States of Matter

Chemistry Joke

Once you’ve seen 6.02 x 1023

atoms…

You’ve seen a mole!

Kinetic Theory

Kinetic Theory explains the states of

matter based on the concept that the

particles in all forms of matter are in

constant motion.

Kinetic Theory Gases—particles are far apart with

no attraction or repulsion

Liquids—particles can slide past one another but do experience attraction

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

Kinetic Energy and Temperature

Directly Related

Increase Temperature: Molecules move faster.

Intermolecular forces can’t hold them together.

Decrease Temperature: Molecules move slower.

Intermolecular forces can now hold them together.

Absolute zero (0 K) is the temperature at which the

motion of particles theoretically ceases.

The Nature of Gases

3 basic assumptions of the kinetic theory

as it applies to gases:

#1. Gas particles are small, hard spheres with no volume (compared to

the volume of the container) and

experience no attraction or repulsion.

The Nature of Gases

#2. Particles in a gas move rapidly

in constant random motion but

always in straight paths, changing

direction only when colliding with

one another or other objects.

The Nature of Gases

#3. Collisions are perfectly

elastic. This means no kinetic

energy is lost when particles

collide.

The Nature of Gases

Gas pressure is the force exerted by a

gas per unit surface area.

This pressure results from the

collisions of gas particles with objects.

The SI unit of pressure is the pascal (Pa)

1 atm = 760 mm Hg (or torr) = 101.3 kPa

An Early

Barometer

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 Plasma

Gas becomes plasma when

exposed to enough energy to cause

a significant number of atoms to

lose some or all of their electrons.

Those atoms become positive, and

the released electrons are free to

move about.

The Nature of Liquids

Unlike gas particles, liquid

particles are attracted to each

other, but they are still able to

slide past one another.

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

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

that is not boiling, the process is called evaporation.

Volatile liquids evaporate at room temp.

A liquid will evaporate faster when heated—more kinetic energy to overcome intermolecular forces.

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

The Nature of Liquids

The boiling point (bp) is the

temperature at which the vapor

pressure of the liquid is equal to the

external pressure on the liquid.

Bubbles form throughout the

liquid, rise to the surface, and

escape into the air.

The Nature of Liquids

Since the boiling point is where the

vapor pressure equals external

pressure, the bp changes if the

external pressure changes.

Normal boiling point is the bp at

normal atmospheric pressure or

1atm.

The Nature of Solids

Most solids have particles packed

against one another in a highly

organized pattern.

Tend to be dense and incompressible

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

more rapidly as the kinetic energy increases.

At some point, the disruptive vibrations are

strong enough to overcome the strong

interactions.

The melting point (mp) is the temperature a

solid turns to liquid.

The freezing point (fp) is the same

temperature as the mp, but indicates the

liquid becoming a solid.

The Nature of Solids

Generally, most ionic solids have

high melting points, due to the

relatively strong forces holding them

together.

Molecular compounds have

relatively low melting points.

Temperature

Pre

ssu

re

Solid Liquid

Gas

1 Atm

Phase Diagram

Triple

Point Normal

Boiling

Point

Critical

Point

Temperature

Solid Liquid

Gas

1 Atm

Pre

ssu

re Phase diagram

FREEZING CONDENSATION

DEPOSITION

Temperature

Solid Liquid

Gas

1 Atm

Pre

ssu

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!