Foundations%20of%20chemistry

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Foundations of chemistry

• Chapter 1

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Key concepts in this unit

• The scientific method
• The definition of chemistry
• Matter and energy
• States of matter
• Chemical and physical properties
• Chemical and physical changes
• Measurements in chemistry
• Units and SI system
• Uncertainty in measurement precision and
  accuracy
• Using dimensional analysis
• Mass percent
• Density and specific gravity
• Heat, temperature, specific heat

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The Scientific Method

• The generally accepted approach to solving
  problems in the sciences.
• The pattern is used to generate rigorous,
  reliable, and repeatable research procedures in
  the discovery of new scientific concepts.

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Steps in the scientific method

• An initial question usually starts the process
• Experiments/observations-
• Law-
• Hypothesis-
• Hypothesis may lead to ________
• Theory-

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ChemistryA study of matter and energy

• Matter
• Mass
• D C 1317spiritual things are also material
• Since matter is everywhere, a basic understanding
  of chemistry is essential.
• Energy
• Types of energy
• kinetic
• potential

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Laws of conservation

• Conservation of matter
• Conservation of energy
• Most chemical changes (reactions) observe these
  two laws.
• Nuclear reactionschanging matter into energy
• Emc2
• Conservation of matter and energy
• D C 1317

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Classifying matterstates of matter
SOLID LIQUID GAS
Shape
Density
Compressibility

• Other (exotic) states of matter
• Plasma
• Bose-Einstein condensate
• Supercritical fluid
• More?

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Properties of matter

• Physical properties
• Chemical properties
• Which are physical? Chemical?
• Melting point
• density
• flammability
• conductivity
• Matter states

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Properties of matter

• Intensive properties
• Extensive properties
• Which are intensive? Extensive?
• mass
• volume
• density
• melting point
• boiling point

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Changes in matter

• Physical changes
• Chemical changes
• Chemical changes also called chemical reactions
• Which changes are physical? Chemical?
• Combustion
• Evaporation
• Dissolution
• Fission

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Mixtures

• Two types
• Heterogeneous
• Homogeneous. A homogeneous mixture also called a
  ____________
• Water and salt vs water and sand.
• A homogeneous mixture may have some physical
  properties differing from its components (such as
  melting point or boiling point)
• NO change in chemical properties.

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• Mixtures may be separated by physical means.
  Examples
• Distillation
• Filtration
• Chromatography

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Chromatography essentials

• Mobile phase
• Stationary phase
• Solvent front

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Gas chromatography
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Substances

• Substances include elements and compounds. They
  CANNOT be separated by physical means.
• Compounds ______________________________________
  ______________________________________
• Compounds follow law of constant composition
• Elements _______________________________________
  _____________________________________

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System Internationale (SI)internationally
accepted system of measurement

• SI units
• Mass
• Length
• Volume
• Temperature

• Prefixes
• 109 giga (G)
• 106 mega (M)
• 103 kilo (k)
• 10-2 centi (c)
• 10-3 milli (m)
• 10-6 micro (?)
• 10-9 nano (n)
• 10-12 pico (p)

• Know all SI units
• and prefixes on p 17 of text !!!

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Uncertainty in measurement

• Two types of numbers
• Exact numbers (counting or defined)
• Measured numbers

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Accuracy and precision

• Accuracy how close a single measurement is to a
  true value.
• Precision how close a group of measurements are
  to each other

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Precision vs. accuracy
Precise, but not accurate
Accurate and precise
Accurate, but not precise
Neither accurate nor precise
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Significant figures

• Used to illustrate how accurate and precise the
  measurement is.
• Measurements are reported where the last digit is
  the uncertain one.
• 5.0 g vs. 5.00 g. Which measurement is believed
  to be more accurate and precise?

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Significant figure rules

1. Exact numbers have unlimited number of
   significant digits.
2. Nonzero digits are always significant.
3. Zeros between nonzero digits are always
   significant
4. Zeros at the beginning of a number (placeholders)
   are never significant
5. Zeros at the end of a number after the decimal
   point are always significant
6. Zeros at the end of a number without a decimal
   point are not very clear.

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Scientific notation

• Two purposes for SN
• Removing ambiguity of zeros
• Handling very large or very small quantities.
• number N ? 10x
• N is a number between 1 and 10.
• x is an exponent
• Using a calculator, SN exponents entered with the
  EXP or EE button.
• 4.5 1014 entered as 4.5 EE 14

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Significant figures in calculations

• Addition and subtraction
• Multiplication and division
• When carrying on several steps, retain extra
  digits from calculator in intermediate answers to
  avoid rounding errors. Round answer according to
  sig. fig. rules.

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Dimensional analysis

• Any number multiplied by 1 is the same number
• (a ? 1 a)
• Conversion factor a fraction expressing the
  same value in different units
• ? multiplying any number by a conversion factor
  multiplying number by 1

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Process for dimensional analysis

• ALWAYS CARRY UNITS. They are essential in
  determining if a calculation was done correctly.
• Lets try some examples

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Percent by mass

• Use any mass units, so long as you are consistent.

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Density

• Ratio of mass per unit volume
• D m/V
• Density is an intensive property.
• Specific gravity is ratio of density of substance
  to density of water (1.00 g/mL _at_ room temp)
• Sp. Gr. Dsub/Dwater
• Sp. Gr. is numerically equal to D, but it is
  unitless
• Examples

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Heat and temperature

• Temperature indicates ____________________________
  _____
• Heat flows in which direction?
• Temperature units
• Celsius
• Kelvin
• Fahrenheit
• Conversions (just one or two)

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Specific heat

• Amount of heat required to heat one gram of a
  substance one degree Celsius (or Kelvin) w/o
  changing phase.
• specific heatC
• Heatq
• Massm
• Temperature change??T
• Is C an extensive or intensive property?

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Using specific heat

• Some examples
• Calculating specific heat of a substance
• q mC(Tf Ti)
• Transfer of heat from one substance to another
• qA -qB