CHAPTER 13CHAPTER 13

Kinetic Molecular TheoryKinetic Molecular Theory(K.M.T.)(K.M.T.)

• Kinetic Theory:Kinetic Theory: – The tiny particles in all forms of matter are The tiny particles in all forms of matter are

in in

constant motion.constant motion.– Explains the properties of solids, liquids, & Explains the properties of solids, liquids, &

gases.gases.

SOLIDSSOLIDS1.1. Solids and K.M.T.Solids and K.M.T.

More closely packed than liquids or More closely packed than liquids or gases.gases.

Intermolecular forces are VERY Intermolecular forces are VERY effective.effective.

Only vibrational movement.Only vibrational movement. Crystalline vs. Amorphous (glass) Crystalline vs. Amorphous (glass)

solids.solids.

Properties of SolidsProperties of Solids1.1. Definite shape and volumeDefinite shape and volume

2.2. Melting pointMelting point: : Crystalline SolidsCrystalline Solids: Definite melting point, KE : Definite melting point, KE

of particles overcome attractive forces of of particles overcome attractive forces of solid.solid.

Amorphous SolidsAmorphous Solids: No definite melting point, : No definite melting point, Supercooled liquids.Supercooled liquids.

3. High Density and Incompressibility3. High Density and Incompressibility

4. Low diffusion rate: very slow4. Low diffusion rate: very slow

Crystalline SolidsCrystalline Solids

1. Crystal structure = 3D arrangement 1. Crystal structure = 3D arrangement of particles of crystals.of particles of crystals.

2. Unit Cell = smallest portion of a 2. Unit Cell = smallest portion of a crystal that shows the 3D structure.crystal that shows the 3D structure.

1. no definite shape or volume1. no definite shape or volume2. Particles are small, hard spheres, with 2. Particles are small, hard spheres, with

insignificant volume (very far apart).insignificant volume (very far apart).3. Particles move rapidly in constant 3. Particles move rapidly in constant

random motionrandom motion4. All collisions are perfectly elastic 4. All collisions are perfectly elastic

(Energy is transferred & not lost)(Energy is transferred & not lost)5. There are no forces of attraction or 5. There are no forces of attraction or

repulsionrepulsion between gas particles.between gas particles.

• Gas Pressure:Gas Pressure: is the result of simultaneous is the result of simultaneous collisions of billions of gascollisions of billions of gas

particles with an object.particles with an object.

GASESGASES

• Gas Pressure:Gas Pressure:

is the result of simultaneous collisions of is the result of simultaneous collisions of billions of gas particles with an object.billions of gas particles with an object.

• Vacuum:Vacuum: when no gas particles are when no gas particles are presentpresent

• Atmospheric Pressure:Atmospheric Pressure: results from the results from the collisions of air molecules with objects. collisions of air molecules with objects. Decreases as you climb a mountain b/c air Decreases as you climb a mountain b/c air layer around earth thins out at high layer around earth thins out at high elevations.elevations.

• Barometer:Barometer: measures atmospheric measures atmospheric pressurepressure– SI unit of pressure = pascal (Pa) SI unit of pressure = pascal (Pa) – Atm pressure at sea level = STP (0Atm pressure at sea level = STP (0ooC) =C) =

101.3 kPa = 760 mm Hg= 1 atm= 760 101.3 kPa = 760 mm Hg= 1 atm= 760 torr= torr=

29.92 inHg = 14.7 psi29.92 inHg = 14.7 psi

Ex: 1.50 atm = ? kPaEx: 1.50 atm = ? kPa

1.50 atm 101.3 kPa = 1.52 x 101.50 atm 101.3 kPa = 1.52 x 1022kPakPa

1 atm1 atm

UNITS OF PRESSUREUNITS OF PRESSUREUnitsUnits SymbolSymbol DefinitionDefinition

Millimeters of Millimeters of mercurymercury

mmHgmmHg Pressure of Pressure of that supports that supports 1mm of Hg in 1mm of Hg in a barometera barometer

TorricelliTorricelli torrtorr 1 torr = 1 1 torr = 1 mmHgmmHg

AtmosphereAtmosphere atmatm Average Average atmospheric atmospheric pressure at pressure at sea level at sea level at

00°°CC

PascalPascal PaPa SI Unit for SI Unit for Pressure 1 Pa Pressure 1 Pa

= 1N/m= 1N/m22

BarometersBarometers

LIQUIDS:LIQUIDS: Why are they the Why are they the least common state of matter?least common state of matter?

1. Liquids and K.M.T.1. Liquids and K.M.T. Are particles in constant motion? Are particles in constant motion?

Spacing?Spacing?

Kinetic Energy? Attractive forces?Kinetic Energy? Attractive forces? FluidFluid: a substance that flows and : a substance that flows and

hence takes the shape of its hence takes the shape of its container.container.

Properties of LiquidsProperties of Liquids

1.1. High DensityHigh Density: 1000x greater than : 1000x greater than gases, 10% less dense than solids.gases, 10% less dense than solids.

2.2. Relatively IncompressibleRelatively Incompressible: Water’s : Water’s volume only decreases 4% under volume only decreases 4% under 1000atm of pressure! 1000atm of pressure!

3.3. Can diffuse:Can diffuse:

Slower in liquids than gases due to:Slower in liquids than gases due to:

slower motion and attractive forces.slower motion and attractive forces.

Atmospheric Pressure & Atmospheric Pressure & Boiling PointBoiling Point

• Evaporation (vaporization): Evaporation (vaporization): conversion of a liquid to a gas or vapor conversion of a liquid to a gas or vapor below its boiling point. below its boiling point.

• Vapor Pressure: Vapor Pressure: particles collide with particles collide with the walls of the sealed container. the walls of the sealed container. – Dynamic EquilibriumDynamic Equilibrium

• Boiling Point: Boiling Point: temp. at which the v.p. temp. at which the v.p. of the liquid is just equal to the external of the liquid is just equal to the external pressure. pressure.

Evaporation vs. Boiling Evaporation vs. Boiling

Phase Change DiagramsPhase Change Diagrams

You will see a heat curve for water in You will see a heat curve for water in the next slide.the next slide.

FREEZING, SOLIDIFICATION, CRYSTALLIZATION

MELTING

CONDENSATION

EVAPORATION, VAPORIZATION

DEPOSITION

SUBLIMATION

HEAT OF

FUSION80

cal/g

HEAT OF VAPORIZATION

540 cal/g

Solid

Liquid

Gas

FREEZING, SOLIDIFICATION, CRYSTALLIZATION

MELTING

CONDENSATION

EVAPORATION, VAPORIZATION

DEPOSITION

SUBLIMATION

HEAT OF

FUSION80

cal/g

HEAT OF VAPORIZATION

540 cal/g

Solid

Liquid

Gas