Transcript Chapter 1 - Introduction to Chemistry

Introduction to Chemistry
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Study of the _________________
of matter and the
_________________ matter
undergoes.
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Organic chemistry Inorganic chemistry Analytical chemistry Physical chemistry
Biochemistry -
Understanding Concepts
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Chemistry deals with scientific facts facts that can be discovered by making
observations and doing experiments.
It is often necessary to rely on
information that others have discovered.
Diamond
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Hardest known substance.
A form of the element carbon.
Highly ordered molecular structure.
Not the most stable form of carbon.
Macro vs. Micro
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_________________ - things you see
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with the unaided eye or large scale
experimenting.
_________________ - things too
small to see with the unaided eye or small scale experimenting.
Matter and Change
Matter
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Anything that has
_________________ and takes up
_________________.
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Everything is made up of matter.
Definitions for Components of Matter
_________________ - the simplest type of substance with unique
physical and chemical properties. An element consists of only
one type of atom. It cannot be broken down into any simpler
substances by physical or chemical means.
_________________ - a structure that consists
of two or more atoms that are chemically
bound together and thus behaves as an
independent unit.
Definitions for Components of Matter
_________________ - a substance
composed of two or more elements
which are chemically combined.
_________________ - a group of two
or more elements and/or
compounds that are physically
intermingled.
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_________________ - amount of
matter the object contains - measured
in grams.
_________________ - matter that has
uniform and definite composition (pure
substances) - contain only one kind of
matter.
Physical Properties
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Quality or condition of a substance that
can be observed or measured without
changing the substance’s composition.
Color
odor
hardness
density
melting & boiling points
solubility
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Physical properties help chemists
_________________ substances.
Physical Change
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Matter can be changed in many ways
without changing the chemical
composition of the material.
Cutting
• Dissolving
• Crack
Grinding
• Melting
• Break
Boiling
• Crush
Bending
• Freezing
Tearing
• Condensing
Melting or Freezing of Water
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Melting ice into liquid is a physical
change, along with changing liquid to
steam and steam to condensation.
There is no alteration to the chemical
composition of water, only a change of
state.
Chemical Property
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The ability of a substance to undergo a
chemical reaction and to form new
substances.
Chemical properties are only observed
when a substance undergoes a
chemical change.
A chemical change always results in a
change in the chemical composition of
the substances involved.
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Burning
Decompose
Rust
Explode
Corrode
Rot
Physical Properties
those which the substance
shows by itself without
interacting with another
substance such as color, melting
point, boiling point, density
Chemical Properties
those which the substance shows
as it interacts with, or transforms
into, other substances such as
flammability, corrosiveness
Figure 1.1
The distinction between physical and chemical change.
A Physical change
B Chemical change
Sample Problem 1.1
Distinguishing Between Physical and
Chemical Change
PROBLEM: Decide whether each of the following process is primarily a
physical or a chemical change, and explain briefly:
(a) Frost forms as the temperature drops on a humid winter night.
(b) A cornstalk grows from a seed that is watered and fertilized.
(c) Dynamite explodes to form a mixture of gases.
(d) Perspiration evaporates when you relax after jogging.
(e) A silver fork tarnishes slowly in air.
States of Matter
States of Matter
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- definite
shape and volume.
_________________
Particles are packed tightly together.
 Almost incompressible.
 Expand only slightly when heated.
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- indefinite
shape and definite volume.
_________________
In close contact with one another.
 Liquids can flow.
 Almost incompressible.
 Tend to expand when heated.
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Gas - indefinite shape and
volume.
Gas particles are far apart.
 Easily compressed.
 Expand without limit to fill any space.
 _________________ - describes the
gaseous state of a substance that is
generally a liquid or solid at room
temperature (different than a gas).
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Classifying Mixtures
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Physical blend of two or more
substances.
Compositions may vary.
Heterogeneous Mixture
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Not uniform in composition.
If you were to separate the mixture into
portions, each portion would be
different from the other.
Homogeneous Mixture
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Completely uniform throughout.
Components are evenly distributed
throughout.
Separate the mixture into portions and
the portions would be the same.
Also called _________________ - may
be gases, liquids, or solids.
Scientific Method
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An important scientific discovery may
involve some luck, but one must be
prepared to recognize the lucky event.
