∆‡Cp = (∂∆‡H/∂T)p= T(∂∆‡S/∂T)pIf the rate constant is expressible in the form ln k = a/T
- b + c ln T + dT, then
∆‡Cp= (c–1) R + 2dRTheat of atomization The amount of energy required
to dissociate 1 mole of a given substance into atoms.
heat of condensation Heat released when vapors
change state to liquid. It is the amount of heat that
must be removed from 1 gram of a vapor (specific heat
of condensation) at its condensation point to condense
the vapor with no temperature change. The molar heat
of condensation refers to the quantity of heat released
by a mole of vapor.
heat of crystallization The amount of heat that must
be removed when 1 mole of a given substance crystal-
lizes from a saturated solution of the same substance.
heat of fusion The amount of heat required to melt
1 gram of solid at its melting point with no change in
temperature.
heat of reaction The amount of heat absorbed from
the complete chemical reaction of molar amounts of
the reactants.
heat of solution The amount of energy required or
released when 1 mole of solute dissolves in a solvent.
The value is positive if heat is absorbed (endothermic)
and negative if heat is released (exothermic).
heat of sublimation The amount of energy required
to convert 1 mole of a substance from the solid to the
gas state (sublimation) without the appearance of the
liquid state.
heat of vaporization The heat energy required to
convert 1 gram of liquid to vapor without a change in
temperature of the substance being vaporized.
heat-shock proteins(HSPs) A family of closely
related proteins, widely distributed in virtually all organ-
isms from plants, animals, microorganisms, and
humans. Even though they are found in widely different
sources, they show structural similarity. HSP expression
increases in response to physiological stresses such as
rise in temperature, pH changes, and oxygen depriva-
tion. Many of these stresses can disrupt the three-dimen-
sional structure, or folding, of a cell’s proteins, and HSPs
bind to those damaged proteins, helping them refold
back into their proper shapes. They also help newly syn-
thesized polypeptides fold and prevent premature inter-
actions with other proteins. HSPs, also called
chaperones, aid in the transport of proteins throughout
the cell’s various compartments and aid in the destruc-
tion of peptides specific to tumors or pathogens.heavy water Water in which hydrogen atoms are
replaced by deuterium, a heavy isotope of hydrogen.Heisenberg uncertainty principle It states that it is
not possible to determine accurately both the momen-
tum and position of an electron simultaneously.helium An inert gas. An ELEMENTwith atomic num-
ber 2. Helium is produced in stars and is the second
most abundant element in the universe. Its atom con-
tains two protons, two neutrons, and two electrons,
although there is another stable but very rare isotope
with only 1 neutron.helix A particular rigid left- or right-handed arrange-
ment of a polymeric chain, characterized by the num-
ber of strands, the number (n) of units per turn, and its
pitch (p), which is the distance the helix rises along its
axis per full turn. Examples of single-stranded helices
are the protein helices: α-helix: n = 3.6, p = 540 pm;(^3) 10-helix: n = 3.0, p = 600 pm; π-helix: n = 4.4, p =
520 pm.
See alsoDOUBLE HELIX.
heme A near-planar COORDINATION complex ob-
tained from iron and the dianionic form of PORPHYRIN.
heme 125