Kinetic-Molecular Theory (KMT)

Models scientists use models because simpler than real lifescientists use models because simpler than real life Kinetic-Molecular Theory can be extended to all phases of matterKinetic-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 random, straight-line? random, straight-line? - move in straight lines until hit something, then can bounce off at any angle - 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 “elastic” means total KE is conserved KE does not get converted to heat or sound or any other kind of energyKE does not get converted to heat or sound or any other kind of energy KE can be transferred between particlesKE 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 moleculedistance 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 moleculesassume there are no interactions between gas molecules

real vs. ideal gas ideal gas obeys assumptions of KMT all the timeideal gas obeys assumptions of KMT all the time this is a model; doesn’t existthis is a model; doesn’t exist real gases follow KMT most of timereal gases follow KMT most of time NOT at high pressure & low temperatureNOT at high pressure & low temperature KMT breaks down when molecules are close together

Review of KMT What features of the Kinetic- Molecular model show real gases behaving like ideal gases?What features of the Kinetic- Molecular model show real gases behaving like ideal gases? What features of the Kinetic- Molecular model break down?What features of the Kinetic- Molecular model break down? ______ pressure & ______ temperature LOW HIGH HIGHLOW