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Alexander Fleming
Most advances in science involves little
or no luck, but a logical systematic
approach to the solution of a difficult
problem.
Scientific Method
Logical approach to the solution
of scientific problem.
 Related to ordinary common
sense.
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Observation
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Using your senses to
obtain information directly.
Hypothesis
A possible _________________ or
_________________ for what is
observed.
 A proposal
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Experiment
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Test the hypothesis.
For the results of an experiment to
be accepted, the experiment must
produce the same result no matter
how many times it is repeated, or
by whom.
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If the experimenting does not
support the hypothesis, the
hypothesis must be changed.
The process of testing the
hypothesis must be carried out until
the hypothesis fits all the observed
experimental facts.
Theory
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Once a scientific hypothesis meets
the test of repeated
experimentation, it may become a
theory.
A theory is a broad and extensively
tested explanation of why
experiments give certain results.
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A theory can never be proved
because it is always possible that a
new experiment will disprove it.
Theories give you the power to
predict the behavior of natural
systems.
Scientific Law
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Concise statement that summarizes the
results of many observations and
experiments.
Describes a natural phenomenon
without attempting to explain it.
Can be expressed as a mathematical
equation.
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A _________________ states
what happens; a
_________________ explains
why.
International System of Units
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The Metric System
Metric System
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The metric system was developed in
France in the 1790s.
The metric system missed being
nationalized in this country by one vote
in the late 1700s.
Metric System
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Based on the powers of 10.
Countries that have not officially
adopted the Metric System include:
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United States
Liberia, Africa
Berma, Southeast Asia
Why should we use the metric
system?
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We are living in a metric world where
just about every country, except the
USA, uses the metric system, and other
countries are now telling us that they
don't want to buy some of the products
manufactured by U.S. companies if they
aren't made to metric sizes (and if they
aren't labeled in metric units).
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Many European Union (EU) countries,
which have been good customers of
U.S. companies, don't allow products
into their countries unless they are
made to metric system standards. We
must operate in the world marketplace,
and we can't stay competitive if we
don't provide metric goods.
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In addition, beginning on January 1,
2010, the EU will require products to be
labeled solely in metric measurements.
If US laws are changed to allow metriconly labeling, it will be easier for US
companies to comply with that
directive.
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With 99% of the rest of the world using
metric, there is no chance we can
persuade them to use our inches and
pounds.
Metric System
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Based on the powers of 10
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millicentideci(basic unit)
decahecta
kilo-
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Between each step, there is an increase
by a power of 10.
10 mm = 1 cm
10 cm = 1 dm
10 dm = 1 m
10 m = 1 dam
10 Dm = 1 hm
10 Hm = 1 km
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Yotta
Zetta
Exa
Peta
Tera
Giga
Mega
Kilo
Basic Unit
Milli
Micro
Nano
Pico
Femto
Atto
Zepto
Yocto
Y
Z
E
P
T
G
M
k
m
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n
p
f
a
z
y
1024
1021
1018
1015
1012
109
106
103
1
10-3
10-6
10-9
10-12
10-15
10-18
10-21
10-24
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As you move from a small to large, you
move the decimal that many places to
the left.
As you move from large to small, you
move the decimal that many places to
the right.
Units of Length
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SI unit = meter (m)
1 meter = 1000 mm
1 meter = 1.09 yards = 39.36 inches
1 km = 1000 meters
1 km = 0.62 miles
1 inch = 2.54 cm
Units of Length
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Unit used for measuring atoms in
chemistry is the Ångström – Å = 10-8
cm
Centimeter is about the diameter of a
dime
Millimeter is about the thickness of a
dime
Units of Volume
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_________________ occupied by any
sample of matter.
SI unit = m3
More common unit = liter (L)
1 L = 1000 mL
1 mL = 1 cm3
Units of Volume
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Unit of volume for a solid
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length x width x height = volume of a
regular shaped object (cm3)
1 mL = 1 cm3
One liter is a little more than a quart
One cup is 250 mL
Units of Mass
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_________________ - measure of the
quantity of matter in an object.
_________________ - force that measures
the pull of gravity on any given mass.
