Kinetic-Molecular Theory (KMT)

Models Scientists use models because they are simpler than real lifeScientists use models because they are simpler than real life KMT (Kinetic-molecular theory) can be extended to all phases of matterKMT (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 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 are separated by such great distances that volume of molecule itself is negligible distance between molecules more importantdistance between molecules more important than actual molecule than actual molecule

Kinetic-Molecular Theory 4) Gas molecules do not attract or repel each other Assume no interactions between gas moleculesAssume 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 KMT model are close to real gases? What features of the KMT model break down?What features of the KMT model break down?