Chapter 11 Liquids, Solids, and Intermolecular Forces

Chapter 11 Liquids, Solids, and Intermolecular Forces
Chemistry: A Molecular Approach, 2nd Ed. Nivaldo Tro Chapter 11 Liquids, Solids, and Intermolecular Forces

Lesson 1 Solids, Liquids, and Gases: A Molecular Comparison
Tro: Chemistry: A Molecular Approach

Properties of the three Phases of Matter
___________ = keeps shape when placed in a container ___________ = takes the shape of the container Tro: Chemistry: A Molecular Approach, 2/e

Three Phases of Water Notice that the densities of ___________ are much larger than the density of _________ Notice that the densities and ___________of ice and liquid water are much closer to each other than to steam Notice that the densities of ice is ______ than the density of liquid water. This is not the norm, but is vital to the development of life as we know it. Tro: Chemistry: A Molecular Approach, 2/e

Degrees of Freedom Particles may have one or several types of ________________ and various degrees of each type __________ freedom is the ability to move from one position in space to another _________freedom is the ability to reorient the particles direction in space __________freedom is the ability to oscillate about a particular point in space Tro: Chemistry: A Molecular Approach, 2/e

Solids The particles in a solid are _______close together and are ______ in position though they may vibrate The close packing of the particles results in solids being ____________ The inability of the particles to move around results in solids retaining their ____________when placed in a new container, and prevents the solid from flowing Tro: Chemistry: A Molecular Approach, 2/e

Solids Some solids have their particles arranged in an orderly geometric pattern – we call these __________________ salt and diamonds Other solids have particles that do not show a regular geometric pattern over a long range – we call these ________________ plastic and glass Tro: Chemistry: A Molecular Approach, 2/e

Liquids The particles in a liquid are closely packed, but they have _________________________ The close packing results in liquids being ______________ But the ability of the particles to move allows liquids to take the shape of their container and to flow – however, ____________________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Gases There is a large amount of space between the particles
In the gas state, the particles have ____________of motion and are not held together The particles are constantly flying around, bumping into each other and the container There is a large amount of space between the particles compared to the size of the particles therefore the ____________of the gas state of a material is much larger than the ____________of the solid or liquid states Tro: Chemistry: A Molecular Approach, 2/e

Gases Because there is a lot of empty space, the particles can be squeezed closer together – therefore gases are _________________ Because the particles are not held in close contact and are moving freely, gases expand to fill and take the shape of their container, _______________ Tro: Chemistry: A Molecular Approach, 2/e

Compressibility Tro: Chemistry: A Molecular Approach, 2/e

Kinetic – Molecular Theory
What state a material is in depends largely on two major factors 1. ____________________________________ 2. _____________________________________ These two factors are in competition with each other Tro: Chemistry: A Molecular Approach, 2/e

States and Degrees of Freedom
The molecules in ________have complete freedom of motion __________________________________________ The molecules in a ________ are locked in place, they cannot move around ________________________________________________________________________________________ The molecules in a _________ have limited freedom – they can move around a little within the structure of the liquid ____________________________________________________________________________________________________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Kinetic Energy Increasing kinetic energy increases the _____________ energy of the particles The more motion energy the molecules have, the more freedom they can have The average kinetic energy is directly proportional to the temperature _________________________ Tro: Chemistry: A Molecular Approach, 2/e

Attractive Forces The particles are attracted to each other by electrostatic forces The strength of the attractive forces varies, some are small and some are large The strength of the attractive forces depends on the kind(s) of particles The stronger the attractive forces between the particles, the more they resist moving though no material completely lacks particle motion Tro: Chemistry: A Molecular Approach, 2/e

Kinetic–Molecular Theory of Gases
When the kinetic energy is so large it overcomes the attractions between particles, the material will be a ___________________ In an ideal gas, the particles have complete freedom of motion – especially _____________ This allows gas particles to expand to fill their container _____________________ It also leads to there being large spaces between the particles ___________________________ Tro: Chemistry: A Molecular Approach, 2/e

