States of Matter and Intermolecular Forces

3 Phases of Matter Solid Solid Liquid Liquid Gas Gas

How do particles move in a solid?

Solids Have a definite shape/structure Have a definite shape/structure Very little particle movement—fixed position Very little particle movement—fixed position

Liquids Limited structure to particles Limited structure to particles Movement is less restricted, particles can move around and collide with each other Movement is less restricted, particles can move around and collide with each other Conform to a container’s shape Conform to a container’s shape

Gases No structure No structure Movement is not restricted Movement is not restricted Particles are always in motion Particles are always in motion Expansion occurs Expansion occurs

Phase Changes Physical change of a chemical compound Physical change of a chemical compound Change of state Change of state Types: Types: Melting Melting Freezing Freezing Vaporization Vaporization Condensation Condensation Sublimation Sublimation Deposition Deposition

Evaporation/Vaporization Liquid---gas, endothermic Liquid---gas, endothermic Liquid molecules gain enough energy to enter the gaseous state via breaking intermolecular forces. Liquid molecules gain enough energy to enter the gaseous state via breaking intermolecular forces. Enthalpy of vaporization— Enthalpy of vaporization— Amount of heat necessary to evaporate a liquid at constant temperature Amount of heat necessary to evaporate a liquid at constant temperature kJ/mole kJ/mole Table 11.1 (p. 435) Table 11.1 (p. 435)

Condensation Gas-----liquid Gas-----liquid Exothermic process Exothermic process

Example 1 At 25°C, how much heat is required to evaporate 175 g of methanol?

Example 2: Which liquid in Table 11.1 (p. 435) requires the lowest amount of heat for vaporization?

Homework Test Study Guide Test Study Guide

Vaporization/Condensatio n Processes exist at the same time Processes exist at the same time Dynamic equilibrium is established Dynamic equilibrium is established Rate of vaporization = rate of condensation Rate of vaporization = rate of condensation No net change in molecular movement No net change in molecular movement Many factors determine how long it will take for equilibrium to be established Many factors determine how long it will take for equilibrium to be established

Vapor Pressure Characteristic of liquid Characteristic of liquid Partial pressure of vapor when it exists with a liquid in dynamic equilibrium under constant temperature Partial pressure of vapor when it exists with a liquid in dynamic equilibrium under constant temperature Dependent on liquid type and temperature at equilibrium Dependent on liquid type and temperature at equilibrium INCREASE vapor pressure of liquid, INCREASE temperature INCREASE vapor pressure of liquid, INCREASE temperature

Vapor Pressure Curve Figure 11.4 p. 439 Figure 11.4 p. 439

Volatile vs. Nonvolatile Liquids 1)Volatile Liquids WEAK intermolecular forces WEAK intermolecular forces High vapor pressure High vapor pressure Ex. Gasoline, alcohols, “Whoosh Bottle” Ex. Gasoline, alcohols, “Whoosh Bottle” 2)Nonvolatile Liquids STRONG intermolecular forces STRONG intermolecular forces Low vapor pressure Low vapor pressure

Whoosh Bottle Demo Video

Boiling Point Liquid characteristic Liquid characteristic Vaporization present throughout the liquid Vaporization present throughout the liquid Point where vapor pressure = atmospheric pressure Point where vapor pressure = atmospheric pressure Aids in liquid identification Aids in liquid identification Decrease atmospheric pressure with increased altitude, lowers boiling point Decrease atmospheric pressure with increased altitude, lowers boiling point

Boiling Point (cont.) Critical temperature/pressure (T C, P C ) Critical temperature/pressure (T C, P C ) Highest temperature with liquid and vapor present as physically different states in equilibrium Highest temperature with liquid and vapor present as physically different states in equilibrium Point where increased pressure only will result in condensation Point where increased pressure only will result in condensation Critical Point Critical Point Actual physical condition where critical temperature and pressure achieved Actual physical condition where critical temperature and pressure achieved

Melting/Melting Point Melting/freezing point Melting/freezing point Temperature when solid “melts” Temperature when solid “melts” Temperature when liquid becomes solid Temperature when liquid becomes solid For water = _________ For water = _________ Enthalpy (heat) of fusion– Δh fusion Enthalpy (heat) of fusion– Δh fusion Amount of heat needed to convert a certain amount of a solid to a liquid Amount of heat needed to convert a certain amount of a solid to a liquid Melting—endothermic Melting—endothermic Freezing—exothermic (- value) Freezing—exothermic (- value)

Cooling/Heating Curves Figure 11.7 p. 444 Figure 11.7 p. 444

Sublimation Solid  Gas Solid  Gas Some solid compounds are volatile enough to have a vapor pressure and convert to gas Some solid compounds are volatile enough to have a vapor pressure and convert to gas Ex. Mothballs, dry ice Ex. Mothballs, dry ice Rate of sublimation = rate of deposition Rate of sublimation = rate of deposition Sublimation curve Sublimation curve Sublimation pressure— Sublimation pressure— Pressure of a vapor existing in equilibrium with a solid Pressure of a vapor existing in equilibrium with a solid

Enthalpy (heat) of sublimation = ΔH fusion + ΔH vapn = ΔH fusion + ΔH vapn

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