Kinetic Theory of Matter.
المؤلف:
GEORGE A. HOADLEY
المصدر:
Essentials of Physics
الجزء والصفحة:
P-12
2025-10-18
282
According to the kinetic theory of the structure of matter, the molecules of all bodies are in rapid vibration and the three states which matter assumes may be considered as resulting from the kind of motion of the molecules and their relative velocities.
In solids the motion of the molecule is restricted to a limited space, and although it is in constant vibration, its position with respect to the other molecules of the body is relatively fixed. Hence the shape of a rigid solid, under normal conditions of pressure and temperature, is unchanged.
In liquids the molecule is free to move in any direction. This means that the molecules of a liquid will glide over one another, and that the liquid will take the shape of any vessel into which it is poured.
In gases the molecule has a high velocity, moving in a straight-line path until it comes in contact with some other molecule or with the walls of the containing vessel. On account of this high molecular velocity a gas cannot be kept in an open vessel, and however small the quantity of gas, it will always fill any vessel in which it is confined. The quantity of gas in a closed vessel determines the pressure it will exert upon the walls.
Some substances assume all three states through a change of temperature alone, as water, which may be solid (ice), liquid (water) and gaseous (invisible vapor). Others require a change of pressure as well as a change of temperature.
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