Gas Structure Gas molecules are rapidly moving in random straight lines, and are free from sticking to each other. Tro: Chemistry: A Molecular Approach, 2/e

Kinetic–Molecular Theory of Solids
When the attractive forces are strong enough so the kinetic energy cannot overcome it at all, the material will be a _____________ In a solid, the particles are packed together without any _________________ ___________________ motion the only freedom they have is ________________ motion Tro: Chemistry: A Molecular Approach, 2/e

Kinetic–Molecular Theory of Liquids
When the attractive forces are strong enough so the kinetic energy can only partially overcome them, the material will be a _______ In a liquid, the particles are packed together with only very limited _______________ freedom Tro: Chemistry: A Molecular Approach, 2/e

Explaining the Properties of Liquids
Liquids have higher __________ than gases and are incompressible because the particles are in contact They have an ___________ shape because the limited translational freedom of the particles allows them to move around enough to get to the container walls It also allows them _____________ But they have a definite volume because the limit on their freedom keeps the particles from escaping each other Tro: Chemistry: A Molecular Approach, 2/e

Phase Changes Because the attractive forces between the molecules are fixed, changing the material’s _______ requires changing the amount of kinetic energy the particles have, or limiting their freedom Solids ____ when heated because the particles gain enough kinetic energy to partially overcome the _________ forces Liquids _____ when heated because the particles gain enough kinetic energy to completely overcome the attractive forces ____________________________________________________________________________________________________________ Gases can be _____________ by decreasing the temperature and/or increasing the pressure pressure can be __________by decreasing the gas volume reducing the volume reduces the amount of ____________ freedom the particles have Tro: Chemistry: A Molecular Approach, 2/e

Phase Changes Tro: Chemistry: A Molecular Approach, 2/e

Lesson 2 Intermolecular Forces: The Forces that Hold Condensed States Together Tro: Chemistry: A Molecular Approach

Intermolecular Attractions
The ___________________between the particles of a substance determines its state At room temperature, moderate to strong attractive forces result in materials being _________________________________ The stronger the attractive forces are, the higher will be the ____________of the liquid and the _______________of the solid other factors also influence the melting point Tro: Chemistry: A Molecular Approach, 2/e

Why Are Molecules Attracted to Each Other?
Intermolecular attractions are due to ______________between opposite charges + ion to − ion + end of polar molecule to − end of polar molecule (dipole-dipole) H-bonding especially strong even nonpolar molecules will have temporary charges Larger charge = __________ attraction Longer distance = ________ attraction However, these attractive forces are small relative to the bonding forces between atoms generally smaller charges generally over much larger distances Tro: Chemistry: A Molecular Approach, 2/e

Trends in the Strength of Intermolecular Attraction
The _________________ the attractions between the atoms or molecules, the ______ energy it will take to separate them Boiling a liquid requires we add enough energy to overcome all the attractions between the particles However, not breaking the covalent bonds ________________________________________________________________________________________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Kinds of Attractive Forces
Temporary polarity in the molecules due to unequal electron distribution leads to attractions called __________________ Permanent polarity in the molecules due to their structure leads to attractive forces called __________________________ An especially strong dipole–dipole attraction results when H is attached to an extremely electronegative atom. These are called _______________________. Tro: Chemistry: A Molecular Approach, 2/e

Dispersion Forces _____________ in the electron distribution in atoms and molecules result in a temporary dipole region with ____________ electron density has partial (─) charge region with ___________ electron density has partial (+) charge The attractive forces caused by these temporary dipoles are called _______________ aka _________________(which is what I call them!) _____ molecules and atoms will have them As a temporary dipole is established in one molecule, it __________ a dipole in all the surrounding molecules Tro: Chemistry: A Molecular Approach, 2/e

Dispersion Force ______________________________________________
Comment on this picture here! _______________________ ______________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Size of the Induced Dipole
larger molecules have more electrons, leading to increased polarizability Size of the Induced Dipole The magnitude of the induced dipole depends on several factors _______________ of the electrons volume of the electron cloud ________________________________________________________________ Shape of the molecule ________________________________________________________________________________________________ + - molecules that are flat have more surface interaction than spherical ones + - + − Tro: Chemistry: A Molecular Approach, 2/e

