Greek Philosophers

1
Greek Philosophers

• Forerunners to todays scientists
• Purely driven by intellect and life experiences
  but very few controlled experiments
• Many believed matter was formed of 4 elements
  air, earth, fire and water
• Also believed matter could be endlessly divided
  into smaller and smaller units

2
Democritus

• Way ahead of his time in 400 B.C.
• Felt matter was not infinitely divisible
• Also felt matter could not be created or
  destroyed
• Conceived of the idea of atoms (atomos)
• Could not prove his idea without equipment
• Aristotle was a strong opponent so his ideas
  remained suppressed for 2000 years.

3
Democritus Theory

• Matter has empty space through which the atoms
  move
• Atoms are solid, homogeneous, indivisible (cant
  divide) and indestructible
• Different kinds of atoms differ in size and shape
• Changes in matter result from changes in the
  groupings of atoms not changes to the atom

4
John Dalton

• Agreed with Democritus on everything except the
  empty space idea.
• Had equipment available to prove his ideas
  (1800s).
• Refined a few of Democritus ideas.

5
Daltons Theory

• Atoms are solid, homogeneous, indestructible and
  indivisible
• Different kinds of atoms differ in size and shape
  also mass chemical properties
• Changes in matter result from changes in the
  groupings of atoms not changes to the atom in a
  reaction atoms are separated, then recombined or
  rearranged.
• Different atoms combine in simple whole number
  ratios to form compounds.

6
Modern Atomic Theory

• Atoms are solid, homogeneous, indestructible and
  indivisible can split atoms into smaller
  subatomic pieces (proton, neutron, electron)
• Different kinds of atoms differ in size and shape
  also mass chemical properties and atoms of
  the same element can differ in mass (isotopes)
• Changes in matter result from changes in the
  groupings of atoms not changes to the atom in a
  reaction atoms are separated, combined or
  rearranged.
• Different atom combine in simple whole number
  ratios to form compounds
• Matter is composed of empty space through which
  atoms move - much of an atom is empty space in
  which the electrons move

7
Alchemists

• They surfaced in the middle ages
• Main goal was to change a cheap metal into gold
  and produce an elixir that could give you eternal
  life
• Helped advance our understanding of matter by
  uncovering many properties of metals.