Kinetic-Molecular Theory

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

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

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

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

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

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

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

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