Gases, Liquids and Solids
Objectives
Defines heat and temperature
Looks at changes of state
Introduces the kinetic molecular theory of matter
Discusses the gas laws and the idea of vapour pressure
Shows how to use the ideal gas equation in calculations
Although people have always recognized the distinction between liquids and solids,
the idea of a gas as we know it today only began to develop in the 1760s. The absence
of such a concept severely hindered chemists in their attempt to make sense of the
burning of fuels and of the tarnishing of metals in air, both of which we now know to
be chemical reactions involving gaseous oxygen.
Heat and temperature
The hotness or coldness of an object is measured by its temperature(Box 10.1). If we
make an object hot, we have transferred energy to that object. This energy is called
heat.
Changes in the state of matter
Everyday observations show that solids have a definite shape and volume. Liquids
possess the shape of their container but their volume is fixed and does not depend
upon the volume of their container. Gases take up the shape and volume of their
container (Fig. 10.2(a)).
Kinetic molecular theory of matter
The idea that matter consists of moving particles (molecules, atoms or ions) is
the basis of the kinetic molecular theory(or simply, kinetic theory). Its two main
assumptions are:
10.2
10.1
Contents
10.1Heat and
temperature 15310.2Changes in the state
of matter 15310.3Gas laws 15710.4Kinetic molecular
theory of gases 16110.5Ideal gas equation 16210.6Adsorption of gases
on solids 16410.7Vapour pressure 16510.8Critical temperature
and pressure 16810.8Revision questions 16910
UNIT