Effect of Molecular Size on Size of Dispersion Force
The Noble gases are all nonpolar atomic elements As the molar mass _______, the number of electrons ________. Therefore the strength of the dispersion forces ______________. The stronger the attractive forces between the molecules, the __________________ will be. Tro: Chemistry: A Molecular Approach, 2/e

What is this graph showing?
Tro: Chemistry: A Molecular Approach, 2/e

Properties of Straight Chain Alkanes NonPolar Molecules

Boiling Points of n-Alkanes
What is this data showing? Tro: Chemistry: A Molecular Approach, 2/e

What is this graph showing?

Effect of Molecular Shape on Size of Dispersion Force
the __________ surface-to-surface contact between molecules in n-pentane results in ________ dispersion force attractions Tro: Chemistry: A Molecular Approach, 2/e

Alkane Boiling Points Branched chains have ______ BPs than straight chains The straight chain isomers have more _____________________________ contact Tro: Chemistry: A Molecular Approach, 2/e

Practice – Choose the Substance in Each Pair with the Higher Boiling Point
a) CH C4H10 b) C6H12 C6H12 Tro: Chemistry: A Molecular Approach, 2/e

Dipole–Dipole Attractions
Polar molecules have a ___________________ because of bond polarity and shape dipole moment as well as the always present induced dipole The permanent dipole adds to the attractive forces between the molecules ______________________________________________________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Effect of Dipole–Dipole Attraction on Boiling and Melting Points
What is this data showing? Tro: Chemistry: A Molecular Approach, 2/e

What is this Data showing? Tro: Chemistry: A Molecular Approach, 2/e

Example 11.1b: Determine if dipole–dipole attractions occur between CH2Cl2 molecules
Given: Find: CH2Cl2, EN C = 2.5, H = 2.1, Cl = 3.0 If there are dipole–dipole attractions Conceptual Plan: Relationships: Lewis Structure Bond Polarity Molecule Formula EN Difference Shape molecules that have dipole–dipole attractions must be polar Solution: Tro: Chemistry: A Molecular Approach, 2/e

Practice – Choose the substance in each pair with the higher boiling point
a) CH2FCH2F CH3CHF2 b) or Tro: Chemistry: A Molecular Approach, 2/e

Hydrogen Bonding When ___________________atom is bonded to hydrogen, it strongly pulls the bonding electrons toward it __________________________ Because hydrogen has no other electrons, when its electron is pulled away, the nucleus becomes __________________ ________________________ The exposed proton acts as a very strong center of positive charge, attracting all the electron clouds from neighboring molecules Tro: Chemistry: A Molecular Approach, 2/e

H-Bonding HF Tro: Chemistry: A Molecular Approach, 2/e

H-Bonding in Water Tro: Chemistry: A Molecular Approach, 2/e

H-Bonds Hydrogen bonds are _______________________intermolecular attractive forces stronger than ______________________________ Substances that can hydrogen bond will have _________________________________than similar substances that cannot But hydrogen bonds are not nearly as strong as __________________________ 2 to 5% the strength of covalent bonds Tro: Chemistry: A Molecular Approach, 2/e

Effect of H-Bonding on Boiling Point
What is this data showing you? Tro: Chemistry: A Molecular Approach, 2/e

HF, H2O, and NH3 have unusually strong dipole-dipole attractions, called hydrogen bonds. Therefore they have higher boiling points than you would expect from the general trends. Polar molecules, such as the hydrides of Groups 5–7, have both dispersion forces and dipole–dipole attractions. Therefore they have higher boiling points than the corresponding Group 4 molecules. For nonpolar molecules, such as the hydrides of Group 4, the intermolecular attractions are due to dispersion forces. Therefore they increase down the column, causing the boiling point to increase. Tro: Chemistry: A Molecular Approach, 2/e

