The States Of MatterThe States Of Matter

All matter is made of something, All matter is made of something, even if it looks like nothing.even if it looks like nothing.

We make classifications according We make classifications according to its properties, both chemical to its properties, both chemical

and physicaland physical

Three States of MatterThree States of Matter Solid: strong interactions Solid: strong interactions

Fixed shapeFixed shape Not compressibleNot compressible RigidRigid DenseDense

Liquid: medium interactionsLiquid: medium interactions

LiquidLiquid Not rigidNot rigid Assumes shape of containerAssumes shape of container Not compressibleNot compressible DenseDense

Gas: no interactionsGas: no interactions

Not rigidNot rigid Completely fills containerCompletely fills container CompressibleCompressible Low densityLow density

Plasma: the fourth statePlasma: the fourth state

At very high energies (temperatures) all the At very high energies (temperatures) all the electrons are removed from the atomselectrons are removed from the atoms

Not an important state for chemistryNot an important state for chemistry

Atom motion and temperatureAtom motion and temperature

Atoms in molecules have three types of Atoms in molecules have three types of motionmotion Rotation – moving about the centre of massRotation – moving about the centre of mass Vibration – vibrating about the centre of massVibration – vibrating about the centre of mass Translation – movement of the centre of massTranslation – movement of the centre of mass

As temperature increases, the energies of As temperature increases, the energies of all types of motion increaseall types of motion increase

SolidsSolids

Atoms in solids rotate and vibrate but do not Atoms in solids rotate and vibrate but do not translate translate

Melting occurs when the translational energy of Melting occurs when the translational energy of the atoms is sufficient to break free of the latticethe atoms is sufficient to break free of the lattice

Usually this is a very well defined pointUsually this is a very well defined point With amorphous solids it can be smeared out – With amorphous solids it can be smeared out –

softening of fatssoftening of fats

Vapour pressure and boilingVapour pressure and boiling

Molecules do not all have the same energyMolecules do not all have the same energy High energy molecules escape the liquid – vapour High energy molecules escape the liquid – vapour

pressurepressure When vapour pressure = atmospheric pressure When vapour pressure = atmospheric pressure

boiling occursboiling occurs Sublimation is direct transition of solid to gas (dry Sublimation is direct transition of solid to gas (dry

ice)ice)

Kinetic molecular theory and Kinetic molecular theory and pressure – a case for atomspressure – a case for atoms

Pumping up a tire increases the number of Pumping up a tire increases the number of moleculesmolecules

Pressure is caused by the energetic molecules Pressure is caused by the energetic molecules striking the tire wallstriking the tire wall

More molecules – higher pressureMore molecules – higher pressure Higher temperature – higher pressureHigher temperature – higher pressure

Under pressureUnder pressure

Gases exert pressure by virtue of motionGases exert pressure by virtue of motion Gravity makes the air density higher near Gravity makes the air density higher near

the earth’s surfacethe earth’s surface Pressure decreases with elevationPressure decreases with elevation

Atmospheric pressureAtmospheric pressure

The weight of the air supports a column of The weight of the air supports a column of mercury 760 mm highmercury 760 mm high

BarometerBarometer is used for measuring is used for measuring atmospheric pressureatmospheric pressure

Atmospheric pressure changes with the Atmospheric pressure changes with the weatherweather

The atmosphere is layeredThe atmosphere is layered

TroposphereTroposphere Where the weather happensWhere the weather happens

StratosphereStratosphere Where the ozone isWhere the ozone is MesosphereMesosphere IonosphereIonosphere

The brutal strength of solar radiation ionizes all the The brutal strength of solar radiation ionizes all the components – permits transmission of radio signals components – permits transmission of radio signals around the earth without need of mirrorsaround the earth without need of mirrors

Units of pressureUnits of pressure

mm (or cm) of mercury mm (or cm) of mercury Atmospheric pressure = 760 mm HgAtmospheric pressure = 760 mm Hg

Pascal is SI unit for pressurePascal is SI unit for pressure Atmospheric pressure = 101 000 kPaAtmospheric pressure = 101 000 kPa

Pounds/square inchPounds/square inch Atmospheric pressure = 14.7 lb/inAtmospheric pressure = 14.7 lb/in22

Standard temperature and pressure Standard temperature and pressure (STP)(STP)

