How do scientists advance new knowledge?

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Introduction:
The two philosophers and 5 scientists pictured above were involved in advancing the theories related to atomic structure. Students from Gabe Cronin and Thomas Adam’s science class at Seattle Academy were tasked with understanding each scientist’s point of view, the experiments they conducted, and the implications of a shift from an existing theory to a newer theory. In all cases the shift happened because of direct experimental evidence which contradicted the previously held theory.

To demonstrate their findings students created audio podcasts which included three characters: a narrator and two debaters (scientists and/or philosophers). The podcasts can be found here:

http://atomic-structure.wikispaces.com/

Debate Pairs:

A. Aristotle vs. Einstein: Continuous Matter vs. Atoms

Aristotle was a Greek philosopher who believed that matter was infinitely divisible; atoms did not exist and matter could be sliced into finer and finer sections without limit. Einstein interpreted the results of Brown’s experiment on the motion of pollen to prove that atoms exist.

B. Aristotle vs. Dalton: Continuous Matter vs. Atoms

Aristotle was a Greek philosopher who believed that matter was infinitely divisible; atoms did not exist and matter could be sliced into finer and finer sections without limit. Dalton was an English schoolteacher who developed an atomic theory based upon three laws derived from experimental data; the Law of Multiple Proportions, the Law of Conservation of Mass, and the Law of Definite Composition.

C. Priestley vs. Lavoisier: Phlogiston Theory of Combustion (loss) vs. Oxidation Theory of Combustion (gain)

Priestley was a 18th century researcher who believed that objects release a substance called phlogistan when burned. Lavoisier was an 18th century tax-collector whose precise mass measurements proved that metals often gain mass when combusting, leading to the Law of Conservation of Mass.

D. Rutherford vs. Bohr: Electrons in Continuous Energy Levels vs. Electrons in Discrete Energy Levels

Ernest Rutherford’s 1909 experiment with alpha particles suggested that atoms contained a dense, small, positive nucleus with electrons orbiting in rings at any distance from the nucleus. Niels Bohr’s interpretation of spectral lines in the hydrogen atom suggested that electrons could only exist in specific energy levels corresponding to specific distances from the nucleus, and that electrons could perform quantum leaps to move from one energy level to another without ever occupying the space between.

E. Thomson vs. Rutherford: Plum Pudding Model vs. Planetary Model

Thomson’s work on the cathode ray tube suggested the existence of small, negatively charged electrons. His model for the atoms consisted of these electrons embedded in a dense, space-filling matrix of positive charge and was called the Plum Pudding model. Ernest Rutherford’s 1909 experiment with alpha particles suggested that atoms contained a dense, small, positive nucleus with electrons orbiting in rings at any distance from the nucleus, and that most of the atom was empty space.

F. Bohr vs. Modern Model: Rings vs. Clouds

Niels Bohr’s interpretation of spectral lines in the hydrogen atom suggested that electrons could only exist in specific energy levels corresponding to specific distances from the nucleus, and that electrons could perform quantum leaps to move from one energy level to another without ever occupying the space between. The modern model states that electron position and energy cannot both be specified, meaning that electron position is described by regions of space (clouds) where electrons are most likely to be found.

G. Dalton vs. Oppenheimer: Atoms are Indivisible vs. Atoms are Divisible

Dalton was an English schoolteacher who developed an atomic theory based upon three laws derived from experimental data; the Law of Multiple Proportions, the Law of Conservation of Mass, and the Law of Definite Composition. Oppenheimer was the head physicist for the Manhattan project, in which the atom was split to first the first atomics bombs dropped to end WWII.

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