Chemistry 101 - Section H
Solids, Liquids, and Especially
Gases
• This presentation was created by
Professor Carl H. Snyder
Chemistry Department
University of Miami
Coral Gables, FL 33124
CSnyder@miami.edu
• Copyright 2003 by Carl H. Snyder,
University of Miami. All rights reserved.
Chapter 12 - Solids, Liquids,
and Especially Gases
Solids, Liquids, and Gases
• Solids - maintain
their own volumes
and shapes
• Liquids - maintain
their own volumes
but take the shapes
of their containers
• Gases - maintain
neither their own
volumes nor shapes,
but take both the
volumes and shapes
of their containers.
Why Solids Melt, Liquids Boil
• When we heat a substance, we add energy to
its chemical particles.
• This energy makes their particles move,
vibrate, rotate, etc., faster … in every way.
Melting
Point
• Melting - Solid to
liquid
• Freezing - Liquid
to solid
Boiling Point
• Boiling - Liquid to gas throughout the entire
mass of the liquid.
• Evaporation - Liquid to gas only at the
surface
• Condensation - Gas to liquid
Evaporation
• Evaporation occurs
when molecules with
high translational
energies escape from
the surface of the
liquid.
• Evaporation can occur
at temperatures far
below the boiling point
Sublimation
• The disappearance of snow at temperatures
too cold for melting to occur takes place
through sublimation.
The Gas We Live In
The Composition of Dry Air
• Dry air is
roughly 80%
N2, 20% O2,
and traces
of other
gases.
Atmospheric Pressure
• The total mass of all the
atmosphere above any
give point on or above
the earth’s surface
produces the
atmospheric pressure
at that point.
Measuring Atmospheric
Pressure
• The barometer, an
instrument for
measuring
atmospheric
pressure
• Invented by
Evangelista
Torricelli
• 1643
The Kinetic-Molecular Theory
• What happens when you pump up a tire -- and
much more -- is explained by the kineticmolecular theory of gases.
• Kinetic (moving) molecular (molecules) =
moving molecules.
The Basis of The Kinetic-Molecular
Theory
• All gases are
composed of atoms or
molecules that are in
constant motion,
richocheting off each
other and off walls like
billiard balls.
• The higher the
temperature, the faster
the atoms or moleucles
move.
The Cast of Characters
• Each of these scientists contributed to our
understanding of the behavior of gases.
Robert Boyle
A Statement of Boyle’s Law
Illustrations of Boyle’s Law
• Double the pressure on a fixed quantity of
gas held at constant temperature, and its
volume decreases to half.
Boyle’s Law and The KineticMolecular Theory of Gases
• As we decrease the
volume of a constant
quantity of gas
molecules (kept at
constant temperature),
the moving molecules
hit the sides of their
container more often.
• This results in a higher
pressure.
Jacques Alexandre Cesar
Charles
• Q: But . . . what value of temperature shall we
use?
• A: The Kelvin temperature.
William Thomson, Lord Kelvin
• William Thomson,
Lord Kelvin, gave us
the Kelvin
temperature scale.
• The Kelvin
temperature scale
begins at absolute
zero and move
upward in degrees
the same size as
those of the Celsius
scale.
Charles’ Law and The KineticMolecular Theory of Gases
• As we decrease the
temperature, the gas
molecules move with
less energy.
• If we keep the
pressure constant, the
volume of the gas
decreases.
Can the Volume of a Gas
Drop to Zero?
• No, because
the gas laws
apply strictly
only to ideal
gases.
• A real gas will
condense to a
liquid before it
reaches
absolute zero.
Combining Boyle’s Law and
and Charles’ Law
• Combining Boyle’s Law and Charles’ Law, we
get the combined gas law equation.
• P1 V1 and T1 apply to one set of condition, P2
V2 and T2 apply to a second set of conditions.
Joseph Louis Gay-Lussac
• Gay-Lussac’s Law can be restated to: When
gases react with each other, the ratio of their
reacting volumes is the same as the ratio of
their reacting molecules.
Amedeo Avogadro
• At a constant pressure and temperature, the
volume a gas occupies is directly proportional
to the number of molecules (or number of
moles) of the gas that’s present.
• This is the same Avogadro who gave us
Avogadro’s number
Demonstrating Avogadro’s
Law
• Blow into a balloon (increase the value of n)
and the balloon gets larger (the value of V
increases).
John Dalton
• The total pressure of all the gases in a
mixture of several gases is the sum of the
pressures exerted by each of the individual
gases -- the sum of their individual partial
pressures.
The Partial Pressures of the
Air We Breathe
• Notice that the sum of these partial pressures
is 760 mm-Hg, which is our standard
atmospheric pressure.
William Henry
• If the partial pressure of a gas above a liquid is low,
very little of the gas dissolves in the liquid.
• If the partial pressure of a gas above a liquid is high,
plenty of the gas dissolves in the liquid.
• We can describe the concentration of the
dissolved gas in the liquid by using the partial
pressue of the gas above the liquid.
The Laws of a Bottle of Soda
Part I
The Laws of a Bottle of Soda
Part II
The Art and Science of Breathing
• We metabolize glucose (and other nutrients)
for energy.
• Body cells require O2 as a reactant.
• Body cells produce CO2 as a product.
• Our blood must supply oxygen and remove
carbon dioxide.
• The gas laws come into play in the process.
The Physiology of the Lungs
Blood Transports O2 and CO2
Between the Alveolae and the
Cells
Partial Pressures of Blood
Gases
End - Chapter 12