1. Kinetic-Molecular Theory

2. Models Scientists use models because simpler than real life
Kinetic-molecular theory can be extended to all phases of matter

3. Kinetic-Molecular Theory (KMT)
Lets discuss how pertains to gases:
There are 4 assumptions to the KMT

4. 1) Gases consist of spherical molecules moving in constant, random, straight- line motion
- move in straight lines until hit something, then can bounce off at any angle

5. Kinetic-Molecular Theory
2) Gas particles undergo “elastic” collisions with each other and with walls of container
“Elastic” means total KE is conserved
KE does not get converted to heat or sound or any other kind of energy
KE can be transferred between particles

6. Kinetic-Molecular Theory
3) Gas molecules separated by great distances that volume of molecule is negligible
distance between molecules is more important than actual size of molecule

7. Kinetic-Molecular Theory
4) Gas molecules do not attract or repel each other
Assume there are no interactions between gas molecules

8. Real vs. ideal gas Ideal gas obeys assumptions of KMT all the time
It’s a model
It doesn’t exist
Real gases follow KMT most of time, but not at high pressure & low temperature
KMT breaks down when molecules are close together

9. Review of KMT
What features of the Kinetic- Molecular model are close to real gases?
What features of the Kinetic- Molecular model break down?
low pressure & high temperature
high pressure & low temperature