Chem 123 Notes

Chem 123 Notes - Stephanie Long Chapter 12: Liquids, Solids...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Stephanie Long Chapter 12: Liquids, Solids and I ntermolecular Forces 12-1 I ntermolecular Forces and Some Properties of Liquids- Surface tension decreases with increased temperature. Why? o Increase of temperature increases the intensity of the molecular motion, which causes the intermolecular forces become less effective o Thus, less work is required to extend the surface of a liquid 12-2 Vaporization of Liquids: Vapor Pressure- Vaporization occurs more readily with: o increased temperature o increased surface area of the liquid-- a greater proportion of liquid molecules are at the surface o decreased strength of intermolecular forces-- kinetic energy needed to overcome intermolecular forces of attraction is less- Enthalpy of Vaporization: o Molecules lost through evaporation are much more energetic than average average kinetic energy of the other molecules decreases o Causing the temperature of the evaporating liquid to fall o To vaporize a liquid at a constant temperature, the lost kinetic energy must be replaced by adding heat to the liquid o Called: enthalpy of vaporization is the quantity of heat that must be absorbed if a certain quantity of liquid is vaporized at a constant temperature 1 Stephanie Long H vaporization = vapor - liquid o Vaporization is ENDOTHERMIC, H vaporization is ALWAYS POSITIVE o Conversion of gas or vapor to liquid is CONDENSATION H condensation = liquid - vapor = - H vaporization ALWAYS NEGATIVE EXOTHERMIC- Vapor Pressure o Dynamic equilibrium always implies that two opposing processes are occurring simultaneously and at equal rates No net change with time once equilibrium has been established o Vapor pressure- pressure exerted by a vapor in dynamic equilibrium o Volatile- liquids with high vapor pressures at room temperature o Nonvolatile- very low vapor pressures at room temperature o The weaker the intermolecular forces, the more volatile the liquid (the higher the vapor pressure) o Vapor pressure depends on the particular liquid and temperature, NOT ON amount of liquid or vapor (as long as some of each is present at equilibrium)- Boiling and the Boiling Point 2 Stephanie Long o During boiling, energy absorbed as heat is used only to convert molecules of liquid to vapor o Temperature remains constant unt il all liquid has boiled away o Normal boiling point is the boiling point of a liquid at 1 atm pressure- The Critical Point o If a liquid is heated in a sealed container, boiling doesnt occur, instead the temperature and vapor pressure rise continuously o If the right quantity of liquid is sealed in a glass tube and heated, this can be observed: Density of liquid decreases, density of vapor increases, eventually two densities become equal Surface tension of the liquid approaches zero, interface between the liquid and vapor becomes less distinct and eventually disappears o Temperature at critical point is critical temperature o Pressure at critical point is critical pressure...
View Full Document

This note was uploaded on 07/11/2010 for the course CHEM CHEM 123 taught by Professor Oakley during the Winter '08 term at Waterloo.

Page1 / 17

Chem 123 Notes - Stephanie Long Chapter 12: Liquids, Solids...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online