ConcepTest At a certain temperature the largest number of oxygen molecules have a velocity of ca 370 m s while the similar velocity for helium is 1200 m s Which gas has more molecules at 1500 m s A oxygen KE mv2 B helium 2 190 400 C both have the same D not enough info given 20 160 000 Evidence from Boyles Law As V decreases molecular collisions with walls increases and P increases Daltons Law Gases have few intermolecular attractions pressures are independent Charles Law Increase in temp raises velocities V increases to keep P constant Diffusion Spreading and intermingling of gases Due to random molecular motion Effusion The escape of gas through small openings What happens to the energy when a molecule collides with something Think of billiards table Balls are ceramic and are meant to emulate inelastic collisions no energy lost Same premise no energy lost when they bounce off each other Which best describes the loss of helium from a balloon overnight A Charles s Law B effusion D Conservation of mass C diffusion E none of these ConcepTest For which gas would you predict the largest non ideal increase in pressure due to intermolecular forces A He B Cl2 C H2O D Ar E H2 F CO2 P n2a V2 V nb nRT Real vs Ideal Gases Variations from ideal Gases behave ideally at ambient temps and pressures At low temps and or high pressures gases don t behave ideally o Gases are very close to one another making their volume important can t assume no volume o Intermolecular interactions normally very small become important FINAL 4 multiple choice answers If calculation one choice may represent a common misconception