Transcript Modern Chemistry Chapter 10 States of Matter

Modern Chemistry
Chapter 10
States of Matter
Kinetic-Molecular Theory
• The kineticmolecular theory of
matter is based on
the idea that particles
of matter are always
in motion and this
motion has
consequences that
affect its physical
properties.
Kinetic-Molecular Theory of Gases
• 1- Gases consist of large numbers of tiny
•
•
•
•
particles that are far apart relative to their size.
2- Collisions between gas particles and
between particles and their container walls are
elastic. An elastic collision is one in which
there is no net loss of total kinetic energy.
3- Gas particles are in continuous, rapid,
random motion. They therefore possess kinetic
energy (energy in motion).
4- There are no forces of attraction between gas
particles.
5- The temperature of a gas depends upon the
average kinetic energy of the particles of the
gas.
Gases have indefinite shape and
indefinite volume.
The Kinetic-Molecular Theory and the Nature of Gases
• EXPANSION- Gases do not have definite shape or volume.
They expand to completely fill any container.
• FLUIDITY- Gases flow so they are fluids.
• LOW DENSITY- The density of a gas is about 1/1000 that of
the same substance in the liquid state.
• COMPRESSIBILITY- Gases can be compressed (the
volume decreases) by applying pressure to the gas.
• DIFFUSION- Gases have the ability to spread and mix with
one another due to the random motion of their particles.
• EFFUSION- A process by which gas particles under
pressure pass through a tiny opening from one container to
another.
Section 2-
LIQUIDS
• A LIQUID is a substance that has definite
volume but indefinite shape (it takes the
shape of its container).
• Liquids are fluids because they have the
ability to flow from one container to
another and take the shape of the new
container.
Properties of Liquids
• 1- Liquids have a high density relative to gases. Their
density is about 1000 x that of the gas of the same
substance.
• 2- Liquids are relatively not compressible.
• 3- Liquids have the ability to diffuse.
• 4- Liquids exhibit surface tension, a force that tends to
pull adjacent parts of a liquid’s surface together, thereby
decreasing the surface area to its smallest possible size.
Surface tension resists penetration of objects into a
liquid.
• 5- Liquids have capillary action, the attraction of the
surface of a liquid to the surface of a solid.
Changes of Physical State
• vaporization is the process by which
a boiling liquid changes to a gas
• evaporation is the process by which
particles escape from the surface of
a non-boiling liquid and enter the gas
state
• boiling is the change of a liquid to
bubbles of vapor that appear
throughout the liquid
• freezing (solidification) is the
physical change of a liquid to a solid
by the removal of heat energy
Section 3
SOLIDS
• solids have a definite shape
and a definite volume
• crystalline solids consist of
crystals, a substance in which
the particles are arranged in an
orderly, geometric, repeating
pattern
• amorphous solids consist of
particles that are randomly
arranged
Properties of Solids
1- DEFINITE SHAPE & VOLUME
2- DEFINITE MELTING POINT
melting is the physical change from a solid to a
liquid by the addition of heat
melting point is the temperature at which a solid
becomes a liquid
supercooled liquid is a substance that retains
certain properties of a liquid even at
temperatures where it appears to be a solid
(glass, plastics,…)
3- HIGH DENSITY (10x a liquid & 10,000x a gas)
4- INCOMPRESSIBILITY
5- LOW RATE OF DIFFUSION
Crystalline Solids
crystal structure is the total threedimensional arrangement of particles of a
crystal
crystal lattice is the representation of the
arrangement of a crystal using a
coordinate system
unit cell is the smallest portion of a crystal
lattice that shows the three-dimensional
pattern of the entire lattice
Types of Crystals
1) ionic crystals consist of positive & negative
ions arranged in a regular pattern such as
NaCl (salt) crystals
2) covalent network crystals consists of atoms
covalently bonded to their adjacent atoms such
as diamonds & SiO2 (sand)
3) metallic crystals consists of metal cations
surrounded by delocalized valence electrons
4) covalent molecular crystals consists of
covalently bonded molecules held together by
intermolecular forces
Amorphous Solids
• Glass is made by cooling molten materials
in a way that prevents them from
crystallizing. This allows the glass to
appear to be a solid yet be transparent.
• Other examples include plastics and
semiconductors (used in electronics).
Section 4-
Changes of State
1- The three most recognized physical states of matter are solid,
liquid, & gas.
2- A phase is any part of a system that has uniform composition
and properties.
3- When a substance changes its physical state is called a
phase change.
• Condensation is the process by which a gas changes to a
liquid.
• Equilibrium is a condition in which two opposing changes
occur at equal rates (eg. liquid to gas = gas to liquid)
• Equilibrium vapor pressure is the pressure exerted by a
vapor in equilibrium with its corresponding liquid at a given
temperature.
