Chapter 11 - Liquids and Intermolecular Forces Flashcards
What are the three types of van der Waals forces?
Dispersion forces, dipole-dipole attractions, and hydrogen bonding.
What are condensed phases?
Solids and liquids.
What is a dispersion force?
The motions of electrons in one atom influence the motions of electrons in its neighbors. This brief interaction is significant only when molecules are very close together.
What is polarizability?
It is the ease with which the charge distribution (electron cloud) is distorted. More polarizable molecules have larger dispersion forces.
What are dipole-dipole forces?
These forces originate from electrostatic attractions between a partially positive end of one molecule and the partially negative end of a molecule. It is effective only when molecules are very close together.
What is a hydrogen bond?
It is an attraction between a hydrogen atom attached to a highly electronegative atom (usually F, O, or N) and a nearby small electronegative atom and another molecule or chemical group.
What is an ion-dipole force?
It is a force that exists between an ion and a polar molecule.
What is viscosity?
It is the resistance of a liquid to flow. The more it has, the more slowly it flows.
What is surface tension?
It is the energy required to increase the surface area of a liquid by a unit amount.
What are cohesive forces?
It is an intermolecular force that binds similar molecules to one another, such as hydrogen bonding in water.
What is an adhesive force?
It is an intermolecular force that binds a substance to a surface.
What is capillary action?
It is the ability of a liquid to flow in narrow spaces without the assistance of, and opposition to, external forces like gravity.
What is a phase change?
It is simply a change of state, such as gas to liquid or liquid to solid.
What is fusion?
It is the process of melting, from solid to liquid.
What is vaporization?
It is the phase change from liquid to gas.
What is condensation?
It is the phase change from gas to liquid.
What is freezing?
It is the phase change from liquid to solid.
What is sublimation?
It is the phase change from solid to gas.
What is deposition?
It is the phase change from gas to solid.
What is critical temperature?
It is the highest temperature at which a distinct liquid phase can form.
What is critical pressure?
It is the pressure required to bring about liquefication at this critical temperature.
What is a supercritical fluid?
It is when the temperature exceeds the critical temperature and the pressure exceeds the critical pressure, and the liquid and gas phases are indistinguishable from one another. It expands to fill its container like a gas, but the molecules are still tightly spaced like a liquid.
What is vapor pressure?
It is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system.
What is dynamic equilibrium?
The condition in which two opposing processes occur simultaneously at equal rates.
What does it mean when a liquid is volatile?
It means it will evaporate readily.
What is a boiling point of a liquid?
It is the temperature at which its vapor pressure equals the external pressure, acting on the liquid surface.
What is the normal boiling point of a liquid?
It is the boiling point of a liquid at 1 ATM.
What is a phase diagram?
It is a graphic way to summarize the conditions under which equilibria exist between the different states of matter.
What is a normal melting point?
The melting point at 1 ATM of a substance.
What is a triple point?
The point at which all 3 phases (solid, liquid, and gas) are in equilibrium.
What is a liquid crystal?
It is the viscous, milky state that some substances exhibit between the liquid and solid states.
What is a nematic liquid crystal?
It is a crystal liquid in which the molecules are aligned so that their long axes tend to point in the same direction but the ends are not aligned with one another.
What are smectic A and smectic C liquid crystals?
They are liquid crystals in which the molecules maintain the long-axis alignment seen in nematic crystals, but in addition they pack into layers.
What is a cholestoric liquid crystal?
It is a liquid crystal in which the molecules are arranged in layers, with their long axes parallel to the other molecules within the same layer.
Asymmetric molecular geometries are affected by what kind of Van der waals force (primarily)?
Dipole-dipole forces, which affect polar (asymmetric) bonds.
Symmetric molecular geometries are affected only by what kind of Van der Waals force?
London dispersion forces