Example 11.2: One of these compounds is a liquid at room temperature (the others are gases). Which one and why? MM = 30.03 Polar No H-Bonds MM = 34.03 Polar No H-Bonds MM = 34.02 Polar H-Bonds Tro: Chemistry: A Molecular Approach, 2/e

a) CH3OH CH3CHF2 b) CH3-O-CH2CH3 CH3CH2CH2NH2
Practice – Choose the substance in each pair that is a liquid at room temperature (the other is a gas) a) CH3OH CH3CHF2 b) CH3-O-CH2CH3 CH3CH2CH2NH2 Tro: Chemistry: A Molecular Approach, 2/e

Attractive Forces and Solubility
Solubility depends, in part, on the attractive forces of the solute and solvent molecules ________________________ ________________________________________ Polar substances dissolve in polar solvents ____________________________________________ Nonpolar molecules dissolve in nonpolar solvents ________________________________ Many molecules have both hydrophilic and hydrophobic parts – solubility in water becomes a _______________between the attraction of the polar groups for the water and the attraction of the nonpolar groups for their own kind Tro: Chemistry: A Molecular Approach, 2/e

Immiscible Liquids Pentane, C5H12 is a __________ molecule.
Water is a ________molecule. The attractive forces between the water molecules is much stronger than their attractions for the pentane molecules. The result is the liquids are ______________. Tro: Chemistry: A Molecular Approach, 2/e

Polar Solvents Water Ethanol (ethyl alcohol) Dichloromethane
(methylene chloride) Tro: Chemistry: A Molecular Approach, 2/e

Nonpolar Solvents Tro: Chemistry: A Molecular Approach, 2/e

Ion–Dipole Attraction
In a mixture, __________ from an ionic compound are attracted to the _________ of polar molecules The strength of the ___________ attraction is one of the main factors that determines the solubility of ionic compounds in water Tro: Chemistry: A Molecular Approach, 2/e

Practice – Choose the substance in each pair that is more soluble in water
a) CH3OH CH3CHF2 b) CH3CH2CH2CH2CH3 CH3Cl Tro: Chemistry: A Molecular Approach, 2/e

Summary Dispersion forces are the _____________ of the intermolecular attractions Dispersion forces are present in _______________________________ The magnitude of the dispersion forces increases with _______________ Polar molecules also have ______________________attractive forces Tro: Chemistry: A Molecular Approach, 2/e

Summary (cont’d) ____________________are the strongest of the intermolecular attractive forces a pure substance can have Hydrogen bonds will be present when a molecule has H directly bonded to either __________________atoms only example of H bonded to F is ___________ ______________ attractions are present in mixtures of ionic compounds with polar molecules. ______________ attractions are the strongest intermolecular attraction ________________ attractions are especially important in aqueous solutions of ionic compounds Tro: Chemistry: A Molecular Approach, 2/e

Tro: Chemistry: A Molecular Approach, 2/e

Properties & Structure
Lesson 3: Liquids Properties & Structure Tro: Chemistry: A Molecular Approach, 2/e

Surface Tension Surface tension is a property of liquids that results from the tendency of liquids ___________________________ To minimize their surface area, liquids form drops that are ______________ as long as there is no gravity Tro: Chemistry: A Molecular Approach, 2/e

Surface Tension The layer of molecules on the surface behave differently than the interior ________________________________________________________________________________ The surface layer acts like an elastic skin allowing you to “float” a paper clip even though steel is denser than water Tro: Chemistry: A Molecular Approach, 2/e

Surface Tension Because they have fewer neighbors to attract them, the surface molecules are __________than those in the interior have a higher potential energy The surface tension of a liquid is the energy required to increase the surface area a given amount surface tension of H2O = 72.8 mJ/m2 at room temperature surface tension of C6H6 = 28 mJ/m2 Tro: Chemistry: A Molecular Approach, 2/e

Factors Affecting Surface Tension
The stronger the __________________forces, the higher the surface tension will be _____________________of a liquid reduces its surface tension raising the temperature of the liquid increases the average kinetic energy of the molecules the increased molecular motion makes it easier to stretch the surface Tro: Chemistry: A Molecular Approach, 2/e

What does this graph show?

