Gases, Liquids and Solids Flashcards
When all the molecules
of a system become motionless and line up perfectly, we achieve
the greatest possible order.
entropy
Kinetic energy increases with
increasing temperature.
true
At high temperatures, molecules possess a high kinetic energy and move
so fast that the attractive forces between them are too weak to hold them
together. This situation is called the
gaseous state
At lower temperatures,
molecules move more slowly, to the point where the forces of attraction
between them become important. When the temperature is low enough, a gas
condenses to form a
liquid state
When the temperature is even lower, molecules no longer have enough
velocity to move past each other.
solid state
each molecule has a certain number of nearest neighbors, and these neighbors do not change
solid state
Typically a solid,
when heated to a sufficiently high temperature, melts and becomes a liquid.
The temperature at which this change takes place is called the
melting point
Further heating causes the temperature to rise to the point at which
the liquid boils and becomes a gas. This temperature is called the
boiling point
The force per unit area
exerted against a surface
pressure
Instrument used to measure atmospheric pressure
barometer
Pressure is most commonly measured in
mmHg
Pressure is also measure in torr, a unit named in honor of
Evangelista Torricelli
At sea level, the average pressure of the
atmosphere is
760 mmHg
A barometer is adequate for measuring the pressure of the atmosphere,
but to measure the pressure of a gas in a container, we use a simpler instrument called a
manometer
states that for a fixed mass of gas at a constant temperature, the
volume of the gas is inversely proportional to the pressure.
Boyle’s Law
P1V1 = P2V2
Boyle’s Law
states that the volume of a fixed mass of gas at a constant
pressure is directly proportional to the temperature in kelvins (K).
Charles’ Law
(V1/T1) = (V2/T2)
Charles’ Law
states that, for a fixed mass of a gas at constant volume,
the pressure is directly proportional to the temperature in kelvins (K)
Gay-Lussac’s Law
(P1/T1) = (P2/T2)
Gay-Lussac’s Law
The three gas laws can be combined and expressed by a mathematical
equation called the
Combined gas law
(P1V1/T1) = (P2V2/T2)
Combined gas law
Equal volumes
of gases at the same temperature
and pressure contain the same
number of molecules
Avogadro’s Law
Standard pressure
1atm
Standard Temperature
0°C
Avogadro’s law allows us to write a gas law that is valid not only for any
pressure, volume, and temperature, but also for any quantity of gas. This
law, called
ideal gas law
states that the total
pressure, PT, of a mixture of gases is the sum of the partial pressures of each
individual gas
Dalton’s law of partial pressure
is the pressure that the gas would exert if it were alone in the container
Partial pressure
The relationship between the observed behavior of gases and the behavior of individual gas molecules within the gas can be explained by the
kinetic molecular theory
Assumptions of kinetic molecular theory
- Gases consist of particles, either atoms or molecules, constantly moving
through space in straight lines, in random directions, and with various
speeds.
2.The average kinetic energy of gas particles is proportional to the temperature in kelvins. - Molecules collide with each other but the total kinetic energy of the gas sample remains the same.
- Gas particles have no volume.
- There are no attractive forces between gas particles.
- Molecules collide with the walls of the container, and these collisions
constitute the pressure of the gas. The greater the number of collisions
per unit time, the greater the pressure.
change from a gas to a
liquid
condensation
change from a liquid to a solid
solidification
three types of intermolecular forces
London
dispersion forces, dipole–dipole interactions, and hydrogen bonding
Extremely weak attractive forces
between atoms or molecules
caused by the electrostatic
attraction between temporary
induced dipoles
London dispersion forces
He first explained the London dispersion forces
Fritz London
The attraction
between the positive end of one dipole and the negative end of another
dipole is called a
dipole-dipole interaction
These interactions can exist
between two identical polar molecules or between two different polar molecules
dipole-dipole interaction
When
the positive end of one dipole is a hydrogen atom bonded to an O or N and the negative end of the other
dipole is an O or N atom, the attractive interaction between dipoles is particularly strong and is given a special name:
hydrogen bond
is directly related to the
strength of the intermolecular attraction between its molecules.
surface tension
An important property of liquids is their tendency to evaporate.
vapor pressure
A condition in which
two opposing physical forces are
equal
equilibrium
The pressure of a
gas in equilibrium with its liquid
form in a closed container
vapor pressure
is the temperature at which its vapor pressure is equal to the pressure of the atmosphere in contact with its surface
boiling point
The boiling point when the atmospheric pressure is 1 atm is called the
normal boiling point
the boiling point of covalent compounds depends primarily on three factor
- Intermolecular forces
- Number of sites for intermolecular interaction
- Molecular shape
Formation of a solid from a liquid is called
solidification or crystallization
Types of solids
Ionic, Molecular, Polymeric, Network and Amorphous
Solids made up of ions in a crystal lattice
Ionic
Solids made up of molecules in a crystal lattice
Molecular
Solids made up of giant molecules; can be crystalline, semi-crystalline or amorphous
Polymeric
Solids made up of a very large number of atoms connected by covalent bonds
Network
Solids made up of randomly arranged atoms or molecules
Amorphous
is the fifth form of solid carbon
Soot
A change from
one physical state (gas, liquid,
or solid) to another
Phase change
is any part
of a system that looks uniform (homogeneous) throughout
phase
The heat necessary to melt 1.0 g of
any solid is called its
Heat of fusion
The heat of fusion of ice is
80 cal/g
The specific heat of liquid water is
1 cal/g °C
The amount of heat necessary to vaporize 1.0 g of a liquid at its normal boiling point is called its
heat of vaporization
Heat of vaporization of water
540 cal/g
The specific heat of steam
0.48 cal/g
The data for
heating 1.0 g of water from 220°C to 120°C can be shown in a graph called
heating curve
A transition from the solid state directly into the vapor state without
going through the liquid state is called
sublimation
We can show all phase changes for any substance on a
phase diagram
At a unique point (A) on the phase diagram, called the ______, all three phases coexist.
