Transcript Chapter 1 Chemistry: The Study of Matter

Chapter 1
Chemistry: The Study of Matter
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What is Chemistry?
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- the branch of science that deals with the
composition, structure and properties of
matter, with the changes that matter
undergoes in composition and with the
energy changes that occur during these
transformations.
Applied Chemistry is the using chemistry to
attain certain goals, in fields like medicine,
agriculture, and manufacturing (technology)
Pure chemistry gathers knowledge for
knowledge sake (academics)
Types of Chemistry
Analytical Chemistry studies
composition of substances.
 Inorganic Chemistry substances without
carbon
 Organic Chemistry compounds
containing carbon
 Biochemistry- Chemistry of living things
 Physical Chemistry studies behavior of
substances
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Chemistry is
A natural science.
 a language with its own vocabulary.
 a way of thinking.
 a body of knowledge.
 What are the types of knowledge?
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TYPES OF KNOWLEDGE
Scientific knowledge is empirical
in origin.
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EMPIRICAL KNOWLEDGE
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- Knowledge gained using the primary
senses – seeing, tasting, feeling,
hearing or smelling. Sometimes
instruments are used as aids to our
senses.
Authoritative Knowledge
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- knowledge we gain from experts e.g.
lawyers, doctors, people with
credentials.
Rational Knowledge
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- based on what are considered to be
rational truths e.g. If x=y and y=z then x
must equal z
Revealed knowledge
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- knowledge we accept on faith e.g. All
living animals today are descended
from those on board Noah’s Ark.
Intuitive Knowledge
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- knowledge possessed without knowing
where it comes from e.g. a mother
instinctively knows when her baby is in
need.
OBSERVATION VS
INTERPRETATION
Observations are always empirical.
Qualitative observations involve simple
descriptions.
Quantitative Observations involve
amounts
Interpretations involve reasoning
based on observations
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Scientific Method
A way of solving problems or answering
questions.
 Starts with observation- noting an
recording facts
 Hypothesis- an educated guess as to
the cause of the problem or answer to
the question.
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Scientific Method
Experiment- designed to test the
hypothesis
 only two possible answers
– hypothesis is right
– hypothesis is wrong
 Generates data observations from
experiments.
 Modify hypothesis - repeat the cycle
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Observations
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Hypothesis
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Experiment
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Cycle repeats many
times.
The hypothesis gets
more and more
certain.
Becomes a theory
A thoroughly tested
model that explains
why things behave a
certain way.
Theory can never
be proven.
 Useful because
they predict
behavior
 Help us form mental
pictures of
processes (models)
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Observations
Hypothesis
Experiment
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Another outcome is
that certain behavior
is repeated many
times
 Scientific Law is
developed
 Description of how
things behave
 Law - how
 Theory- why
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Observations
Hypothesis
Experiment
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Observations
Hypothesis
Theory
(Model)
Modify
Experiment
Prediction
Law
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Experiment
What is Matter?
Matter is anything that takes up space
and has mass.
 Mass is the amount of matter in an
object.
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Types of Matter
Pure Substance- made up of one kind of
matter
 Mixture- more than one kind of matter
 Homogeneous matter – looks the same
throughout (uniform composition)
examples silver, sugar, salt solution
 Heterogeneous matter – has parts with
different properties (composition is not
uniform) e.g. pizza, sand, salad
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Properties
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Words that describe matter (adjectives)
Physical Properties- a property that can be
observed and measured without changing the
composition of the substance.
(Identifying Properties)
Examples of Physical properties – color,
luster, malleability, ductility, transparency,
density, conductivity, hardness, solubility,
phase at room temperature, melting temp.,
boiling temp. etc
Chemical Properties
Chemical Properties- a property that
can only be observed by changing the
composition of the substance which
occurs during a Chemical Change (a
loss of the identity of the substance - a
new substance is produced).
 Chemical properties – describes the
tendency to react e.g. sodium reacts
with water; helium is non-reactive with
oxygen
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States of matter
Solid- matter that has definite shape
(can not flow) and has definite volume.
 Liquid- definite volume but takes the
shape of its container (flows).
