GAS | LIQUID | SOLID |
---|---|---|
Assumes both volume and shape of its container | Assumes shape of portion of container it occupies | Retains own shape and volume |
Expands to fill its container | Does not expand to fill its container | Does not expand to fill its container |
Is compressible | Is virtually incompressible | Is virtually incompressible |
Flows readily | Flows readily | Does not flow |
Diffusion within a gas occurs rapidly | Diffusion within a liquid occurs slowly | Diffusion within a solid occurs extremely slowly |
There are three types of intermolecular attractions that exist between electrically neutral molecules:
The first two are collectively called van der Waals forces after Johannes van der Waals (1837–1923), who developed the equation for predicting the deviation of gases from ideal behavior.
Dispersion Forces
The Dispersion force
(also called London dispersion forces or induced dipole–induced dipole interactions).
The instantaneous dipole on one atom can induce an instantaneous dipole on an adjacent atom, causing the atoms to be attracted to each other.
It is significant only when molecules are very close together.
The ease with which the charge distribution is distorted is called the molecule’s polarizability.
Polarizability increases as the number of electrons in an atom or molecule increases.
[ ] Linear molecule—Larger surface area enhances intermolecular contact and increases dispersion force.
[ ] Spherical molecule—Smaller surface area diminishes intermolecular contact and decreases dispersion force.
Dipole–Dipole Interactions
Hydrogen Bonding
Ion–Dipole Forces
Comparing Intermolecular Forces
Viscosity
Surface tension
Capillary Action
The rise of liquids up very narrow tubes.
Phase Changes when matter changes from one state (solid, liquid, gas, plasma) to another.
Energy Changes Accompany Phase Changes
Vapor pressure
Heat of vaporization
Or the enthalpy of vaporization.
The energy required to cause the transition of a given quantity of the liquid to the vapor.
\n Heat of sublimation
The particles of a solid can move directly into the gaseous state. The enthalpy change required for this transition.
Heating curve
Critical temperature
Critical pressure
is the pressure required to bring about liquefaction at this critical temperature.
Supercritical fluid
Vapor pressure
Dynamic equilibrium
Volatile
Boiling point
Normal boiling point
The boiling point of a liquid at 1 atm (760 torr) pressure.
A phase diagram is a graphic way to summarize the conditions under which equilibria exist between the different states of matter.
The phase diagram for any substance that can exist in all three phases of matter.
Generic phase diagram for a pure substance. The green line is the sublimation curve, the blue line is the melting curve, and the red line is the vapor-pressure curve.
The red curve is the vapor-pressure curve of the liquid, representing equilibrium between the liquid and gas phases.
The green curve, the sublimation curve, separates the solid phase from the gas phase and represents the change in the vapor pressure of the solid as it sublimes at different temperatures.
The blue curve, the melting curve, separates the solid phase from the liquid phase and represents the change in melting point of the solid with increasing pressure.
Point T, where the three curves intersect, is the triple point, and here all three phases are in equilibrium.
[ ] In 1888 Friedrich Reinitzer, an Austrian botanist, discovered that the organic compound cholesteryl benzoate has an interesting and unusual property.
Liquid Crystal
Types of Liquid Crystals
Liquid phase
Nematic liquid crystalline phase
Smectic A liquid crystalline phase
Smectic C liquid crystalline phase
Cholesteric liquid crystalline phase