Ch. 10 - States of Matter

The kinetic-molecular theory is based on the idea that particles of matter are always in motion.

The theory can be used to explain the properties of solids, liquids, and gases in terms of the energy of particles and the forces that act between them.

Gases consist of large numbers of tiny particles that are far apart relative to their size. 

Collisions between gas particles and between particles and container walls are elastic collisions.

Gas particles are in continuous, rapid, random motion. They therefore possess kinetic energy, which is energy of motion. 

There are no forces of attraction between gas particles.

The temperature of a gas depends on the average kinetic energy of the particles of the gas. 

An ideal gas is a hypothetical gas

that perfectly fits all the assumptions of the kinetic-molecular theory.

An elastic collision is one in which there is no net loss of total kinetic energy.

A real gas is a gas that does not behave completely according to the

assumptions of the kinetic-molecular theory.

Expansion

Gases do not have a definite shape or a definite volume. They completely fill any container in which they are enclosed, and they take its shape.

Fluidity

Because the attractive forces between gas particles are insignificant, gas particles glide easily past one another. Because liquids and gases flow, they are both referred to as fluids.

Low Density

The density of a gaseous substance at atmospheric pressure is about 1/1000 the density of the same substance in the liquid or solid state.

Compressibility

During compression, the gas particles, which are initially very far apart, are crowded closer together. The volume of a given

sample of a gas can be greatly decreased.

Gases spread out and mix with one another, even without being stirred. Such spontaneous mixing of the particles of two substances caused by their random motion is called diffusion.

In contrast, effusion is a process by which gas particles pass through a tiny opening. 

 The pressure exerted by a gas depends on volume, temperature, and the number of molecules present.

Pressure (P) is defined as the force per unit area on a surface.

The SI unit for force is the newton, (N). It is the force that will increase the speed of a one-kilogram mass by one meter per second each second that the force is applied.