Man's physical universe

xanabras

UNIT IV

SECTION 5

PHYSICAL PROPERTIES AND PHYSICAL PROCESSES ARE

EXPLAINED BY THE KINETIC-MOLECULAR THEORY

Introduction.

The properties of gases, liquids, and solids and the physical processes

by which matter changes from one state to another are generally

accepted without question. No one doubts the correctness of Boyle's

Law, Graham's Law, and Charles' Law, although it is recognized that

they are not exact laws but approximations only. It was not until the

kinetic-molecular theory was evolved that man was able satisfactorily

to explain the properties of gases, liquids, and solids and understand

the laws dealing with physical changes.

The kinetic-molecular theory is one of the great theories of physical

science. For that reason it is important that we pause here to study

this theory and see how beautifully it explains so many phenomena and

aids in the prediction of the outcome of the untried experiments.

Turn to Unit I, Section 3, and review the portion dealing with the

nature and function of theories.

Many Men Contributed to the Development of the Kinetic-molecular

Theory.

Sir Francis Bacon (1561-1626), impressed by the failure of scholasticism

to advance knowledge, advocated the use of a more scientific

method. His method of attack involved extensive observations, recording

of available observations, carrying out experiments suggested by

these observations as far as possible, and then formulating general laws

which show the relationships between these observations.

In experimenting with a pan filled with sand. Bacon observed that

heavy particles rested on the surface of the sand when the pan was at

rest. As soon, however, as the sand was shaken, the heavier particles

worked their way to the bottom; in other words, the sand behaved

very much as a liquid in its inability to support a body more dense

than itself.

Bacon, himself, accomplished little in actual experimental work, but

the method he advocated is said to have influenced Robert Boyle.

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