SI unit = kilogram (kg)
1 kg = 1000 grams (g)
1 kg = 2.12 pounds
One gram is about the mass of a paperclip
Units of Temperature
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Kelvin Scale
0 K = -273C
Degree Celsius (°C)
0°C = 32°F (freezing point of water)
100°C = 212°F (boiling point of water)
Conversion between Temperatures
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F to C
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(C x 1.8) + 32 = F
C to F
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(F – 32)  1.8 = C
Time
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SI Unit = second (s)
Graphing
Graphing
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The relationship between two variables
in an experiment is often determined by
graphing the experimental data.
The graph is a “picture” of the data.
Graphing Information
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_________________ Variable
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manipulated variable
X-axis (horizontal)
_________________ Variable
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responding variable
Y-axis (vertical)
Time (seconds)
Distance
(meters)
0
5
10
15
20
25
30
0
3.5
6.2
10.1
17.3
26.5
37.1
Time vs. Distance
40
37.1
Distance (meters)
35
30
26.5
25
20
17.3
15
10.1
10
6.2
5
3.5
0
0
0
10
20
Time (seconds)
30
40
Scientific Measurement
Types of Measurements
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_________________ measurements -
results are given in descriptive,
non-numerical form.
_________________ measurements results are given in definite form,
usually as numbers and units.
Scientific Notation
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A number written as the product of two
numbers: a coefficient and 10 raised to
a power.
3.6 x 105
The coefficient is always written as a
number greater than one and smaller
than ten - only one number to the left
of the decimal.
Multiplication & Division
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In multiplication of scientific notation
values, multiply the coefficients and add
the exponents.
In division of scientific notation values,
divide the coefficients and subtract the
exponents.
Addition & Subtraction
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Before adding or subtracting, the
exponents must be the same.
After the exponents are the same, add
or subtract the coefficients with the 10
raised to the power of.
Significant Figures
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It is important to be honest when
reporting a measurement, so that it
does not appear to be more accurate
than the equipment used to make the
measurement allows. We can achieve
this by controlling the number of digits,
or _________________, used to report
the measurement.
Rule 1:
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All nonzero digits are significant.
Rule 2:
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Zeros within a number are always
significant. Both 4308 and 40.05
contain four significant figures.
Rule 3:
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Zeros that do nothing but set the
decimal point are not significant. Thus,
470,000 has two significant figures.
Rule 4:
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Trailing zeros that aren't needed to hold
the decimal point are significant. For
example, 4.00 has three significant
figures.
How many sig figs?
(a) 0.0030 L
(d) 0.00004715 m
(b) 0.1044 g
(e) 57,600. s
(c) 53,069 mL
(f) 0.0000007160 cm3
Rules for Sig Figs in Answers
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When combining measurements with different
degrees of accuracy and precision, the
accuracy of the final answer can be no
greater than the least accurate measurement.
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This principle can be translated into a simple
rule for addition and subtraction:
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When measurements are added or
subtracted, the answer can contain no more
decimal places than the least accurate
measurement.
Addition & Subtraction
Example: adding two volumes
83.5 mL
+ 23.28 mL
106.78 mL = 106.8 mL
Example: subtracting two volumes
865.9
mL
- 2.8121 mL
863.0879 mL = 863.1 mL
Rules for Sig Figs in Answers
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The same principle governs the use of
significant figures in multiplication and
division: the final result can be no more
accurate than the least accurate
measurement.
In this case, however, we count the
significant figures in each measurement, not
the number of decimal places:
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When measurements are multiplied or
divided, the answer can contain no more
significant figures than the least accurate
measurement.
Multiplication & Division
9.2 cm x 6.8 cm x 0.3744 cm = 23.4225 cm3 = 23 cm3
Rounding
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When the answer to a calculation
contains too many significant figures, it
must be rounded off.
Rounding
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If the digit is smaller than 5, drop this
digit and leave the remaining number
unchanged. Thus, 1.684 becomes 1.68.
If the digit is 5 or larger, drop this digit
and add 1 to the preceding digit. Thus,
1.247 becomes 1.25.
Uncertainty in Measurements
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_________________ - measure of how
close a measurement comes to the
actual or true value of whatever is
measured.
_________________ - measure of how
close a series of measurements are to
one another. (depends on multiple
measurements)
precise and accurate
precise but not accurate