energy and the states of matter forces between particles states of matter changes in state
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Energy and the States Energy and the States Of MatterOf Matter
Forces between particlesForces between particles
States of matterStates of matter
Changes in stateChanges in state
Learning objectivesLearning objectives
Describe types of motion in moleculesDescribe types of motion in molecules Distinguish among states of matter based Distinguish among states of matter based
on propertieson properties Describe four types of intermolecular forcesDescribe four types of intermolecular forces Identify main forces operating in simple Identify main forces operating in simple
substancessubstances Perform calculations of heat involved in Perform calculations of heat involved in
changes of statechanges of state
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
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
May the force be with youMay the force be with you
Covalent and ionic bonds are the Covalent and ionic bonds are the intraintramolecular forces that hold the atoms in molecular forces that hold the atoms in molecules togethermolecules together
InterIntermolecular forces hold the molecules molecular forces hold the molecules togethertogether
Collectively, the intermolecular forces are Collectively, the intermolecular forces are called called van der Waalsvan der Waals forces forces
All arise from electrostatic interactionsAll arise from electrostatic interactions
Intermolecular forcesIntermolecular forces
Polar molecules experience strong intermolecular Polar molecules experience strong intermolecular interactions due to existence of positive and interactions due to existence of positive and negative ends of dipolesnegative ends of dipoles
Weaker forces exist between nonpolar molecules. Weaker forces exist between nonpolar molecules. These are due to fluctuations in the electron These are due to fluctuations in the electron distributions in the molecules which create distributions in the molecules which create momentary (weak) dipoles – London forcesmomentary (weak) dipoles – London forces
Intermolecular interactions are known collectively Intermolecular interactions are known collectively as as van der Waals van der Waals forcesforces
Name of forceName of force OriginOrigin StrengthStrength
Ion-dipoleIon-dipole Between ions and Between ions and moleculesmolecules
Quite strong (10 – Quite strong (10 – 50 kJ/mol)50 kJ/mol)
Dipole-dipoleDipole-dipole Between Between permanent dipolespermanent dipoles
Weak (3 – 4 Weak (3 – 4 kJ/mol)kJ/mol)
Hydrogen bondsHydrogen bonds Polar bonds with H Polar bonds with H and (O,N)and (O,N)
Quite strong (10 – Quite strong (10 – 40 kJ/mol)40 kJ/mol)
London London dispersion dispersion forcesforces
Fluctuating dipoles in Fluctuating dipoles in non-polar bondsnon-polar bonds
Weak (1 – 10 Weak (1 – 10 kJ/mol)kJ/mol)
The Four Forces of the ApocalypseThe Four Forces of the Apocalypse
Hydrogen bonding: something about Hydrogen bonding: something about waterwater
High boiling point High boiling point compared with similar compared with similar compoundscompounds Liquid at earth temperatureLiquid at earth temperature
Solid less dense than Solid less dense than liquidliquid Essential for life on earthEssential for life on earth
High heat capacityHigh heat capacity Modifying influence on Modifying influence on
climateclimate
Universal solventUniversal solvent
Hydrogen bondingHydrogen bonding
The ultimate expression of polarityThe ultimate expression of polarity Small positive H atom exerts strong Small positive H atom exerts strong
attraction on O atomattraction on O atom Other H-bonding molecules: HF, NHOther H-bonding molecules: HF, NH33
HH22O is the supreme example: two H atoms O is the supreme example: two H atoms
and two lone pairs per moleculeand two lone pairs per molecule
HH22O has optimum combination of O has optimum combination of
lone pairs and H atomslone pairs and H atoms
CompoundCompound Number of lone Number of lone pairspairs
Number of H Number of H atomsatoms
HFHF 33 11
HH22OO 22 22
NHNH33 11 33
H bonding generates three-H bonding generates three-dimensional networkdimensional network
Ice floats!Ice floats!
Something so familiar we might believe all Something so familiar we might believe all solids float on their liquids. Not so. Water is solids float on their liquids. Not so. Water is the exception.the exception.
Hydrogen bonding and lifeHydrogen bonding and life
hold the two strands of the DNA double helix hold the two strands of the DNA double helix together together
hold polypeptides together in such secondary hold polypeptides together in such secondary structures as the alpha helix and the beta structures as the alpha helix and the beta conformationconformation
help enzymes bind to their substratehelp enzymes bind to their substrate help antibodies bind to their antigen help antibodies bind to their antigen help transcription factors bind to each otherhelp transcription factors bind to each other help transcription factors bind to DNA help transcription factors bind to DNA
Implications for life on earth Implications for life on earth
Without H-bonds Without H-bonds molecules like DNA molecules like DNA would not existwould not exist
H-bonds hold the two H-bonds hold the two strands togetherstrands together
Comparative Comparative weakness of bonding weakness of bonding allows for DNA allows for DNA replicationreplication dna
Intermolecular forces determine Intermolecular forces determine physical propertiesphysical properties
Strong ionic bonds Strong ionic bonds mean high melting mean high melting pointpoint
Dipole-dipole Dipole-dipole interactions – much interactions – much lower melting pointslower melting points
Dispersion forces only Dispersion forces only – very low melting – very low melting pointspoints
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