Viscosity ____________ is the resistance of a liquid to flow
1 poise = 1 P = 1 g/cm∙s often given in centipoise, cP H2O = 1 cP at room temperature Larger intermolecular attractions = ____ viscosity Tro: Chemistry: A Molecular Approach, 2/e

Factors Affecting Viscosity
The ___________ the intermolecular attractive forces, the ___________ the liquid’s viscosity will be The more ___________ the molecular shape, the lower the viscosity will be molecules roll more easily less surface-to-surface contact lowers attractions ____________________of a liquid reduces its viscosity raising the temperature of the liquid increases the average kinetic energy of the molecules the increased molecular motion makes it easier to overcome the intermolecular attractions and flow Tro: Chemistry: A Molecular Approach, 2/e

What does this graph show?
Insert Table 11.6 Tro: Chemistry: A Molecular Approach, 2/e

Capillary Action _________________is the ability of a liquid to flow up a thin tube against the influence of gravity the narrower the tube, the higher the liquid rises Capillary action is the result of two forces working in conjunction, the _____________________________________ _________ forces hold the liquid molecules together _______ forces attract the outer liquid molecules to the tube’s surface Tro: Chemistry: A Molecular Approach, 2/e

Capillary Action The __________ forces pull the surface liquid up the side of the tube, and the cohesive forces pull the interior liquid with it The liquid _____ up the tube until the force of gravity counteracts the capillary action forces The ______ the tube diameter, the higher the liquid will rise up the tube Tro: Chemistry: A Molecular Approach, 2/e

Meniscus The curving of the liquid surface in a thin tube is due to the competition between __________________forces The ______ of water is concave in a glass tube because its adhesion to the glass is stronger than its cohesion for itself The meniscus of mercury is _____ in a glass tube because its cohesion for itself is stronger than its adhesion for the glass metallic bonds are stronger than intermolecular attractions Tro: Chemistry: A Molecular Approach, 2/e

Lesson 4 Vaporization and Vapor Pressure
Tro: Chemistry: A Molecular Approach

The Molecular Dance Molecules in the liquid are constantly _________________ vibrational, and limited rotational and translational The __________________is proportional to the temperature However, some molecules have more kinetic energy than the average, and others have less Tro: Chemistry: A Molecular Approach, 2/e

Vaporization If these high energy molecules are at the surface, they may have enough energy to overcome the attractive forces therefore – ________________________________________________________ This will allow them to escape the liquid and become a _________ Tro: Chemistry: A Molecular Approach, 2/e

Distribution of Thermal Energy
Only a small fraction of the molecules in a liquid have enough energy to escape But, as the temperature increases, the fraction of the molecules with “escape energy” increases _____________________________________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Condensation Some molecules of the vapor will lose energy through molecular collisions The result will be that some of the molecules will get captured back into the liquid when they collide with it Also some may stick and gather together to form droplets of liquid particularly on surrounding surfaces We call this process _____________________ Tro: Chemistry: A Molecular Approach, 2/e

Evaporation vs. Condensation
___________________________are opposite processes In an open container, the vapor molecules generally spread out faster than they can condense The net result is that the rate of vaporization is ________ than the rate of condensation, and there is a net loss of liquid However, in a closed container, the vapor is not allowed to spread out indefinitely The net result in a closed container is that at some time the rates of vaporization and condensation __________ Tro: Chemistry: A Molecular Approach, 2/e

Effect of Intermolecular Attraction on Evaporation and Condensation
The weaker the attractive forces between molecules, the less energy they will need to vaporize Also, weaker attractive forces means that more energy will need to be removed from the vapor molecules before they can condense The net result will be more molecules in the vapor phase, and a liquid that evaporates faster – _________________________________________ Liquids that evaporate easily are said to be _______ e.g., gasoline, fingernail polish remover liquids that do not evaporate easily are called __________ e.g., motor oil Tro: Chemistry: A Molecular Approach, 2/e

