General Chemistry Course Goals

1
Chem 1a Lecture 2 Chemistry Objective Composition
of Matter Methods of Discovery Conservation
Laws Leading to Atomic Theory Daltons Atomic
Theory
Authored by Fred J. Grieman
2
Chemistry - What is it?

Math Physics
Biology Geology
Chemistry

• Study of Matter What it is, How it Changes,
  Energy Involved
• How?
• Think of Chemiluminescence Demonstration
• Observation 2) Description 3) Ask ?s 4)
  Answer ?s
• 5) New ?s 6) Better Understanding
• Types of ?s
• What? Qualitative
• How much? Quantitative
• Why? Fundamental
• Purpose?
• Practical - To make and use matter to live and
  live better
• Philosophical - Why are things the way they
  are?

3

• Objective Concrete Results that We Can Ponder
• Empirical Law Quantitative relationship between
  measured quantities
• determined by experiment
• (Publish - Name in Author Index)
• 2) Theory ? Model which unifies a set of
  empirical laws often proposing quantities
• that cant be measured directly.
• ? A theory predicts and encompasses large
  numbers of empirical laws
• the more, the more fundamental
• (Publish - Name in SUBJECT Index)

Composition of Matter Substance material -
cant separate into 2 materials w/ different
properties
by ordinary PHYSICAL means 2 Kinds - What
are they? Element cant be broken down to
other substances by ordinary CHEMICAL means The
building blocks only 113!!!
Amazing! Periodic Table symbol Know 1st 10
(Name Symbol) by next week, 1st 20 by
following week 1st 36 by end of
semester
4
Compound Composed of 2 Elements in definite
proportion by mass Different Prep.
always gives the same proportion Combination of
Substances in Various Amounts MIXTURE 2
Types. What are they? Homogeneous - same
throughout example ?
solutions like
alcohol water physical
properties vary (like boiling point Tbp(eth)
78.5?C) physically
separate? Can
use different
physical properties distillation
Heterogeneous - non-uniform
example? Iron ore - magnetite Fe2O3 FeO
mixture Blast Furnace Fe2O3 3 CO ? 2 Fe
3 CO2
?
5
Determination of Components of Substance or
Mixture Analysis (Taking Apart) A lot in
Chem 1 lab! H2O e.g. Chloride Salts MCl ?
M(aq) Cl-(aq) Cl-(aq) Ag(aq)
? AgCl(s) (measure mass) Synthesis
(combination of substances to make new
substance(s) Chem 1 Lab too!
Microscopic World Atomic Theory Modern times
mass spec, spectroscopy, electron microscope
direct evidence
CLOCK WORKS. When installed in an atomic clock,
this molybdenum structure (left) traps a mercury
ion (right, arrow) at its center. The clock uses
the ion to keep time with unprecedented
precision. (Bergquist and D. Wineland/NIST)
6

• Leading to Daltons Atomic Theory
• Why Look at This?
• Appreciation History Still Use these
  Techniques Learn how to Reason
• Conservation of Mass (Lavoisier)
• S Mass(reactants) S Mass(products)
• Beginning of Chemistry as Algebraic
  Equations !!!
• Importance of Balance in Chem 1 Lab !!!
• 2) Law of Definite Proportions (Proust)
• Compound proportion of masses of elements
  are FIXED
• 100 g AB ? 75 g A 25 g B 3/1
• 200 g AB ? 150 g A 50 g B 3/1
• Does this mean there must be atoms??

7

• Daltons Atomic Theory
• Discrete, indivisible atoms exist
• Atoms of an element have identical properties
  mass
• Different elements have different properties
  mass
• Atoms are indestructible in chemical reactions

There are two ways scientists have seen that
atoms are divisible in spontaneous radioactive
decay (for example with all isotopes of uranium
or radium) and in "atom smashing" events, for
example in a nuclear reactor. Isotopes were not
discovered until almost 100 years after Dalton's
work. Isotopes have virtually identical chemical
properties but have different masses. It is
still true that there are no instances where
atoms are destroyed in a chemical reaction. Atoms
are destroyed in nuclear reactions Some solid
compounds in fact do have fractional elemental
composition. A few of these were known in
Dalton's time, but experimental imprecision
prevented their recognition.
Next Time Atomic Theory and Chemical Writing
(Formulas)