Title: The States of Matter
1Chapter 9
2Kinetic 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.
3Three 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.
4The 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,)
5Using 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
6Gases
- 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.
7Gases cont.
- The particles in a gas move rapidly in constant
random motion. - All collisions are perfectly elastic. Kinetic
energy is completely transferred from one
particle to another. No absorption of the energy
by containers, etc.
8Gas 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)
9Gas 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
10Liquids
- 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.
11State 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.
12State 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)
13Changes of State
freezing
14Temperature 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)