1. The Kinetic-Molecular Theory of Matter (Gases)
Chapter 10
Section 1

2. Behavior of Particles
Kinetic-molecular theory: a theory that explains the behavior of systems based on the idea that particles of matter are always in motion
Explains properties of matter in terms of the energy of the particles and the forces that act between them

3. Kinetic-Molecular Theory of Gases
The theory provides a model for an ideal gas
Ideal gas: a hypothetical gas that perfectly fits all the assumptions of the kinetic-molecular theory
Real gas: a gas that does not behave completely according to the assumptions of the kinetic-molecular theory

4. Five Assumptions
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
Elastic collision: one in which there is no net loss of total kinetic energy (energy is not transferred between the particles)

5. Elastic Collision

6. Assumptions
Gas particles are in continuous, rapid, random motion. They therefore possess kinetic energy
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

7. Random Motion of Gases

8. Physical Properties Expansion
Gas particles move rapidly in all directions with no attraction
This explains why gases do not have a definite shape or volume
They completely fill the container and take its shape

9. Fluidity
The ability of particles of a substance to move past one another.
Gas particles slip and slide past each other easily.
They flow like liquids.
Both liquids and gases are referred to as fluids.
Demo here with candle and alka-seltzer

10. Low Density and High Compressibility
The particles are very far apart from each other
Very low density (D = m/V)
The gas particles can be crowded closer together
The volume can be greatly decreased by compressing the gas

11. Diffusion
Diffusion: spontaneous mixing of the particles of two substances caused by their random motion
Gases spread out without being stirred or agitated.
The gas particles will naturally move throughout the available volume.

13. Effusion
Effusion: a process by which gas particles pass through a tiny opening
An example of this would be the air coming out of a leak in a car tire.
Molecules of low mass effuse faster than molecules of high mass (the “lighter” molecules move faster)

14. Deviations of Real Gases from Ideal Behavior
All real gases deviate from ideal behavior to some extent.
At very high pressure and low temperatures, when compared to “normal” conditions, real gases are least likely to behave ideally.

15. Non-ideal Behavior
Gases whose particles have low attraction for each other, like the noble gases, behave closest to ideal behavior. These are nonpolar elements and compounds.
The more polar the molecule of gas, the less likely it is to behave ideally.