Chemistry

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Chemistry

• Dr. Michael P. Gillespie

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Chemistry

• Chemistry is the study of matter, its chemical
  and physical properties, the chemical changes it
  undergoes, and the energy changes that accompany
  those processes.
• Matter is anything that has mass and occupies
  space. The changes that matter undergoes always
  involve either gain or loss of energy.
• Energy is the ability to do work to accomplish
  some change.

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Chemistry

• The study of chemistry involves matter, energy,
  and their interrelationship.
• Matter and energy are at the heart of chemistry.

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Scientific Method

• The scientific method is a systematic approach to
  the discovery of new information.
• It is a way of gaining information (facts) about
  the world by forming possible solutions to
  questions.
• Rigorous testing is employed to determine if the
  proposed solutions are supported.

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Basic Assumptions In Science

• There are specific causes for events observed in
  the natural world.
• The causes for events in nature can be
  identified.
• There are general rules or patterns that describe
  what happens in nature.

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Basic Assumptions In Science

• Repeated events probably have the same cause.
• What one person observes can be observed by
  others.
• The same fundamental rules apply, regardless of
  when or where they occur.

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Cause and Effect

• Some events are correlated (happen together).
• Some events have a cause and effect relationship
  (an event is a direct result of a previous event).

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Components of the Scientific Method

• Observation
• Hypotheses
• Openness to new information and ideas
• Willingness to submit ones ideas to the scrutiny
  of others

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Observation

• Observations are made using our senses or an
  extension of our senses.
• Observations are careful, thoughtful recognition
  of an event.

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Questioning and Exploration

• Optimal questions lend themselves to
  experimentation.
• Explore other sources of knowledge relevant to
  the question.

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Hypothesis

• A hypothesis is a statement that provides a
  possible answer to a question or an explanation
  for an observation that can be tested.

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Characteristics of a Good Hypothesis

• Logical
• Account for all relevant information
• Predict future events
• Testable
• Use the simplest hypothesis with the fewest
  assumptions

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Einstein

• Make everything as simple as possible, but not
  simpler.

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Testing a Hypothesis

• A good hypothesis is testable.
• It can be either supported or disproved.
• If a hypothesis cannot be disproved, confidence
  in it increases.
• New information can encourage scientists to
  reformulate an hypothesis.

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Methods for Testing a Hypothesis

• Collect relevant information.
• Make additional observations.
• Devise an experiment.

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Experiment

• An experiment is a re-creation of an event or
  occurrence in a manner that allows the scientist
  to support or disprove a hypothesis.

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Variables

• Variables are individual factors that help
  determine the outcome of an event.

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Controlled Experiment

• A controlled experiment is one in which only one
  variable is present.
• Two groups
• Control group no manipulation of the variable.
• Experimental group a group in which one
  variable is manipulated.

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Variables

• Independent variable is manipulated in the
  experiment by the scientist.
• Dependent variable will change as a result of
  manipulation of the independent variable.
• There should be only one independent variable in
  an experiment.
• Be careful not to introduce additional variables
  into the experiment.

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Development of Theories and Laws

• If new evidence consistently and repeatedly
  supports the original hypothesis and other
  related hypotheses, we begin to see patterns
  emerge.
• Scientific theories and laws come into existence.

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Inductive Reasoning

• The process of developing general principles from
  the examination of many specific facts is known
  as inductive reasoning or induction.

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Deductive Reasoning

• The process of using general principles to
  predict the specific facts of a situation is
  called deductive reasoning or deduction.

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Scientific Theory

• A theory is a widely accepted, plausible, general
  statement about fundamental concepts in science
  that explain why things happen.
• A theory is a very broad statement, which is the
  result of years of observation, questioning,
  experimentation, and data analysis.

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Theory Vs. Hypothesis

• A hypothesis provides a possible explanation for
  a specific question whereas a theory is a broad
  concept that shapes how scientists look at the
  world and how they frame their hypothesis.

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Scientific Law

• A scientific law is a uniform or constant fact of
  nature that describes what happens in nature.

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Theory Vs. Law

• Theory
• Describes why things happen
• Examined repeatedly
• Independently verified
• Excellent predictors of how nature behaves

• Law
• Describes what happens in nature
• Examined repeatedly
• Independently verified
• Excellent predictors of how nature behaves

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Properties of Matter

• Properties are characteristics of matter and are
  classified as either physical or chemical.

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States of Matter

• Three states (phases) of matter
• Solid state
• Liquid state
• Gaseous state.

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States of Matter

• The phases of matter are determined by the
  following
• The amount of kinetic energy molecules have.
• The strength of the attractive forces between
  molecules.
• The arrangement of molecules.

