Kinetic Theory of Matter (KTM)

AKA: Kinetic Molecular Theory (KMT) Molecular Kinetic Theory (MKT)

Not associated with TKM—the international postal code for

Turkmenistan

Rule 1

• All matter is composed of particles in constant motion

Rule 2

• Temperature is a measure of the kinetic energy of the particles.

Rule 2 (a and b)

• Temperature is a measure of the kinetic energy of the particles.

a) When you heat a sample, the particles speed up

b) When you cool a sample the particles slow down

After that, things get hazy.

?

Consider the state:

• Solid Liquid Gas

Particles in motion:

• Solid Liquid Gas

Particles in motion:

• Solid Liquid Gas

Vibrating about a fixed

position

Particles in motion:

• Solid Liquid Gas

Moving over and around other particles,

unlikely to escape surface

Particles in motion:

• Solid Liquid Gas

Moving freely, colliding with other particles and the walls of container

Consider state changes:

Liquid

Solid GasSublimation

Boiling

, ev

apor

ation

,

vapo

rizat

ionFreezing

Melting

Conde

nsat

ion

Particles on particles:

• Solid Liquid Gas

Particles not touching

Particles in contact

Particles in contact

This is huge. Really.

Values and preferred units

• P—atmospheres• T—kelvins• V—Liters• n—moles

Conversions

• P: 1 atm =760 mmHg=760torr=101.3 kPa=101,325

Pa

• T: T(k) = T(oC) + 273

• V: 1L=1000 ml=.001 m3

How fast do particles move?

It depends on:

How fast do particles move?

It depends on:

• Temperature:

• Size of the particle:

How fast do particles move?

It depends on:

• Temperature: High T faster motion

• Size of the particle: Smaller faster

Cool, medium, warm

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

What about water?

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

What about water?

Water melts / freezes

Water boils/ condenses

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

What about water?

Water is a solid

Water is a liquid

Water is a gas

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

What about water?

Water is a solid

Water is a liquid Water is

a gas

Increasing pressure will

melt ice

Decreasing pressure will

boil water

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

What about water?

Water is a solid

Water is a liquid Water is

a gas

Sublimation occurs at low T and P

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

What about water?

Water is a solid

Water is a liquid Water is

a gas

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

Describe these processes

A

H

D

B

IG

E

C

F

Water is a solid

Water is a liquid

Water is a gas

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

Describe these processes

Heating curve lab

Vacuum pump demo

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

Water

Normal boiling point

Normal melting point

Triple point

Phase diagrams

T

P

0 k

0 atm

1 atm

273 k 373 k

Water

Critical pressure

Phase diagrams

T

P

0 k

0 atm

Most other substances

Critical pressure

Critical temperature

The phase diagram for water

Phase diagrams

T

P

0 k

0 atm

1 atm

Phase diagrams

T

P

0 k

0 atm

Critical pressure

Critical temperature

1 atm

The phase diagram for CO2

The phase diagram for water

Can you explain why each of these phenomena occurs?

Thermal expansion of a solid—solids expand when heated

Thermal expansion of a liquid –liquids expand when heated

Thermal expansion of a gas –gasses expand when heated

Can you explain why each of these phenomena occurs?

Compressibility of gasses—gasses can be compressed into a smaller volume

Incompressibility of liquids –liquids can’t be compressed into a smaller volume

Incompressibility of solids –solids can’t be compressed into a smaller volume

Can you explain why each of these phenomena occurs?

Conduction of heat between two objects in contact—the cool one warms up.

Heat flow stops when temperatures are equal

Can you explain why each of these phenomena occurs?

Fluidity of gasses—gasses flow, they have no fixed shape

Fluidity of liquids—liquids flow, they have no fixed shape

Rigidity of solids—solids do not flow, they have a fixed shape

Can you explain why each of these phenomena occurs?

Melting point of a solid —at a certain temperature, a solid changes into a liquid

Boiling point of a liquid —at a certain temperature, a liquid changes into a gas

Freezing point of liquids –at a certain temperature, a liquid changes into a solid

Melting is endothermic (requires heat)Boiling is endothermic (requires heat)

Can you explain why each of these phenomena occurs?

Liquification of gasses is accomplished at low temperatures and high pressures

Sublimation of solids (to gas) at low pressures

Sublimation of solids (to gas) at high temperatures

Evaporation cools a liquidYou can see your breath on a cold day

Can you explain why each of these phenomena occurs?

Boyle’s Law —when the volume of a gas is reduced, its pressure increases

Charles’ Law —when gasses are cooled, their volumes act as if they will reach zero volume at a temperature of absolute zero

Avogadro’s Law —identical volumes of gasses contain the same number of particles

Graham’s law —heavier gasses diffuse slowerDalton’s law of partial pressures —the total

pressure of a mixture of gasses is the sum of the pressures of each gas.

Can you explain why each of these phenomena occurs?

Decrease in boiling point of a liquid with lower pressure

Increase in boiling point when solutes are added to a solvent

Decrease in freezing point when solutes are added to a solvent

Metals conduct heat better than other solids