abundant element in the human body
is oxygen.(C, H2)
Classification of Matter
Classification of Matter