Physical Chemistry I (TKK-2246) 13/14 Semester 2 Instructor: Rama Oktavian Office Hr.: M.13-15, Tu , W , Th , F

Outlines 1. Condensed Phase 2. Properties of liquids 3. Thermal compression and 4. Thermal compressibility and Vapor pressure 4. Thermal compressibility and Vapor pressure

Condensed Phase The definition of “condensed” 1. reduced in volume, area, length, or scope; shortened: a condensed version of the book. 2. made denser, especially reduced from a gaseous to a liquid state. 3. thickened by distillation or evaporation; concentrated: condensed lemon juice.

Condensed Phase The definition of “condensed phase” Solid and Liquid are condensed phase because the particles are very close together. There are strong intermolecular forces

Condensed Phase The definition of “condensed phase” made denser, especially reduced from a gaseous to a liquid state.

Liquid state Structure of liquids

Liquid state Structure of liquids Substances that can flow are referred as fluids. Both gases and liquids are fluid

Liquid state Structure of liquids The particles that form a liquid are relatively close together, but not as close together as the particles in the corresponding solid. The particles in a liquid have more kinetic energy than the particles in the corresponding solid. As a result, the particles in a liquid move faster in terms of vibration, rotation, and translation. Because they are moving faster, the particles in the liquid occupy more space, and the liquid is less dense than the corresponding solid.

Liquid properties intermolecular forces will play a major role in explaining their physical properties. Thermal expansion Compressibility Vapor pressure

Liquid properties How to describe P-V-T relationship in liquid state? The dependence of the volume of a solid or liquid on temperature at constant pressure can be expressed by where : α is coefficient of thermal expansion V 0 is volume of liquid at 0 C t is temperatur in Celcius

Liquid properties How to describe P-V-T relationship in liquid state? V 0 is function of pressure and expressed as where : is volume of liquid at 0 C and 1 atm V 0 is volume of liquid at 0 C is coefficient of compressibility

Liquid properties General definition of and Equation of state for liquid V = V(p,T) Take the partial derivative

Liquid properties General definition of and Volume expansivity Isothermal compressibility EoS for liquid can be written as:

Liquid properties General definition of and Volume expansivity Isothermal compressibility The value is usually small

Liquid properties General definition of and

Liquid properties The effect of pressure change to volume change of liquids If we take atm -1, then for a pressure of two atmospheres, the volume of the condensed phase is The decrease in volume in going from 1 atm to 2 atm pressure is % Liquid is incompressible fluid

Liquid properties EoS for liquids Find the volume change when acetone is changed from K and 1 bar to K and 10 bar

Liquid properties Other properties of liquid Viscosity Surface tension Vapor pressure

Liquid properties Viscosity the resistance of a liquid to flow Intensive property of liquids Viscosity depends on: - The attractive forces between molecules - Temperature - The viscosity of liquids decreases with increase the temperature

Liquid properties Effect of temperature M.A. Mehrabian, M. Khoramabadi, (2007) "Application of numerical methods to study the effect of variable fluid viscosity on the performance of plate heat exchangers", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 17 Iss: 1, pp

Liquid properties Surface tension the amount of energy required to increase the surface area of a liquid by a unit amount Stronger intermolecular forces cause higher surface tension Water has a high surface tension (H- bonding)

Liquid properties Surface tension

Liquid properties Phase change

Liquid properties Phase change Energy Changes Accompanying Phase Changes melting or fusion:ΔHfus> 0 (endothermic) vaporization:ΔHvap> 0 (endothermic) sublimation:ΔHsub> 0 (endothermic). deposition: ΔHdep < 0 (exo). condensation: ΔHcon < 0 (exo). freezing: ΔHfre < 0 (exo). The following sequence is endothermic: heat solid → melt → heat liquid → boil → heat gas The following sequence is exothermic: cool gas → condense → cool liquid → freeze → cool solid

Liquid properties Heating curve

Liquid properties Vapor pressure the pressure exerted by its vapor when the liquid and vapor are in dynamic equilibrium Vapor pressure Dynamic equilibrium is a condition in which two opposing processes occur simultaneously at equal rates Some of the molecules on the surface of a liquid have enough energy to escape the attraction of the bulk liquid. These molecules move into the gas phase. As the number of molecules in the gas phase increases, some of the gas phase molecules strike the surface and return to the liquid.

Liquid properties Vapor pressureVapor pressure as function of temperature

Liquid properties Evaporation vs boiling evaporation is a surface phenomenon - some molecules have enough kinetic energy to escape Boling point is the temperature at which the vapor pressure is equal to the external pressure, bubbles form

Liquid properties Normal boiling point The temperature at which the vapor pressure is equal to 1 atm

Solids Crystalline solid the units that make up the solid are arranged in a very regular, repeating pattern. Amorphous solid An amorphous solid lacks the long range order of a crystalline solid. Most plastics are amorphous solids. (they are polymers)

Solids Covalent Network Solids In a covalent network solid, all of the atoms in a crystal are held together by covalent bonds. Some examples of covalent network solids are diamond (C), boron nitride (BN), and silicon dioxide (SiO 2 ).

Solids Ionic Solids An ionic solid consists of oppositely charged ions, held together by strong electrostatic interactions. Binary compounds made up of a metal and a nonmetal are in this category. Example: NaCl

Problems EoS of liquids Express the volume expansivity and theisothermal compressibility as functions of density p and its partial derivatives For water at K (50°C) and 1 bar, K = x10-6 bar-1. To what pressure must water be compressed at K (50°C) to change its density by 1 %? Assume that K is independent of P.

Problems Castellan prob 5.7