John A. Schreifels

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Chemistry 211

• General Chemistry
• Ebbing and Gammon

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WHY STUDY CHEMISTRY?

• Chemistry is important to us all.
• Chemistry major is reasonably likely to find a
  job after graduation!
• Career advisors suggest a broad background.
• Many students end up doing chemistry after
  graduation because of the overcrowding in their
  field.

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SUCCESSFUL STRATEGIES

• Memorize strategies not equations!
• Study a lot!
• Self-evaluate after quiz results.
• Old examinations on the WEB.

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LEARNING TOOLS

• Textbook read chapter work lots of problems.
• Other textbooks (check the library as well as
  used bookstores.
• Tutoring center Student Union Building II Room
  2002A
• Classmates
• General Chemistry WEB page http//osf1.gmu.edu/j
  schreif/genchem/
• Instructor

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Chapter 1 Matter and Measurement

• Overview
• The Study of Chemistry
• Classifications of Matter
• Properties of Matter
• Units of Measurement
• Uncertainty in Measurement
• Dimensional Analysis
• Basic Math Concepts (see Appendix A)

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The Study of Chemistry

• Chemistry the study of the composition,
  properties and transformations of matter.
• Matter physical material of the universe.
• Elements basic building blocks of all other
  forms of matter.
• Atoms small particles derived from one the
  elements. All matter can be described in terms
  of the interactions of atoms with each other.
• Molecules (compounds) combination of two or
  more atoms. Most common form for atoms.

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Classification of Matter

• States of Matter
• Solid Rigid StructureLiquidLess Rigid Structure
  GasLoose StructurePlasmaGaseous atoms or small
  molecules in an ionized state.
• Substances and mixtures
• Substance matter having a fixed composition and
  distinct properties. Can be either an element or
  a compound.
• Element a substance containing only one type of
  atom. E.g. Na, H2.
• Compound a substance composed of atoms from two
  or more elements chemically combined.
• Mixture matter composed of two or more
  substances. Air composed of hydrogen, oxygen,
  nitrogen, etc.

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Classifications of Matter (contd)

• Mixturescan be separated by physical means into
  two or more substances.
• Homogeneous Composition constant in all parts of
  sample
• Heterogeneous Composition not-constant.
• Mixtures separated by
• Filtration Mixture consists of a solid and
  liquid liquid separated by filtration.
• Chromatography Separates mixtures by
  distributing components between a mobile and
  stationary phase.
• Distillation Liquid mixture is boiled
  components in the mixture boil off at different
  temperatures.

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LAW OF DEFINITE PROPORTIONS

• Law of definite proportions a pure compound
  always contains definite (constant) proportions
  by mass of the elements in the compound.
• E.g. Data from analysis of cyclopropane was found
  to contain 6.00 g of carbon and 1.00 g of
  hydrogen. If another sample was analyzed and
  found to contain 24.0 g of hydrogen, how many
  grams of carbon would it contain?

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CONSERVATION OF MASS

• Law of conservation of mass mass is neither
  created or destroyed during a reaction.
• The atoms form new bonds and thus are present
  after reaction only bound to some other atoms.
• E.g. 2H2(g) O2(g) ? 2H2O(l) 2 g of H2 plus 16
  g of O2 produce how many grams of water?

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Properties of Matter

• Physical properties that can be measured without
  changing the chemical composition of the
  substance E.g. melting point, smell, density.
• Chemical properties that described a substances
  reactivity. E.g. Alkali metals react to form
  positively charge substances halogens form
  negatively charged substances
• Intensive physical or chemical property that
  does not depend upon the amount of the substance.
  Temperature, density, etc.
• Extensive physical or chemical property that
  depends upon the amount of material. E.g. two
  tanks of propane produce twice as much heat when
  burned as one tank.

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Units of Measurement

• Mass, temperature and volume are commonly
  measured in the lab.
• SI (System International) internationally
  accepted measurement system for measuring Mass,
  length, temperature, etc.
• Basic Units
• Mass measured in grams tells how much of an
  object there is related to weight, which is the
  gravitational pull on the object.
• Length measured in meters
• Temperature measured in K or C. Each is based
  upon the same reference temperatures freezing
  and boiling point of water.
• Conversion from one scale to the other based upon
  change in height of mercury between two
  temperatures. i.e. ?h ki?Ti
• E.g. what is the temperature in the centigrade
  scale if it is 44F?