Energetics of Vaporization
When the high energy molecules are lost from the liquid, it lowers the average kinetic energy If energy is not drawn back into the liquid, its temperature will decrease – therefore, ____________________________________ and condensation is an exothermic process Vaporization requires input of energy to overcome the attractions between molecules Tro: Chemistry: A Molecular Approach, 2/e

Heat of Vaporization The amount of heat energy required to vaporize one mole of the liquid is called the ______________________, DHvap sometimes called the enthalpy of vaporization Always endothermic, therefore DHvap is + Somewhat temperature dependent DHcondensation = −DHvaporization Tro: Chemistry: A Molecular Approach, 2/e

Example 11.3: Calculate the mass of water that can be vaporized with 155 kJ of heat at 100 °C
Given: Find: 155 kJ g H2O Conceptual Plan: Relationships: 1 mol H2O = 40.7 kJ, 1 mol = g kJ mol H2O g H2O Solution: Check: because the given amount of heat is almost 4x the DHvap, the amount of water makes sense Tro: Chemistry: A Molecular Approach, 2/e

Practice – Calculate the amount of heat needed to vaporize 90
Practice – Calculate the amount of heat needed to vaporize 90.0 g of C3H7OH at its boiling point (DHvap = 39.9 kJ/mol) Tro: Chemistry: A Molecular Approach, 2/e

Dynamic Equilibrium In a closed container, once the rates of vaporization and condensation are equal, the total amount of vapor and liquid will not change Evaporation and condensation are still occurring, but because they are opposite processes, there is no net gain or loss of either vapor or liquid When two opposite processes reach the same rate so that there is no gain or loss of material, we call it a ______________________________ this does not mean there are equal amounts of vapor and liquid – it means that they are ___________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Dynamic Equilibrium Tro: Chemistry: A Molecular Approach, 2/e

Vapor Pressure The pressure exerted by the vapor when it is in dynamic equilibrium with its liquid is called the ___________________________ remember using Dalton’s Law of Partial Pressures to account for the pressure of the water vapor when collecting gases by water displacement? The weaker the attractive forces between the molecules, the more molecules will be in the vapor Therefore, _______________________________________ the higher the vapor pressure, the more volatile the liquid Tro: Chemistry: A Molecular Approach, 2/e

Vapor–Liquid Dynamic Equilibrium
If the __________ of the chamber is increased, it will decrease the pressure of the vapor inside the chamber at that point, there are fewer vapor molecules in a given volume, causing the rate of condensation to slow Therefore, for a period of time, the rate of vaporization will be faster than the rate of condensation, and the amount of vapor will increase Eventually enough vapor accumulates so that the rate of the condensation increases to the point where it is once again as fast as evaporation __________________________ At this point, the vapor pressure will be the same as it was before Tro: Chemistry: A Molecular Approach, 2/e

Changing the Container’s Volume Disturbs the Equilibrium
Initially, the rate of vaporization and condensation are equal and the system is in dynamic equilibrium When the volume is increased, the rate of vaporization becomes faster than the rate of condensation When the volume is decreased, the rate of vaporization becomes slower than the rate of condensation Tro: Chemistry: A Molecular Approach, 2/e

Dynamic Equilibrium A system in dynamic equilibrium can respond to changes in the conditions _______________________________________________________________________________________________________________ Tro: Chemistry: A Molecular Approach, 2/e

Vapor Pressure vs. Temperature
Increasing the temperature increases the number of molecules able to escape the liquid The net result is that __________________________________________________________________________ Small changes in temperature can make big changes in vapor pressure the rate of growth depends on strength of the intermolecular forces Tro: Chemistry: A Molecular Approach, 2/e

Vapor Pressure Curves normal BP 100 °C BP Ethanol at 500 mmHg 68.1°C

Practice – Which of the following is the most volatile?
a) water b) TiCl4 c) ether d) ethanol e) acetone a) water b) TiCl4 c) ether d) ethanol e) acetone Tro: Chemistry: A Molecular Approach, 2/e

Practice – Which of the following has the strongest Intermolecular attractions?

