Chemistry 141 Monday, December 4, 2017 Lecture 36 Real Gases and Chemistry 11 - Lecture 11 9/30/2009 Chemistry 141 Monday, December 4, 2017 Lecture 36 Real Gases and Intermolecular Forces

Questions for today: How do gases flow from one region to another? How do real gases behave differently from ideal gases? How do solids and liquids differ in behavior from gases? What are the reasons for these differences? What are the forces that hold molecules together in solids and liquids? How do these interactions relate to the physical properties of substances?

Distribution of speeds

Speed vs. molecular mass

Effusion & Diffusion Effusion is the escape of gas molecules through a tiny hole into an evacuated space. Diffusion is the spread of one substance throughout a space or a second substance.

Principles of Kinetic Molecular Theory A gas is many small particles in constant, linear motion. The majority of the volume of a gaseous substance is empty space. Particles collide with each other and with the walls of the container. Intermolecular forces are negligible, other than collisions. Total kinetic energy remains constant, though individual particles may gain or lose energy via collisions.

Real Gases

States of matter

Intermolecular interactions dipole-dipole interactions induced dipole interactions

Trends in dispersion forces Higher MW leads to higher polarizability, stronger IM forces, and higher boiling points.

Trends in BP

Comparing IM forces

Viscosities

Phase changes

Heating curves