Standard conditions allow direct comparison Standard conditions allow direct comparison of properties of different substancesof properties of different substances Standard temperature is 273 K (0Standard temperature is 273 K (0ºC)ºC) Standard pressure is 760 mm HgStandard pressure is 760 mm Hg

At STP, 1 mole of At STP, 1 mole of anyany ideal gas occupies ideal gas occupies 22.414 L22.414 L

Gas laws: experience in math formGas laws: experience in math form

The properties of gases can be described by a The properties of gases can be described by a number of simple lawsnumber of simple laws

The laws establish quantitative relationships The laws establish quantitative relationships between different variablesbetween different variables

They are largely intuitively obvious and familiarThey are largely intuitively obvious and familiar

The four variablesThe four variables

Pressure (P)Pressure (P) Volume (V)Volume (V) Temperature (T in Kelvin)Temperature (T in Kelvin) Number of molecules (n in moles)Number of molecules (n in moles)

Variables and constantsVariables and constants

In the elementary gas laws two of the four In the elementary gas laws two of the four variables are kept constantvariables are kept constant

Each law describes how one variable reacts Each law describes how one variable reacts to changes in another variableto changes in another variable

All the simple laws can be integrated into All the simple laws can be integrated into one combined gas lawone combined gas law

Boyle’s lawBoyle’s law

The first experimental gas The first experimental gas lawlaw

Pressure increases, volume Pressure increases, volume decreases (T, n constant)decreases (T, n constant)

1PV

Charles’ LawCharles’ Law

As temperature increases, As temperature increases, volume increases (P, n volume increases (P, n constant)constant) Temperature must be Temperature must be

measured in Kelvinmeasured in Kelvin

V T

Absolute zeroAbsolute zero

Gay-Lussac observed V changed by 1/273 Gay-Lussac observed V changed by 1/273 of value at 0of value at 0ºCºC

Plotted as V = Plotted as V = kkT (T = ºC + 273), V = 0 at T T (T = ºC + 273), V = 0 at T = 0= 0

Does the gas actually occupy zero volume?Does the gas actually occupy zero volume? No, at lower T the law is not followedNo, at lower T the law is not followed

Combined gas lawCombined gas law

Fold together Boyle and Charles:Fold together Boyle and Charles: PP11VV11/T/T11 = P = P22VV22/T/T22

Given five of the variables, find the sixthGiven five of the variables, find the sixth Units must be consistentUnits must be consistent Temperature in KelvinTemperature in Kelvin

Gay-Lussac and law of combining Gay-Lussac and law of combining volumesvolumes

When gases react at constant temperature When gases react at constant temperature and pressure, they combine in volumes that and pressure, they combine in volumes that are related to each other as ratios of small are related to each other as ratios of small whole numberswhole numbers

His experiments with hydrogen and oxygen His experiments with hydrogen and oxygen had implications for the understanding of the had implications for the understanding of the atom and the structures of simple moleculesatom and the structures of simple molecules

Avogadro’s LawAvogadro’s Law

As the number of moles of As the number of moles of gas increases, so does the gas increases, so does the volume (P, T constant)volume (P, T constant)

V n

Dalton’s law of partial pressuresDalton’s law of partial pressures

A mixture of gases exerts a pressure as if all A mixture of gases exerts a pressure as if all the gases were independent of one anotherthe gases were independent of one another

Total pressure is the sum of the pressures Total pressure is the sum of the pressures exerted by each oneexerted by each one

P = pP = p11 + p + p22 + p + p33 + … + …

Real world applications 1:Real world applications 1:Henry’s Law and sodie popHenry’s Law and sodie pop

The quantity of gas dissolved in a liquid The quantity of gas dissolved in a liquid depend directly on the pressure of that gas depend directly on the pressure of that gas above the liquidabove the liquid

Under pressure the COUnder pressure the CO22 in the liquid is kept in the liquid is kept in solutionin solution

Open the cap and the COOpen the cap and the CO22 rapidly escapes rapidly escapes

Real world applications 2:Real world applications 2:The science of breathingThe science of breathing

The gas laws explain the mechanics of The gas laws explain the mechanics of breathing: the transport of oxygen from the breathing: the transport of oxygen from the lungs and exchange with carbon dioxide lungs and exchange with carbon dioxide produced in the body.produced in the body.