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Solid

• A solid consists of molecules with strong
  attractive forces and low kinetic energy.
• The molecules vibrate in place and are at fixed
  distances from one another.

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Liquid

• A liquid has molecules with enough kinetic energy
  to overcome the attractive forces that hold the
  molecules together.
• The molecules are still strongly attracted to one
  another, but they are slightly farther apart.

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Liquid

• The molecules can slide past one another.
• Liquids change shape, but they maintain their
  volume.
• Liquids flow and are called fluids.

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Gas

• A gas is made of molecules that have a great deal
  of kinetic energy.
• The attraction of the molecules to one another is
  overcome by the speed with which the individual
  molecules move.

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Gas

• The molecules collide against one another and
  push each other apart.
• Therefore, gases expand to fit their container.
• Vapor is the gaseous form of a substance that is
  usually in a liquid phase.

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States of Matter
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Water

• Water is the most common example of a substance
  that can exist in all three states over a
  relatively small temperature range.

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States of Water
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Physical Change

• A physical change produces a recognizable
  difference in the appearance of a substance
  without causing any change in its composition or
  identity.
• Conversion of water from one state to another
  constitutes a physical change.

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Physical Properties of Matter

• A physical property can be exhibited, observed or
  measured without changing the composition or
  identity of a substance.

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Physical Properties

• A practical application of this concept is in the
  separation of materials based upon their physical
  properties.

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Chemical Properties of Matter

• Chemical properties can be observed only through
  chemical reactions and result in a change in the
  composition of the material.
• The substances internal structure must be affect
  to observe chemical properties.

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Chemical Reaction

• A chemical reaction is a process that produces a
  change in matter by rearranging, removing,
  replacing, or adding atoms to produce new
  substances.
• This is achieved by either forming or breaking
  chemical bonds.
• A chemical reaction involves atoms interacting
  with other atoms to fill their outermost energy
  shell.

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Chemical Reaction
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Chemical Reaction

• The interacting atoms become attached or bonded
  to one another.
• Two types of bonds
• Ionic
• Covalent

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Ionic Bonds

• A positively or negatively charges atom or
  molecule is called an ion.
• Ionic bonds are formed after atoms transfer
  electrons to achieve a full outermost energy
  level.
• Electrons are donated or received during the
  transfer to form positive or negative ions
  (ionization).

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Ionic Bonds
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Covalent Bonds

• A covalent bond is a chemical bond formed by the
  sharing of electrons.
• A covalent bond in which a single pair of
  electrons is shared is called a single covalent
  bond (single bond).
• Double bond two pairs of electrons are shared.
• Triple bond three pairs.

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Hydrogen Bonds

• Hydrogen bonds are due to the unequal sharing of
  electrons and the resulting polar nature of the
  molecule.
• Hydrogen bonds can be either intermolecular or
  intramolecular.
• Hydrogen bonds hold molecules together, they do
  not bond atoms together. Therefore, they are not
  true chemical bonds.

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Intensive Vs. Extensive Properties

• Properties can be classified according to whether
  or not they depend upon the size of the sample.

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Intensive Properties

• An intensive property is a property of matter
  that is independent of the quantity of the
  substance.
• Density, boiling and melting points, and specific
  gravity are intensive properties.
• The boiling point of a single drop of water is
  exactly the same as the boiling point of a liter
  of water.

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Extensive Properties

• An extensive property depends on the quantity of
  a substance.
• Mass and volume are extensive properties.
• There is an obvious difference between 1 gram of
  silver and 1 kg of silver.

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Classification of Matter

• Chemists look for similarities in properties
  among various types of materials.
• The most useful classification systems are based
  on composition.
• All matter is either a pure substance or a
  mixture.

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Pure Substances

• A pure substance has only one component.
• Elements and compounds are both pure substances.
• An element is a pure substance that cannot be
  changed into a simpler form of matter by any
  chemical reaction.
• A compound is a substance resulting from the
  combination of two or more substances in a
  definite, reproducible way.

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Water

• Pure water is a pure substance.
• The elements hydrogen and oxygen may combine to
  form the compound water, H20.

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Mixture

• A mixture is a combination of two or more pure
  substances in which each substance retains its
  own identity.
• Alcohol and water may be combined in a mixture.
  They coexist as pure substances because they do
  not undergo a chemical reaction they exist as
  thoroughly mixed discrete molecules.

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Mixture

• The substances are not in set proportions.
• There are an infinite number of combinations of
  quantities of alcohol and water that can be
  mixed.
• You can have a small amount of water and a large
  amount of alcohol or vice versa.
• Either way, it is still an alcohol-water mixture.

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Types of Mixtures

• A homogenous mixture has a uniform composition.
  Its particles are well mixed, or thoroughly
  intermingled. (i.e. alcohol-water)
• A heterogenous mixture has a nonuniform
  composition. (i.e. salt and pepper or concrete).

