||I U P A C
Organizations & People
list of quantities, units and symbols in physical chemistry
Several physical quantites have more than one
entry in the symbol column for different reasons:
- Both symbols are in use (e.g. p, P
for pressure and q, Q for heat);
- Different symbols are used for the same physical
quantity in different physical systems (for example, electron spin
quantum number s for a single electron and S for the
sum over several electrons);
- Alternative symbols are recommended to avoid
conflict in the notation for quantities which otherwise would have
the same symbols (e.g. Ea, to distinguish the energy
of activation from another energy E in the same context. The
unit 1 in the SI unit symbol column signifies a dimensionless quantity.
An extensive physical quantity, that is a quantity
proportional to the mass of amount of substance of a system, is often
symbolized by a capital letter. The corresponding specific quantity
(quantity divided by mass) may be represented by the corresponding lowercase
letter (example: volume V, specific volume v=V/m). A subscript
m to the symbol of an extensive quantityt denotes a molar quantity
(quantity divided by amount of substance), example: molar volume Vm=V/n.
It is permissible to omit the subscript m for molar when the text makes
it obvious that a molar quantity is intended.
Vectors are printed in bold-faced italic type. They can alternatively
be indicated by an arrow above the symbol.
Page last modified 29 May 2000.
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