Chapter 10
States of Matter
10.1 Kinetic Molecular Theory
(KMT)
“Particles of Matter are always in motion”
States of Matter
We will discuss the KMT in terms of :
1. Gases
2. Liquids
3. Solids
KMT - Gases
O Ideal gas- follows all of the tenets of the
KMT.
O 1. Gases consist of large numbers of
atoms/molecules that are in continuous,
random motion.
O 2. The combined volume of all the
atoms/molecules of the gas is negligible
relative to the total volume in which the gas is
contained.
Gases Cont.
O 3. Attractive and repulsive forces between
gas particles is negligible.
O 4. Energy can be transferred between
particles during collisions, but the average
kinetic energy of the particles does not
change with time (assuming temperature is
constant) = collisions are elastic
O 5. The average kinetic energy of the particles
is proportional to the absolute temperature.
O K.E. = ½ mv2
Properties of Gases
O Expansion-gases occupy the volume of the
container they are enclosed in.
O Fluidity- gas particles move like liquids
because there are no attractive or repulsive
forces among them
O Density- gases have low densities because
of the large amounts of space between the
particles.
Properties of Gases Cont.
O Compressibility- Gases can be easily
condensed with an increase in pressure due
to the large space between the particles.
O Diffusion- the random mixing of particles
due to their constant motion.
O Effusion- gas particles pass through a tiny
opening.
O Rate is directly proportional to the velocities
of the particles. (Smaller particles move
faster and vice-versa)
Real Gases
O Those that do not conform to the 5 parts of
the KMT.
O When gases are held at high pressure and
low temperatures they deviate from their
expected behavior.
O Noble gases conform the most to the KMT
and act like ideal gases.
O The more polar the gas molecule the more it
deviates from the KMT and acts like a real
gas.
10.2 Liquids
O Have a definite volume and take the shape
of its container
O Particles are closer together so their
attractive forces are stronger than in gases
(think strength of intermolecular forces)
O Fluid – the ability to flow and occupy the
shape of its container.
Liquids Cont.
O Density – fairly high considering the closer
arrangement of the particles
O Incompressibility- because of the close
proximity to one another, the particles in a
liquid can’t be pushed much closer together.
O Diffusion- liquids move easily among other
liquids. Attractive forces and temperature of
the particles lends to a slower diffusion rate
of the liquid particles.
Liquids Cont.
O Surface Tension- a force that attracts
adjacent particles on a liquids’ surface
together enough to decrease the surface
area.
O The higher the intermolecular forces the
higher the surface tension.
O Water has a fairly high surface tension.
Liquids Cont.
O Capillary Action – the attraction of the
surface of a liquid to the surface of a solid.
O Meniscus
O Chromatography
O Phloem tubes in plants
Liquids Cont.
O Vaporization – liquid changing to a gas
O Evaporation – vaporization at the surface of
a liquid
O Individual particles gain enough kinetic
energy to break the I.F. and escape as a gas.
O Freezing – liquid changing to a solid
O Due to the increased intermolecular
attractions among the particles
10.3 Solids
O Highly ordered arrangement with minimal
movement among the particles
O I.F. exert stronger forces due to this proximity
O Types:
O Crystalline- geometric, repeating pattern of
particles
O Amorphous- random arrangement of particles
O Glass, obsidian
O “without shape”
Solids Cont.
O Melting- changing a solid to a liquid by
applying heat energy
O Overcome I.F. and break apart from the
crystalline structure
O Supercooled liquids (amorphous solids) –
retain some liquid properties due to their
lack of a uniform, organized pattern
O High Density
O Low diffusion rate
Solids Cont.
O Types of Crystals (p. 340)
O 1. Ionic - NaCl
O 2. Covalent Network – SiO2
O 3. Metallic - Cu
O 4. Covalent Molecular – NH3
Changes of State
O Phase – when a substance has uniform
composition and properties
O Melting, freezing, vaporization, condensation,
sublimation, deposition
O Equilibrium – when two phases occur at the
same rate. E.g., melting
freezing
Changes of State Cont.
O Equilibrium Vapor Pressure – the pressure
exerted by a vapor in equilibrium with its
liquid at a given temp.
O Proportional to the concentration of
molecules in the vapor phase.
O Increases with an increase in temperature
O Volatile liquids (those that evaporate easily)
have higher V.P. because they tend to have
weaker I.F. between the molecules.
O Vapor Pressure Animation
Changes of State Cont.
O Boiling – change of a liquid to vapor at the
surface and within the liquid.
O Boiling point – when the V.P. equals the
atmospheric pressure.
O Normal B.P. of water = 100oC, (normal
atmospheric pressure of 1 atm, 760 torr,
101.3 kPa)
O B.P. Animation
Vapor Pressures of Various
Substances
Identity of Substances
O A – Diethyl ether
O B – Benzene
O C - water
Phase Diagrams
O Phase Diagram Explanation
Phase Diagram for Water