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 Random, straight-line? - 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?