Boiling Point When the temperature of a liquid reaches a point where its vapor pressure is the same as the external pressure, vapor bubbles can form anywhere in the liquid not just on the surface This phenomenon is what is called _________and the temperature at which the vapor pressure = external pressure is the ____________________ Tro: Chemistry: A Molecular Approach, 2/e

Boiling Point ______________________________________________________________________________ The lower the external pressure, the lower the boiling point of the liquid Tro: Chemistry: A Molecular Approach, 2/e

Practice – Which of the following has the highest normal boiling point?

The Critical Point The temperature required to produce a supercritical fluid is called the _______________________________ The pressure at the critical temperature is called the ________________________ At the critical temperature or higher temperatures, the gas cannot be condensed to a liquid, no matter how high the pressure gets Tro: Chemistry: A Molecular Approach, 2/e

Lesson 5 Sublimation and Fusion Tro: Chemistry: A Molecular Approach

Sublimation and Deposition
Molecules in the solid have thermal energy that allows them to vibrate Surface molecules with sufficient energy may break free from the surface and become a gas – this process is called ____________________ The capturing of vapor molecules into a solid is called _______________________ The solid and vapor phases exist in dynamic equilibrium in a closed container at temperatures below the melting point therefore, molecular solids have a vapor pressure sublimation solid gas deposition Tro: Chemistry: A Molecular Approach, 2/e

Sublimation Tro: Chemistry: A Molecular Approach, 2/e

Melting = Fusion As a solid is heated, its temperature rises and the molecules vibrate more _________________ Once the temperature reaches the melting point, the molecules have sufficient energy to overcome some of the attractions that hold them in position and the solid melts (or fuses) The opposite of _____________________ Tro: Chemistry: A Molecular Approach, 2/e

Heating Curve of a Solid
As you heat a solid, its temperature increases linearly until it reaches the melting point q = mass x Cs x DT Once the temperature reaches the melting point, all the added heat goes into melting the solid – ________________________ Once all the solid has been turned into liquid, the temperature can again start to rise ice/water will always have a temperature of 0 °C at 1 atm Tro: Chemistry: A Molecular Approach, 2/e

Energetics of Melting When the high energy molecules are lost from the solid, it lowers the average kinetic energy If energy is not drawn back into the solid its temperature will decrease – therefore, _________________________________ and freezing is an exothermic process Melting requires input of energy to overcome the attractions between molecules Tro: Chemistry: A Molecular Approach, 2/e

Heat of Fusion The amount of heat energy required to melt one mole of the solid is called the ________________, DHfus sometimes called the enthalpy of fusion Always endothermic, therefore DHfus is + Somewhat temperature dependent DHcrystallization = −DHfusion Generally much less than DHvap DHsublimation = DHfusion + DHvaporization Tro: Chemistry: A Molecular Approach, 2/e

Heats of Fusion and Vaporization
What is this data Showing? Tro: Chemistry: A Molecular Approach, 2/e

Heating Curve of Water Tro: Chemistry: A Molecular Approach, 2/e

Segment 1 Heating 1.00 mole of ice at −25.0 °C up to the melting point, 0.0 °C q = mass x Cs x DT mass of 1.00 mole of ice = 18.0 g Cs = 2.09 J/mol∙°C Tro: Chemistry: A Molecular Approach, 2/e

Segment 2 Melting 1.00 mole of ice at the melting point, 0.0 °C
q = n∙DHfus n = 1.00 mole of ice DHfus = 6.02 kJ/mol Tro: Chemistry: A Molecular Approach, 2/e

Segment 3 Heating 1.00 mole of water at 0.0 °C up to the boiling point, °C q = mass x Cs x DT mass of 1.00 mole of water = 18.0 g Cs = 2.09 J/mol∙°C Tro: Chemistry: A Molecular Approach, 2/e