 Gas- a substance without definite
volume or shape (can flow). Vapor- a
substance that is currently a gas but
normally is a liquid or solid at room
temperature.
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States of Matter
Definite Definite Temperature
Volume? Shape? increase
Solid
Liquid
Gas
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YES
YES
NO
Compressible?
YES
Small
Expansion
NO
NO
Small
Expansion
NO
NO
Large
Expansion
YES
Solid
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Freeze
Condense
Melt
Evaporate
Liquid
Sublimation
Gas
Physical Changes
A change that alters the appearance
without changing the composition.
(A change in physical properties)
 Examples?
 Boiled water is still water.
 Chemical changes - a change where a
new form of matter is produced.
 Examples?
 Iron rusting
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Mixtures
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Made up of two or more substances.
Has variable composition
Each substance keeps its properties.
Mixtures can be:
 Heterogeneous- mixture is not the same from
place to place (No uniform composition).
 Chocolate chip cookie, gravel, soil.
 Homogeneous- mixture is the same from
place to place (has uniform composition).
 Kool-aid, air.
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Solutions
Homogeneous mixture with molecules mixed
uniformly
 Solutions occur between any state of matter.
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Solid in liquid- Kool-aid
Liquid in liquid- antifreeze
Gas in a liquid – carbonated beverages
Gas in gas- air
Solid in solid - brass
Liquid in gas- water vapor
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Solutions
Like all mixtures, the components keep
their own properties.
 Components can be separated by
physical means
 Has one phase (uniform composition
and properties).
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Classification of Matter
Pure Substances
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Elements - simplest kind of matter only one kind of
atom present. Element cannot be broken down
into simpler substances
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Compounds - are substances that contain two or
more different kinds of atoms. The atoms are held
together by bonds to form molecules. Molecules
can be broken down by chemical methods.
When compounds are broken down, the
components have completely different properties
than the compound.
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Compound or Mixture
Compound
One kind of matterMolecule or atom
More than one kind of
matter- different molecules
or atoms
Made during a
Made through a
chemical change
physical change
Definite and uniform
composition
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Mixture
Variable in composition
Which is it?
Mixture
Element
Compound
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Chemical symbols
There are 112 elements
 Each has a 1 or two letter symbol
 First letter always capitalized second
never
 Don’t need to memorize
 Some from Latin of other languages
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Chemical Reactions
When one or more substances are changed
into new substances.
 Reactants- stuff you start with
 Products- What you make
 NEW PROPERTIES (New substance)
 Not easily reversed
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Indications of a chemical reaction
Energy absorbed or released
 Color change
 Gas produced
 Precipitate- solid that separates from
solution
 Not easily reversed
 ALWAYS THERE IS A NEW SUBSTANCE!
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Conservation of Mass
Mass can not be created or destroyed in
ordinary chemical or physical changes
(not true for nuclear changes. )
 All the mass can be accounted for.
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What about nuclear?
E = mc2
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 energy = mass x (speed of light)
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 speed of light = 3 x 10
 A little mass can make a lot of energy
 Law of Conservation of Mass - Energy
the total of the mass and energy
remains the same in any change
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Energy
The ability to do work.
 Work - cause a change or move an
object (Apply a force through a distance).
 Many types- all can be changed into the
other.
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Types of energy
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Potential- stored energy
Kinetic Energy- energy something has
because its moving
Heat- the energy that moves because of a
temperature difference.
Chemical energy- energy released or
absorbed in a chemical change (a change in
chemical bonds).
Electrical energy - energy of moving charges
Types of Energy
Radiant Energy- energy that can travel
through empty space (light, UV,
infrared, radio)
 All types of energy can be converted
into others.
 If you trace the source far enough back,
you will end up at nuclear energy.
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Energy Change during physical or
chemical change
changes – are those
processes that involve a loss of energy to
the surroundings (temperature of
surroundings goes up).
 Endothermic changes – are those
processes that absorb energy from the
surroundings (temperature of the
surroundings goes down).
 Exothermic
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Conservation of Energy
Energy can be neither created or
destroyed in ordinary changes (not
nuclear), it can only change form.
 Its not just a good idea, its the law.
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