Chapter 11 Flashcards
The vapor pressure of a liquid at a particular temperature is the
the partial pressure of the vapor over the liquid measured at equilibrium.
The vapor pressure depends on the
liquid and on the temperature.
boiling point
the temperature at which the vapor pressure is equal to the pressure on the liquid, usually atmospheric pressure. At this temperature, bubbles of gas form within the liquid.
The normal boiling point is measured at
1-atmosphere pressure.
When the pressure on the liquid increases, as is the case with a pressure cooker, the boiling point
increases
when the pressure on the liquid decreases, as is the case at high altitude, the boiling point
decreases
freezing point
the temperature at which a pure liquid changes to a crystalline solid (or freezes)
melting point
the temperature at which a crystalline solid changes to a liquid (or melts).
heat of fusion
the heat needed to melt a solid. It is given in kJ/mol
heat of vaporization
the heat needed to vaporize a liquid. It is given in kJ/mol
The Clausius–Clapeyron equation
can be used to find the vapor pressure, the heat of vaporization, or the temperature.
phase diagram
graphical way to summarize the conditions under which the various states of a substance are stable. •In a phase diagram, phases are separated by lines that represent equilibrium between those phases
triple point
the point where all three phases are in equilibrium.
critical point
gives the temperature (critical temperature, TC) at which the liquid state can no longer exist and the pressure at that temperature (critical pressure). Above this temperature and pressure, there is only one state, a supercritical fluid.
Surface tension
the energy required to increase the surface area of a liquid by a unit amount. The values are given in J/m2.
Surface tension arises because
the molecules at the surface of a liquid experience a net force toward the center of the liquid.
is the property that allows insects to walk on the surface of water or a pin to float
surface tension
viscosity
is the resistance to flow exhibited by liquids and gases
the 3 types of intermolecular forces
Dipole-Dipole forces, London forces, Hydrogen bonding forces
van der waals forces
a general term that includes both dipole-dipole forces and London forces.
- no dipole-dipole force in nonpolar molecules
- but there is still a force of attraction
- Fritz London explained this relationship and is now call the London forces
polar molecules exhibit
dipole-dipole forces that result in alignment of the molecules
London (dispersion) forces (LDF) in a non polar molecule
the charge is uniformly distributed over time. But in any one instant, the charge is not uniformly distributed. In that instant, there is an instantaneous dipole. To see how this works, let’s look at a neon atom
The instantaneous dipole of the neon atom induces an
instantaneous dipole in adjacent atoms, resulting in an attractive force between them.