GENCHEM - MIDTERM

phase

is defined as a homogeneous state in which the substance has a uniform composition and governed by the same intermolecular forces throughout the material

sublimation

solid to gas

melting

solid to liquid

boiling or evaporation

liquid to gas

freezing

liquid to solid

condensation

gas to liquid

deposition

gas to solid

phase changes

are accompanied by a change that occurs as a result of energy interactions and the intermolecular forces in the substance itself

endothermic

when molecular oder decreases, this results in absorption of energy

exothermic

when molecular order increases, this results in release of energy

enthalpy

the amount of heat energy transferred from the surroundings to the substance is a change in

specific heat

the amount of heat needed to raise the temperature of a specific substance by one degree celsius is

melting point

the temperature at which a substance melt

enthalpy of fusion

the amount of heat needed to melt a substance

boiling point

the temperature at which liquid turns to gas is called

enthalpy of vaporization

the amount of heat needed to complete the evaporation process

phase triangle

summarizes the associated enthalpy change for phase transformations at a specific temperature and pressure

dynamic equilibrium

is when the rates of opposing simultaneous phase changes are equal at specific temperature and pressure

liquid-vapor equilibrium

is achieved when the rate of condensation becomes equal to the rate of evaporation

vapor pressure

is the pressure exerted by the vapor molecules in this dynamic equilibrium

normal boiling point

is the temperature at which the vapor pressure of a substance is equal to atmospheric pressure

molar heat of vaporization

is the energy required to vaporize one mole of a liquid

critical point

is the temperature and pressure at which the distinction between liquid and vapor phases disappears

solid-liquid equilibrium

occurs when the rate of melting equals the rate of freezing

molar heat of fusion

is the energy required to melt one mole of a solid

solid-gas equilibrium

occurs when the rate of sublimation equals the rate of deposition

sublimation

is the direct transformation from solid to gas

molar heat of sublimation

is the energy required ti sublime one mole of a solid

phase diagram

shows the phase of a substance as pressure (y-axis) is plotted against temperature (x-axis)

triple point

the point where the three curves intersect

heating and cooling curves

are used to track heat changed associated sith complex phase transformations

total heat

is the sum of all heat absorbed in each segment

phases

data points

curves/lines

triple point

general features of phase diagrams