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specific heat and heat capacity

specific heat and heat capacity

specific heat and heat capacity

(OP)
I remember posting my opinion in a thread (number forgotten) on the Mechanical Engineers forum discussing the difference between these two expressions, w/o seeing a feedback. My view is that although interconnected, these expressions have different meanings, as follows:

The heat capacity of an object or a system, is the proportionality factor C between the heat transferred ΔQ, and the resulting change in temperature ΔT. It expresses the quantity of heat to raise a system one degree in temperature in a specified way, usually at constant volume or constant pressure. Aka thermal capacity.
 
ΔQ = CΔT

Thus it depends on the object's mass and on the substance it is made from, and using SI units it would be measured in J/K.

Different substances are characterized in terms of specific heat c, or heat capacity per unit mass. The heat capacity of an object is then the product of its mass m, and specific heat.

ΔQ = mcΔT

The specific heat c, measured in J/(kg.K) would then be the quantity of heat to raise the unit mass of an object one degree in temperature (assuming no physical or chemical change occurs).

In the same context Molar heat capacities would be measured in J/(mol.K).

I'd appreciate reading critical comments, especially those referring to dimensionless specific heats (when comparing with a reference material, usually water).

RE: specific heat and heat capacity

Sounds right to me.  The "specific" usually means "per unit mass", usually in terms of energy capacity.  Handy becuase it takes mass out of an equation when it would cancel out anyway.

i.e. specific kinetic energy = 0.5v2
specific potential energy (due to height) = gh

I have not seen molar heat capacities used anywhere.

RE: specific heat and heat capacity

(OP)

To MintJulep and TheTick, thanks for your answers.
Molar heat capacities would be, in fact, Cp in J/(mol.K). See table p. 12-171 on the CRC Handbook 77th Ed., for selected solids.

RE: specific heat and heat capacity

That is absolutely right. Application of heat capacity, directly,as far as I know, is used in the derivation of LMTD for HXs, otherwise it is specific heat.

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