KineticMolecular Theory KMT Models Scientists use models because
Kinetic-Molecular Theory (KMT)
Models • Scientists use models because they are simpler than real life • KMT (Kinetic-molecular theory) can be extended to all phases of matter
Kinetic-Molecular Theory 1) Gases consist of spherical molecules moving in constant, random, straight-line motion Random, straight-line? - move in straight lines until hit something, then they can bounce off at any angle
Kinetic-Molecular Theory 2) Gas particles undergo “elastic” collisions with each other and with walls of their 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 are separated by such great distances that volume of molecule itself is negligible • distance between molecules more important than actual molecule
Kinetic-Molecular Theory 4) Gas molecules do not attract or repel each other • Assume no interactions between gas molecules
Real vs. ideal gas • Ideal gas obeys all assumptions of KMT all the time • It’s a model • It doesn’t exist • Real gases follow KMT most of the time, but not at: high pressure & low temperature • KMT breaks down when molecules are close together
Review of KMT • What features of KMT model are close to real gases? • What features of the KMT model break down?
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