Ch. 10 - States of Matter

Ch. 10 - States of Matter

Ch. 11 - Gases

The Kinetic-Molecular

Theory 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.

Multiple Select

The kinetic-molecular theory is based on

• Particles of matter are always in motion.

• Particles of matter are always at rest.

• Particles of matter are always forming molecules

The Kinetic-Molecular

Theory of Gases

• 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. 

Key Terms

• 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.

Multiple Choice

The temperature of a gas depends on the average static energy of the

particles of the gas.

• True

• False

Physical Properties of Gases

• 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.

Physical Properties of Gases

• 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. 

Ch. 11 - Gases

you will learn about

other properties of gases, including pressure, volume, and amount of gas

present, and the relationship between these properties.

Pressure

•  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. 

Gas Pressure

If you pump air into an automobile tire, the pressure in the tire will increase. The pressure increase is caused by the increase in the number of collisions of molecules of air with the inside walls of the tire. The collisions cause an outward push, or force, against the inside walls. 

Conversion factors

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