CHE 101 Lecture Notes - Lecture 2: Chemical Industry, Middle Ages
11 Jun 2018
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Early Models of the Atom
The earliest suggestion that atoms might exist came in the 5th century BC we=hen
Democritus expanded on the ideas of his teacher and stated that the differences between
substances were the direct result of differences in the size and shape of tiny, uniform,
uncuttable particles.
In the 4th century BC, Aristotle rejected this idea and proposed that earthly matter had no
properties itself and that various combinations of simple properties existed in this
undifferentiated matter to create every substance known. The four properties which could
exist were moist, dry, heat and cold.
Aristotle’s theories of matter and properties were meant as philosophical analogies and were
not intended to suggest that one could actually extract and purify the properties from a
substance.
Some later versions of Aristotle’s theory stated that matter could be infinitely subdivided and
other versions stated that a non dividable smallest particle of each type of substance existed.
The important point to note is that all the Greek theories were essentially philosophical and
moralistic in nature and did little or nothing to suggest a direction for experimental work.
During the middle ages, a great deal of particle chemical knowledge accumulated from the
investigations of Arab and European alchemists. This large body of experimental work
contained information on the separation of metals from Oreos and numerous types of
distillations. From this body of work the idea that matter existed as corpuscles which were
subject to various attractions and repulsions eventually emerged, but again the ideas were
mainly philosophical in nature. So little chemical knowledge existed that there was no
chemical industry as such and little day to day usage of any chemicals other than those which
existed naturally in the form of food or beverages.
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Document Summary
The earliest suggestion that atoms might exist came in the 5th century bc we=hen. Democritus expanded on the ideas of his teacher and stated that the differences between substances were the direct result of differences in the size and shape of tiny, uniform, uncuttable particles. In the 4th century bc, aristotle rejected this idea and proposed that earthly matter had no properties itself and that various combinations of simple properties existed in this undifferentiated matter to create every substance known. The four properties which could exist were moist, dry, heat and cold. Aristotle"s theories of matter and properties were meant as philosophical analogies and were not intended to suggest that one could actually extract and purify the properties from a substance. Some later versions of aristotle"s theory stated that matter could be infinitely subdivided and other versions stated that a non dividable smallest particle of each type of substance existed.
