CHEM 112 week 4 notes
CHEM 112 week 4 notes CHEM 112000
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This 3 page Class Notes was uploaded by Olivia Lee on Monday February 1, 2016. The Class Notes belongs to CHEM 112000 at Purdue University taught by Abu-Omar in Winter 2016. Since its upload, it has received 9 views. For similar materials see Chemistry in Chemistry at Purdue University.
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Date Created: 02/01/16
nd CHEM 112 1 Edition Lecture 4 Outline of Last Lecture I. Ideal Gas Law II. Dalton’s Law III. Kinetic-Molecular Theory of Gasses Outline of Current Lecture I. Liquid-Gas Phase Changes II. Boiling Point III. Liquid-Solid Phase Changes IV. Solid-Gas Phase Changes V. Heating & Cooling Curves Current Lecture Liquid-Gas Phase Changes o Evaporation or vaporization Evaporation occurs because some surface liquid molecules have high enough kinetic energy to escape to the gas phase. Heat is required to maintain the temperature needed for evaporation Endothermic Does not break bonds, just changes physical state o Condensation Transition from a gas phase to a liquid Occurs when gas particles cannot escape the container and this, come into contact with a liquid An exothermic process These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. o Equilibrium: a state in which opposing processes occur at equal rates. o Liquid-Vapor Equilibrium A liquid placed in a closed container will evaporate only until equilibrium is reached. The pressure exerted by the vapor at equilibrium is the vapor pressure. Boiling Point o Boiling occurs when the vapor pressure equals the external pressure of the atmosphere o The temperature at which vapor pressure equals the external pressure of the atmosphere is the boiling point o If the external pressure is exactly 1 atm, the boiling temperature is called the normal boiling point ACTIVITY Consider the vapor pressure curve for propane to the left, which is used as a fuel in barbeque grills. What is the normal boiling point for propane? o Around -48 degrees Celcius (look at where the graph equals 1 atm) Liquid-Solid Phase Changes o Temperature which the liquid and solid states coexist in equilibrium called the freezing point or the melting point Solid-Gas Phase Changes o Under certain conditions, substances can go directly from the solid state to the gas state: sublimation. CO2 and I2 do this under normal conditions. o Deposition is a direct transition from gas to solid. Reverse of sublimation. Cooling and Heating Curves o Show the phase changes of a substance as heat is removed or added at a constant pressure o Cooling curve: heat it removed o Heating Curve: heat is added
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