triple point
We live at the bottom of an ocean of air whose composition by volume is roughly ___ N2, _____ O2, and ______ other gases, including CO2
78%, 21%, 1%
the nature and magnitude of the attractive forces among the molecules
intermolecular forces
Characteristics of gases
- Gases assume the volume and shape of their containers.
- Gases are the most compressible of the states of matter.
- Gases will mix evenly and completely when confined to the same container.
- Gases have much lower densities than liquids and solids.
is defined as the change in distance with elapsed time
velocity
is the change in velocity with time
Acceleration
The second law of motion, formulated by Sir Isaac Newton† in the late seventeenth century, defines another term, from which the units of pressure are derived
Force
SI unit of force
Newton
force applied per unit area
Pressure
SI unit of pressure, defined as one newton per square meter
Pascal
the pressure exerted by Earth’s atmosphere
Atmospheric pressure
two types of manometer
Closed-tube manometer and open-tube manometer
is normally used to measure pressures below atmospheric pressure
closed-tube manometer
suited for measuring pressures equal to or greater
than atmospheric pressure
open-tube manometer
Nearly all barometers and most manometers use ______ as the working fluid
mercury
the proportionality constant
gas constant
describes the relationship among the four variables
P, V, T, and n
ideal gas equation
a hypothetical gas whose pressure-volume-temperature
behavior can be completely accounted for by the ideal gas equation
ideal gas
a dimensionless
quantity that expresses the ratio of the number of moles of one component to the number of moles of all components present
mole fraction
SI unit of energy
Joule
a number of generalizations about gas behavior
Kinetic molecular theory of gases
They found kinetic molecular theory of gases
Maxwell, Boltzmann and others
is the result of collisions
between molecules and the walls of their container.
Gas pressure
the speed of the largest number of molecules
most probable speed
an average molecular speed
root mean square speed
the gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties
Diffusion
Buckminster Fuller (1895–1983) invented domes of a similar structure (he
called them geodesic domes), the C-60 substance was named
buckminsterfullerene or buckyball
a homogeneous
part of the system in contact with other parts of the system but separated from them
by a well-defined boundary
phase
attractive forces between molecules
intermolecular forces
hold atoms together in
a molecule
intramolecular forces
attractive forces between polar molecules
dipole-dipole forces
attract an ion (either a cation
or an anion) and a polar molecule to each other
ion-dipole forces
the separation of positive and negative charges in the
atom (or nonpolar molecule) is due to the proximity of an ion or a polar molecule
induced dipole
attractive interaction between an ion and the induced dipole is called
ion-induced dipole interaction
attractive interaction between a polar molecule and the induced dipole is called
dipole-induced dipole interaction
At any instant it is likely that the atom has a dipole moment created
by the specific positions of the electrons. This dipole moment is called an
instantaneous dipole
attractive forces that arise as a result of temporary dipoles induced in
atoms or molecules
dispersion forces
A quantum mechanical interpretation of temporary dipoles was provided by
Fritz London
special type of dipole-dipole interaction between the hydrogen atom in a polar bond, such as NOH, OOH, or FOH, and an electronegative O,
N, or F atom.
Hydrogen bond
the amount of energy required to stretch or increase the surface of a liquid by a unit area
surface tension
the intermolecular attraction between like molecules
cohesion
an attraction between unlike molecules
adhesion
a measure of a fluid’s resistance to flow
viscosity
possesses rigid and long-range order; its atoms, molecules, or ions occupy specific positions
Crystalline solid
basic repeating structural unit of a crystalline solid
unit cell
Each sphere represents an atom, ion, or molecule and is called a
lattice point
the number of atoms (or ions) surrounding an atom (or ion) in a crystal lattice
coordination number
he most efficient arrangement
of spheres
closest packing
the scattering of X rays by the units of a crystalline
solid
x-ray diffraction
an optically transparent fusion product of inorganic materials that has cooled to a rigid
state without crystallizing
Glass
process in which a liquid is transformed into a gas
Evaporation
the rate of a forward process is exactly balanced by the rate of the reverse process, is reached when the rates of condensation and evaporation become equal
Dynamic equilibrium
the vapor pressure measured when a dynamic equilibrium exists between condensation and
evaporation
equilibrium vapor pressure
the energy (usually in kilojoules) required to vaporize
one mole of a liquid
molar heat of vaporization
which its gas phase cannot be made to liquefy, no matter how great the applied pressure. This is also the highest temperature at which a substance can exist as a liquid
critical temperature
the minimum pressure that must
be applied to bring about liquefaction at the critical temperature
critical pressure
a liquid can be temporarily cooled to below its freezing point
supercooling
molecules make the transition from vapor to solid directly
Deposition
the energy (usually in kilojoules) required to sublime
one mole of a solid
= Hfusion + Hvaporization
Molar heat of sublimation