Segment 4 Boiling 1.00 mole of water at the boiling point, 100.0 °C
q = n∙DHvap n = 1.00 mole of ice DHfus = 40.7 kJ/mol Tro: Chemistry: A Molecular Approach, 2/e

Segment 5 Heating 1.00 mole of steam at 100.0 °C up to 125.0 °C
q = mass x Cs x DT mass of 1.00 mole of water = 18.0 g Cs = 2.01 J/mol∙°C Tro: Chemistry: A Molecular Approach, 2/e

Practice – How much heat, in kJ, is needed to raise the temperature of a 12.0 g benzene sample from −10.0 °C to 25.0 °C? Tro: Chemistry: A Molecular Approach, 2/e

Practice – How much heat is needed to raise the temperature of a 12
Practice – How much heat is needed to raise the temperature of a 12.0 g benzene sample from −10.0 °C to 25.0 °C? Tro: Chemistry: A Molecular Approach

Lesson 6: Phase Diagrams
Phase diagrams describe ______________________________________________________________________________ Regions represent states Lines represent ______________________ liquid/gas line is vapor pressure curve both states exist simultaneously critical point is the furthest point on the vapor pressure curve _______________is the temperature/pressure condition where all three states exist simultaneously For most substances, freezing point increases as pressure increases Tro: Chemistry: A Molecular Approach, 2/e

Phase Diagrams Pressure Liquid Solid Gas Temperature Fusion Curve
critical point melting freezing Liquid Solid Pressure normal melting pt. normal boiling pt. 1 atm Sublimation Curve triple point Vapor Pressure Curve vaporization condensation sublimation deposition Gas Temperature Tro: Chemistry: A Molecular Approach, 2/e

Phase Diagram of Water Pressure Water Ice Steam Temperature critical
point 374.1 °C 217.7 atm triple Ice Water Steam 1 atm normal boiling pt. 100 °C melting pt. 0 °C 0.01 °C 0.006 atm Tro: Chemistry: A Molecular Approach, 2/e

Phase Diagram of CO2 Liquid Pressure Solid Gas Temperature critical
point 31.0 °C 72.9 atm triple Solid Liquid Gas 1 atm -56.7 °C 5.1 atm normal sublimation pt. -78.5 °C Tro: Chemistry: A Molecular Approach, 2/e

Practice – Consider the phase diagram of CO2 shown
Practice – Consider the phase diagram of CO2 shown. What phase(s) is/are present at each of the following conditions? 20.0 °C, 72.9 atm liquid −56.7 °C, 5.1 atm solid, liquid, gas 10.0 °C, 1.0 atm gas −78.5 °C, 1.0 atm solid, gas 50.0 °C, 80.0 atm scf 20.0 °C, 72.9 atm −56.7 °C, 5.1 atm 10.0 °C, 1.0 atm −78.5 °C, 1.0 atm 50.0 °C, 80.0 atm Tro: Chemistry: A Molecular Approach, 2/e

Water – An Extraordinary Substance
Water is a liquid at room temperature most molecular substances with similar molar masses are gases at room temperature e.g. NH3, CH4 due to H-bonding between molecules Water is an excellent solvent – dissolving many ionic and polar molecular substances because of its large dipole moment even many small nonpolar molecules have some solubility in water e.g. O2, CO2 Water has a very high specific heat for a molecular substance moderating effect on coastal climates Water expands when it freezes at a pressure of 1 atm about 9% making ice less dense than liquid water Tro: Chemistry: A Molecular Approach, 2/e

Properties & Structure
Solids Properties & Structure Tro: Chemistry: A Molecular Approach, 2/e

Crystal Lattice When allowed to cool slowly, the particles in a liquid will arrange themselves to give the maximum attractive forces therefore minimize the energy The result will generally be a crystalline solid The arrangement of the particles in a crystalline solid is called the crystal lattice The smallest unit that shows the pattern of arrangement for all the particles is called the unit cell Tro: Chemistry: A Molecular Approach, 2/e

Chapter 11 Liquids, Solids, and Intermolecular Forces

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Chapter 11 Liquids, Solids, and Intermolecular Forces

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