States of MatterStates of Matter

Chemistry Joke

Once you’ve seen 6.02 x 1023 atoms…

You’ve seen a mole!

Kinetic TheoryKinetic Theory

Kinetic TheoryKinetic Theory explains the states of explains the states of matter based on the concept that the matter based on the concept that the particles in all forms of matter are in particles in all forms of matter are in constant constant motionmotion..

Kinetic TheoryKinetic TheoryGasesGases—particles are far —particles are far

apart with no attraction or apart with no attraction or repulsionrepulsion

LiquidsLiquids—particles can —particles can slide past one another but slide past one another but do experience attractiondo experience attraction

SolidsSolids—particles are not —particles are not free to move but tend to free to move but tend to vibrate about fixed pointsvibrate about fixed points

Kinetic Energy and Kinetic Energy and TemperatureTemperature

Directly RelatedDirectly Related

Increase TemperatureIncrease Temperature: : Molecules move faster. Molecules move faster.

Intermolecular forces can’t hold them together.Intermolecular forces can’t hold them together.

Decrease Temperature: Decrease Temperature: Molecules move slower.Molecules move slower.

Intermolecular forces can now hold them together.Intermolecular forces can now hold them together.

Absolute zero (0 K) is the temperature at which the Absolute zero (0 K) is the temperature at which the motion of particles theoretically ceases.motion of particles theoretically ceases.

The Nature of GasesThe Nature of Gases 33 basic assumptions of the kinetic theory basic assumptions of the kinetic theory

as it applies to gases:as it applies to gases:

#1.#1. Gas particles are s Gas particles are small, hard mall, hard spheres with no volume (compared to spheres with no volume (compared to the volume of the container) and the volume of the container) and experience no attraction or repulsion.experience no attraction or repulsion.

The Nature of GasesThe Nature of Gases

#2.#2. Particles in a gas move rapidly Particles in a gas move rapidly in constant in constant randomrandom motion but motion but always in straight paths, changing always in straight paths, changing direction only when colliding with direction only when colliding with one another or other objects.one another or other objects.

The Nature of GasesThe Nature of Gases

#3.#3. Collisions are perfectly Collisions are perfectly elastic. This means no kinetic elastic. This means no kinetic energy is lost when particles energy is lost when particles collide. collide.

An Early An Early BarometerBarometer

The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.

Barometers are used to measure atmospheric pressure.

The Nature of LiquidsThe Nature of Liquids

Unlike gas particles, liquid Unlike gas particles, liquid particles are attracted to each particles are attracted to each other, but they are still able to other, but they are still able to slide past one another. slide past one another.

The Nature of LiquidsThe Nature of Liquids The conversion of a liquid to a gas is The conversion of a liquid to a gas is

called called vaporization.vaporization. When this occurs at the When this occurs at the surfacesurface of a liquid of a liquid

that is not boiling, the process is called that is not boiling, the process is called evaporation.evaporation.

Volatile Volatile liquids evaporate at room temp.liquids evaporate at room temp. A liquid will evaporate faster when heatedA liquid will evaporate faster when heated

—more kinetic energy to overcome —more kinetic energy to overcome intermolecular forces.intermolecular forces.

But…But…evaporation is a evaporation is a cooling process cooling process because particles with the highest energy because particles with the highest energy escape 1escape 1stst! !

The Nature of LiquidsThe Nature of Liquids The The boiling pointboiling point (bp) is the (bp) is the

temperature at which the temperature at which the vapor vapor pressure of the liquid is equal to the pressure of the liquid is equal to the external pressure on the liquid.external pressure on the liquid.Bubbles form throughout the Bubbles form throughout the

liquid, rise to the surface, and liquid, rise to the surface, and escape into the air.escape into the air.

The Nature of LiquidsThe Nature of Liquids

Since the boiling point is where the Since the boiling point is where the vapor pressure equals external vapor pressure equals external pressure, the bp changes if the pressure, the bp changes if the external pressure changes.external pressure changes.

Normal Normal boiling point is the bp at boiling point is the bp at normal atmospheric pressure or normal atmospheric pressure or 1atm. 1atm.

The Nature of SolidsThe Nature of Solids

Most solids have particles packed Most solids have particles packed against one another in a highly against one another in a highly organized pattern.organized pattern. Tend to be dense and incompressibleTend to be dense and incompressible

The Nature of SolidsThe Nature of Solids When a solid is heated, the particles vibrate When a solid is heated, the particles vibrate

more rapidly as the kinetic energy increases.more rapidly as the kinetic energy increases. At some point, the disruptive vibrations are At some point, the disruptive vibrations are

strong enough to overcome the strong strong enough to overcome the strong interactions.interactions.

The The melting pointmelting point (mp) is the temperature a (mp) is the temperature a solid turns to liquid.solid turns to liquid.

The The freezing pointfreezing point (fp) is the same (fp) is the same temperature as the mp, but indicates the temperature as the mp, but indicates the liquid becoming a solid.liquid becoming a solid.

The Nature of SolidsThe Nature of Solids

Generally, most ionic solids have Generally, most ionic solids have high melting points, due to the high melting points, due to the relatively strong forces holding them relatively strong forces holding them together.together.

Molecular compounds have Molecular compounds have relatively low melting points.relatively low melting points.

Temperature

Pre

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SolidLiquid

Gas

1 Atm

Phase Diagram

Triple Point Normal

Boiling Point

Critical Point

Temperature

Solid Liquid

Gas

1 Atm

Pre

ssu

rePhase diagram

FREEZINGCONDENSATION

DEPOSITION

Temperature

SolidLiquid

Gas

1 Atm

Pre

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re

SUBLIMATION

MELTING

VAPORIZATION

Phase Diagram

Solid Air Fresheners!

Chemistry Joke

A photon checks into a hotel and is asked if he needs any help with his baggage.

No thanks, he says…

I’m travelling light!