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Temperature Conversions

• Conversion between
• temperature scales use
• Where DTa,ref Tb,a Tf,a and DTa Ta Tf,a
• E.g. Determine the temperature in the centigrade
  scale corresponding to 76F.

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Units of Measurement(contd)

• Prefixes make it possible to express measurements
  in a more convenient manner.
• Derived Units
• Speed distance per elapsed time m/s
• Volume m3 volume often expressed in liter (L)
• Density mass per volume, g/m3
• E.g. 100 g of table salt occupies 46.2 g. What
  is its density?
• E.g.2 The density of liquid bromine is 3.12
  g/mL. What is the mass of 150 mL of bromine?

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Dimensional Analysis

• Often necessary to convert from one type of unit
  to another.
• The method of dimensional analysis is used
• Multiply original number by conversion factors
  which change from one unit to another.
• Conversion factor is the relationship between two
  units.
• Can involve derived units.
• Determine
• ? micrometers in 100 pm
• ? ng in 55x10?5 kg
• ? kg/m3 in 3.45 g/mL
• ? pm2 in 6.22x10?6 cm2
• ? Mm in 256000 m

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SIGNIFICANT FIGURES

• All measurement made at a certain level of
  uncertainty and are often made several times to
  reduce it.
• Precision closeness of measured values.
• Accuracy closeness of measured value to the
  correct answer.
• Significant figures in reported measurement
  indicate its precision. Rules
• Numbers (except zeroes) at beginning of the
  number sequence are significant.
• Zeroes at the end of the number and to the right
  of the decimal point are significant.
• Zeroes at the end of the number and to the left
  of the decimal point are not necessarily
  significant.
• Avoid ambiguities by expressing in scientific
  notation Ax10a where A is a number between 1 and
  9.999 and a is an integer.
• Exact numbers are known to an infinite number of
  significant figures.

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SIG FIG AND CALCULATIONS

• Results of measurements often used to calculate
  some number. How many significant figures (sig
  fig) should the resulting number have?
• Rules
• Addition and subtraction of numbers Add all
  numbers express to same number decimal places as
  the original number with the least number of sig.
  figs.
• Multiplication and division of numbers Do
  calculation and then round to same number of sig
  figs as the number with least number of sig fig.

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ROUNDING

• Rounding up or down is required to obtain correct
  number of significant figures.
• Rules If the number immediately after the last
  digit to be saved is
• gt5 round up (add 1 to previous digit).
• lt5 round down (drop number).
• 5 round up if the last digit to be saved is an
  odd number round down if even.
• E.g.1 Round each to three significant figures
  0.2226, 0.22225, 5555, 554523
• E.g. 2 Express the following in the correct
  number of significant figures
• 10000.0 ? 3.14159
• 142.7 0.081
• 6.246 8.139 ? 12.75
• 19.69 ? 0.041 1.27

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Basic Math (see appendix)

• Essential to know HS Algebra II well!
• Multiplication of two numbers add the exponents
  for the powers of ten and multiply the two
  numbers together. Solve
• 2.5x105?2.0x10?5 .
• Powers and roots For (Ax10n)m raise A to the m
  power and multiply n by m
• Solve (2.11x105)3
• Log and antilog(natural and base ten)remember
  the definition of a logarithm log x z where x
  10z. The antilog of z in the example would be
  x .
• log xy log x log y
• Proportionalities
• Linear- y mx b P kT
• Squared - y mx2 b R kA2 (second
  order reaction)
• Inverse -

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Basic Math Problems

• Eg. The pressure of a gas was 1.00 atm. at 273 K.
  What was the pressure at 373 K?
• E.g. 2 The rate of a second order reaction was
  2.50x10-2 s-1 when the concentration was 0.100 M.
  What would the rate be when the concentration is
  0.250 M?
• E.g. 3 A gas occupied a volume of 12.5 L when the
  pressure was 2.00 atm. What volume would it
  occupy if the pressure increased to 3.75 atm?