• Volatile liquids are liquids that evaporate easily.
Boiling
• Boiling is the conversion of a liquid to a vapor (gas)
throughout all parts of the liquid.
• Boiling point of a liquid is the temperature at which the
equilibrium vapor pressure of the liquid equals the
atmospheric pressure.
• Energy must be added continuously in order to keep a liquid
boiling.
• Molar enthalpy of vaporization ( ΔHv ) is the amount of
energy needed to vaporize one mole of a liquid at the liquid’s
boiling point under constant pressure.
• Heat of vaporization is the amount of heat needed to
vaporize one gram of a liquid at its boiling temperature.
• Heat of vaporization for water is 540 calories/gram.
Freezing & Melting
• Freezing is the physical change of a liquid becoming a
solid. Also called solidification or fusion.
• Freezing point is the temperature at which a liquid
becomes a solid and the solid and the liquid are at
equilibrium.
• Molar enthalpy of fusion ( ΔHf ) is the amount of
energy required to melt one mole of a solid at its melting
point.
• Heat of fusion is the amount of heat needed to melt one
gram of a solid.
• For ice, this is 80 calories/gram.
Other Changes of Physical State
• Sublimation is the process by
which a solid changes to a gas,
bypassing the liquid state.
• Examples include dry ice, moth
balls, iodine, and ice at
temperatures below 0°C.
• Deposition is the process by
which a gas changes directly to
a solid, bypassing the liquid
state.
• An example would be frost.
Phase Diagrams
• A phase diagram is a graph of pressure versus temperature that shows the
conditions under which the phases of a substance exist.
• The triple point of a substance indicates the temperature and the pressure
conditions at which the solid, liquid, and vapor of the substance can coexist
at equilibrium.
• The critical point of a substance indicates the critical temperature and
pressure
• The critical temperature is the temperature above which a substance
cannot exist in the liquid state.
• The critical pressure is the lowest pressure at which a substance can exist
as a liquid at the critical temperature.
• Please see figure 16 on page 347 of the textbook.
• Use figure 16 to answer section review question #7 on page 348 of the
textbook.
Section 5- Water
• Hydrogen bonding in water molecules make water a
unique substance. Without hydrogen bonding, water
would be a gas at room temperature.
• Hydrogen bonding allows water to form crystals when it
freezes.
• Due to the crystal structure of ice, it is less dense than
liquid water and will float.
• Floating ice acts as insulation to water below.
• If ice sank rather than floated, water would turn to solid
ice in temperate climates and most of the living
organisms in the water would die. Can you say frozen
fish sticks?
Water
• Water freezes at 0°C and boils at 100°C.
• The molar enthalpy of fusion for water is
6.009 kJ/mol at one atmosphere of
pressure.
• The molar enthalpy of vaporization for water
is 40.79 kJ/mol at one atmosphere of
pressure.
• Do practice problems #1 & #2 on page 351.
Questions about water.
1.
Why are there more orchards, vineyards, and
vegetable farms near Lake Erie than in central Ohio?
2.
Why does steam cause more severe burns than
boiling water?
3.
Why do we use ice cubes?
4.
Why does snow at very low temperatures (dry snow)
contain less water than snow that falls at temperatures
around freezing (wet snow)?
5.
Why do we say that it takes about 7” of snow to equal
1” of water?
6.
What causes the frost on car windows?
Chapter 10 Test Review
•
25 multiple choice questions
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
definition & applications of the kinetic-molecular theory
why matter changes phase
definition of temperature
examples of gas diffusion & gas effusion
expansion & compression of gases
effects of intermolecular forces and their application to states of matter
compare density & the states of matter
definitions of vaporization, evaporation, & sublimation
motion of the particles of a sample of matter in the three physical states
properties of solids, liquids, & gases
compare crystalline vs. amorphous solids
definitions of crystal types & crystal lattice
definitions of triple point, volatile
factors that affect boiling
the boiling process
the density of ice versus water
temperature of greatest density of water
Honors Chemistry Chapter 10 Test
•
30 multiple choice questions
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
definition & applications of the kinetic-molecular theory
why matter changes phase
definition of temperature
examples of gas diffusion & gas effusion
expansion & compression of gases
effects of intermolecular forces and their application to states of matter
compare density & the states of matter
compare the energies of the phases of matter
definitions of vaporization, evaporation, & sublimation
motion of the particles of a sample of matter in the three physical states
properties of solids, liquids, & gases
compare crystalline vs. amorphous solids
definitions of crystal types & crystal lattice
definitions of triple point, volatile
factors that affect boiling
the boiling process
the density of ice versus water
temperature of greatest density of water
two calculations using molar enthalpies