Word
Definition
Amorphous solid
amorphous solid.
A solid that does not have a repeating, regular three-dimensional arrangement of atoms, molecules, or ions.
Boiling
Boiling, a type of phase transition, is the rapid vaporization of a liquid, which typically occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmospheric pressure. Thus, a liquid may also boil when the pressure of the surrounding atmosphere is sufficiently reduced, such as the use of a vacuum pump or at high altitudes. Boiling occurs in three characteristic stages, which are nucleate, transition and film boiling. These stages generally take place from low to high surface temperatures, respectively.
Boiling point
(bp) standard boiling point; normal boiling point.
The temperature at which the vapor pressure of a liquid is equal to the external pressure on the liquid. The standard boiling point is the temperature at which the vapor pressure of a liquid equals standard pressure.
Calorimeter
An insulated vessel for measuring the amount of heat absorbed or released by a chemical or physical change.
Celsius
(°C) Celsius temperature scale; Celsius scale.
A common but non-SI unit of temperature, defined by assigning temperatures of 0°C and 100°C to the freezing and boiling points of water, respectively.
Compressibility
Condensation
condensed.
1. The conversion of a gas into a liquid is called condensation. Condensation usually occurs when a gas is cooled below its boiling point. 2. A reaction that involves linking of two molecules with the elimination of water (or another small molecule).
Condense
condensation
Critical point
critical state.
State at which two phases of a substance first become indistinguishable. For example, at pressures higher than 217.6 atm andtemperatures above 374°C, the meniscus between steam and liquid water will vanish; the two phases become indistinguishable and are referred to as a supercritical fluid.
Critical pressure
(Pc)
The pressure at the critical point.
Critical temperature
(Tc)
The temperature at the critical point. A gas above the critical temperature will never condense into a liquid, no matter how much pressure is applied. Most substances have a critical temperature that is about 1.5 to 1.7 times the standard boiling point, in kelvin.
Crystal structure
Crystalline solids
crystalline.
A solid that has a repeating, regular three-dimensional arrangement of atoms, molecules, or ions.
Deposition
Diffusion
diffuse.
The mixing of two substances caused by random molecular motions. Gases diffuse very quickly; liquids diffuse much more slowly, and solids diffuse at very slow (but often measurable) rates. Molecular collisions make diffusion slower in liquids and solids.
Effusion
effuse.
Gas molecules in a container escape from tiny pinholes into a vacuum with the same average velocity they have inside the container. They also move in straight-line trajectories through the pinhole.
Elastic collision
Endothermic
endothermic reaction; endothermic process. .
A process that absorbs heat. The enthalpy change for an endothermic process has a positive sign.
Enthalpy change
(H) enthalpy change.
Enthalpy (H) is
defined so that changes in enthalpy (
H)
are equal to the heat absorbed or released by a process running at
constant pressure. While changes in enthalpy can be measured using
calorimetry, absolute values of enthalpy usually cannot be determined.
Enthalpy is formally defined as H = U + PV, where U is the internal
energy, P is the pressure, and V is the volume.
Enthalpy of combustion
(Hc)
heat of combustion.
The change in
enthalpy
when one mole of compound is completely combusted. All carbon in the
compound is converted to CO2(g), all hydrogen to H2O(
),
all sulfur to SO2(g), and all nitrogen to N2(g).
Enthalpy of reaction
(Hrxn)
heat of reaction.
The heat absorbed or released by a chemical reaction running at constant pressure.
Equilibrium vapor pressure
Evaporate
To convert a liquid into a gas.
Evaporation
vaporization.
Conversion of a liquid into a gas.
Exothermic
exothermic reaction; exothermic process.
A process that releases heat. The enthalpy change for an exothermic process is negative. Examples of exothermic processes are combustion reactions and neutralization reactions
Expansion
Freeze
Freezing
Freezing point
(mp) standard melting point; normal melting point; melting point.
The temperature at which the vapor pressure of a liquid is equal to the vapor pressure of the corresponding solid form. The liquid and solid forms can coexist at equilibrium at the freezing point. The standard melting point is the melting point at standard pressure.
Graph: T vs phase of H2O
Heat
Heat is a transfer of energy that occurs when objects with different temperatures are placed into contact. Heat is a process, not a property of a material.
Hess’s law
law of constant heat summation; Hess's law of heat summation.
The heat released or
absorbed by a process is the same no matter how many steps the process
takes. For example, given a reaction A 
B,
Hess's law says that H
for the reaction is the same whether the reaction is written as A C B
or as A B.
This is the same as writing that H(A B)
= H(A C)
+ H(C B).
Joule
(J)
The SI unit of energy, equal to the work required to move a 1 kg mass against an opposing force of 1 newton. 1 J = 1 kg m2 s-2 = 4.184 calories.
Kelvin
(K)
The SI base unit of temperature, defined by assigning 273.16 K to the temperature at which steam, ice, and water are at equilibrium (called the triple point of water). The freezing point of water is 273.15 K.
Kinetic energy
The energy an object possesses by virtue of its motion. An object of mass m moving at velocity v has a kinetic energy of ½mv2.
Kinetic molecular theory
Melting
Melting point
Normal boiling point
See Boiling point
Phase
in phase; out of phase; wave phase.
1.A
phase is a part of a sample of matter that is in contact with other
parts but is separate from them. Properties within a phase are
homogeneous (uniform). For example, oil and vinegar salad dressing
contains two phases: an oil-rich liquid, and a vinegar-rich liquid.
Shaking the bottle breaks the phases up into tiny droplets, but there
are still two distinct phases. 2. In wave motion, phase is the
fraction of a complete cycle that has passed a fixed point since the
current cycle began. The phase is often expressed as an angle, since a
full cycle is 360^deg; (2 
).
Two waves are "in phase" if the peaks of one wave align with the peaks
of the other; they are "out of phase" if the peaks of one wave align
with the troughs of the other.
Phase diagram
phase map.
A map that shows which phases of a sample are most stable for a given set of conditions. Phases are depicted as regions on the map; the borderlines between regions correspond to conditions where the phases can coexist in equilibrium.
Sublimation
sublimate; sublimating.
Conversion of a solid directly into a gas, without first melting into a liquid.
Temperature
Temperature is an intensive property associated with the hotness or coldness of an object. It determines the direction of spontaneous heat flow (always from hot to cold).
Thermochemical equation
An compact equation
representing a chemical reaction that describes both the stoichiometry
and the energetics of the reaction. For example, the thermochemical
equation CH4(g) + 2 O2(g) CO2(g)
+ 2 H2O(g), H
= -2220 kJ means "When one mole of gaseous CH4 is burned in
two moles of oxygen gas, one mole of CO2 gas and 2 moles of
steam are produced, and 2220 kilojoules of heat are released."
Thermochemistry
The study of heat absorbed or released during chemical changes.
Transition states
In a chemical reaction, the reagents have to join together into a great big blob before they can fall back apart into the products. This great big blob is called the activated complex
Triple point
The temperature and pressure at which the solid, liquid, and gaseous forms of a substance are at equilibrium.
Vapor Pressure
vapour pressure.
The partial pressure of a gas in equilibrium with a condensed form (solid or liquid) of the same substance.
Vaporization
See evaporate
Volatile liquids
volatility.
A solid or liquid material that easily vaporizes. A material with a significant vapor pressure.