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Do Now: packet page __ Relationship between Temp and Average Kinetic Energy. TOPIC: Kinetic-Molecular Theory (KMT). Models. Scientists use models because simpler than real life Kinetic-molecular theory can be extended to all phases of matter.
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Do Now: packet page __ Relationship between Temp and Average Kinetic Energy TOPIC: Kinetic-Molecular Theory (KMT)
Models • Scientists use models because simpler than real life • Kinetic-molecular theory can be extended to all phases of matter
Kinetic-Molecular Theory (KMT) as it pertains to ideal gases There are 4 assumptions to the KMT
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
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
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
3) Gas molecules separated by such great distances that the volume of molecule is negligible (not significant) • Ideal gasses are considered not to have volume, but they still have a mass, so scientists call this a point mass
Real gases do interact with one another…that’s why water vapor condenses… Intermolecular forces
Ideal vs Real • Real ( at high pressure & low temperature) • Particles take up space (they have volume) • All gas particles are subject to intermolecular interactions • Ideal • Particles themselves take up no space • Particles have no intermolecular forces
Example: N2(g) At a low temperature, the kinetic energy is… low, which means their intermolecular forces are strong enough to hold them together Nitrogen gas become liquid Nitrogen
Propane If you increase the pressure, the volume… decreases, which forces particles closer together. They will become a liquid
VIDEO LINK • http://ed.ted.com/lessons/describing-the-invisible-properties-of-gas-brian-bennett