The States of Matter

1
Chapter 9

• The States of Matter

2
Kinetic Theory

• Kinetic Energy 1. energy of motion, 2.
  particles are in motion, 3. energy the substance
  has because of its motion.
• Kinetic Theory the tiny particles in all forms
  of matter are in constant motion.

3
Three major points

• 1. All matter is made up of tiny particles,
  which are always moving.
• 2. The higher the temperature, the faster the
  particles move.
• 3. At a given temperature, lighter particles
  move faster than heavier ones.

4
The States of Matter

• The state a substance is in depends on how the
  particles, which make it up, are moving.
• Solids (s) fixed shape and volume
• Liquids (l) fixed volume, takes shape of its
• container
• Gas (g) no fixed shape or volume
• Plasma very high energy gases in which some or
  all of the electrons are removed from the atoms
  or molecules.
• (In chemistry we tend to ignore plasmas,
  leaving them to the realm of the physicists,)

5
Using this theory as a model, we can explain many
things. Let us consider how the particles are
arranged in the 3 states of matter. (phases)
Particles have slightly more energy so are able
to move randomly around each other and are spaced
slightly further than in a solid. However they do
not have sufficient energy to overcome the
attractive forces between them so cannot from
each other escape completely.
Particles arranged in a regular, close-packed
fashion. They have little energy, so simply
vibrate about fixed positions, unable to overcome
the attractive forces between them.
Particles have much more energy so have overcome
all attractive forces between them. They move
around very fast in a random fashion, colliding
occasionally. They are much more spread out then
in the solid or liquid state
6
Gases

• A gas is composed of particles, usually molecules
  or atoms.
• Between the particles is empty space.
• No attractive or repulsive forces exist between
  particles.
• Uncontained gases diffuse into space without
  limit.

7
Gases cont.

1. The particles in a gas move rapidly in constant
   random motion.
2. All collisions are perfectly elastic. Kinetic
   energy is completely transferred from one
   particle to another. No absorption of the energy
   by containers, etc.

8
Gas Dependencies

• Gas Pressure result of simultaneous collisions
  of billions upon billions of gas particles with
  an object.
• Increase or decrease in pressure is indirectly
  proportional to the space between the molecules
  or atoms. ( decreasing space, increases pressure)

9
Gas Numbers to Know

• SI unit for pressure Pa Pascal
• Atmospheric Pressure at Sea level 101.32kPa
• One standard Atmosphere (1atm) the pressure
  required to support 760mm of mercury at 25oC.
• STP standard temperature and pressure 0oC
  and 1atm or 101.32kPa or 760mm/Hg

10
Liquids

• Particles in motion, free to slide past one
  another. Gases Liquids flow and are considered
  to be fluids.
• Intermolecular forces are greater than that of
  gases and the particles spin and vibrate in fixed
  positions while moving from place to place.

Solids

• Vibrate around a fixed position
• Particles are tightly packed in highly organized
  patterns.
• Denser than liquids and gases and can not be
  compressed.

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State Changes or Phase Change

• When a substance changes state, it is undergoing
  a physical change, there is no new substance
  formed. Physical changes unlike chemical changes
  are easy to reverse.
• Energy is required to turn from solids to
  liquids, and liquids to gases. In order to gain
  greater freedom of movement, the forces between
  the particles must be overcome.
• Energy is given up as gases turn to liquids, and
  liquids to solids. They move less freely and are
  held together more strongly.

12
State or Phase Change Terminology

• Evaporation (vaporization) conversion of a
  liquid to a gas or vapor below its boiling point
• Condensation conversion of a gas to a liquid
• Melting conversion of a solid to a liquid
• Freezing conversion of a liquid to a solid
• Sublimation conversion of a solid directly to a
  gas with no liquid formation.
• Deposition conversion of a gas directly to a
  solid with no liquid formation. (formation of
  frost)

13
Changes of State

freezing
14
Temperature Change Terminology

• The following are considered to be the
  temperature at which the state or phase change
  occurs at
• Melting point (mp) - Freezing point (fp)
• Boiling point (bp) condensing point
• What is boiling?
• Temperature at which the vapor pressure of the
  liquid equals the external pressure
• Boiling temperature changes with external
  pressure changes. (e.g. sea level 1000C, atop Mt.
  Everest 700C for water)