specific heat گرمای ِ آبیزه garmâ-ye âbizé Fr.: chaleur spécifique The quantity of heat required to raise the temperature of 1 gm of
a substance through 1 °C. More generally, the → heat capacity
of a unit mass of a substance. For a homogeneous body it is expressed as:
C = dQ/M dT, where dQ is the quantity of heat transferred to a
mass of M to raise the temperature by dT. It is often convenient
to use the gram-mole as a unit of mass, → molar heat capacity.
For a gas there are two principal specific heats depending on the way in
which the temperature is increased: i) that measured at constant pressure,
CP, and ii)
that measured at constant volume, CV. The specific heat
CP is greater than CV, because a gas heated at
constant pressure expands, and heat energy must be supplied equivalent to the work
done in the expansion. The ratio γ = CP/CV is called
the → adiabatic index. It varies from 1.66 for mono-atomic gases
to a little over 1 for gases with complex molecules.
See also: → specific; → heat. |