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Solutions

• A solution is a liquid mixture of ions or
  molecules of two or more substances.
• The process of making a solution is called
  dissolving.
• The solvent is the component present in the
  larger amount.
• The solute is the component that dissolves into
  the solvent.

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Solutions

• Aqueous solution a solid, liquid, or gas
  dissolved in water.
• Gaseous solution a mixture of gasses such as
  air.

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Concentrations

• Concentration is a measure of the number of
  particles of a substance, or the mass of those
  particles, that are contained in a specified
  volume.
• The amounts of solute and solvent are the
  concentration of a solution.

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Data

• A scientific experiment produces data. Each
  piece of data is the result of a single
  measurement or observation. Mass, length,
  volume, time, temperature, and energy are common
  types of data obtained from chemical experiments.

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Data
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Results

• Results are the outcome of an experiment. Data
  and results may be identical however, typically,
  several related pieces of data are combined and
  logic is used to produce a result.

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Unit

• A unit of measurement is a definite amount of a
  physical quality.
• A unit defines the basic quantity of mass,
  volume, time, or whatever quantity is being
  measured.

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Experimental Quantities

• Mass
• Length
• Volume
• Time
• Temperature
• Energy

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Mass Vs. Weight

• Mass describes the quantity of matter in an
  object.
• Weight and mass are NOT synonymous.
• Weight is the force of gravity on an object.
• Weight mass acceleration due to gravity.

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Mass Vs. Weight

• When gravity is constant, weight and mass are
  directly proportional, but gravity is not
  constant.
• Mass is independent of gravity. It is the result
  of a comparison of an unknown mass with a known
  mass called a standard mass.

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Atomic Mass Unit

• An atom of a substance has a very tiny mass.
• An atom of hydrogen has a mass of 1.661 X 10-24
  g.
• One atomic mass unit is a more convenient way to
  represent the mass of one hydrogen atom, rather
  than 1.661 X 10-24 g.
• Units should be chosen to suit the quantity of
  the item being described.

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Length

• Length is the distance between two points.
• The standard metric unit of length is the meter.
• Larger distances are measured in kilometers,
  smaller distances are measured in centimeters or
  millimeters. Very small distances such as the
  distances between atoms are measured in
  nanometers.

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Volume

• Volume is the space occupied by an object.
• The standard metric unit of volume is the liter.
• The volumetric flask is designed to contain a
  specified volume of liquid.
• The graduated cylinder, pipet, and buret dispense
  a desired volume of liquid.

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Time

• The standard metric unit of time is the second.
• Matter can be characterized by the time required
  for a certain process to occur.
• The rate of a chemical reaction is a measure of
  change as a function of time.

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Temperature

• Temperature is the degree of hotness of an
  object.
• The common temperature scales are Fahrenheit
  (F), Celsius (C), and Kelvin (K).
• Two convenient reference points that are used to
  calibrate a thermometer are the freezing and
  boiling points of water.

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Energy

• Energy is the ability to do work.
• It can be categorized as either kinetic energy or
  potential energy.
• Kinetic energy is the energy of motion.
• Potential energy is the energy of position. It
  is stored energy that is not yet doing work.
• All energy is either kinetic or potential.

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Forms of Energy

• The principal forms of energy include
• Light
• Heat
• Electrical
• Mechanical
• Chemical

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Characteristics Of Energy

• Energy cannot be created or destroyed.
• Energy may be converted from one form to another.
• Conversion of energy from one form to another
  always occurs with less than 100 efficiency.
• All chemical reactions involve either a gain or
  loss of energy.

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1st Law of Thermodynamics

• The 1st law of thermodynamics is also known as
  the law of conservation of energy.
• Energy is neither created or destroyed.
• Energy can be converted from one form to another,
  but the total energy remains constant.

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Concentration

• Concentration is a measure of the number of
  particles of a substance, or the mass of those
  particles, that are contained in a specified
  volume.
• Concentration is used to represent m ixtures of
  different substances.
• i.e. concentration of oxygen in the air.

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Density

• Density is the ratio of mass to volume.
• d mass / volume m / V
• It is not dependent upon the quantity of the
  material present and is therefore an intensive
  property.
• Each substance has a unique density.
• One milliliter of air and one milliliter of iron
  do not weigh the same amount.

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Specific Gravity

• Values of density are often related to a
  standard, well-known reference, the density of
  pure water at 4C.
• This referenced density is called the specific
  gravity, the ratio of the density of the object
  in question to the density of pure water at 4C.
• specific gravity density of object g/mL) /
  density of water (g / mL)
• The density of water at 4Cnis 1.00 g/mL.