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Forty__ t1_jbjpi4w wrote

Specific heat capacity refers to the heat capacity per mass. As you can probably imagine, it is not always useful to talk about the total heat capacity, e.g., if you want to characterize not an object, but a type of material. There is also molar heat capacity, which is the heat capacity per 1 mol particles and which is directly connected to the specific heat capacity through the molar mass of a material.

For specific impulse, it is about momentum change (which is force) per ejected unit of mass. So that isn't necessarily comparable to specific heat capacity because it does not just depend on the material that is ejected but rather by the exit velocity of the ejected material. In this case, you might also consider the volume-specific impulse, which gives you the force per ejected unit of volume, as you have limited space in a rocket.

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bobgom t1_jbn2m3p wrote

Even though it may be technically wrong specific heat is often used to mean molar heat capacity even in many publications.

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Coomb t1_jbpcbll wrote

"Specific" was, at least originally, a generic term to indicate that the parameter being discussed has been normalized by some relevant unit to turn it from an extensive property to an intensive property. Occasionally in the context of specific heat, you will actually see people write out "mass specific heat" or "volumetric specific heat" or "molar specific heat".

People working in a particular context almost certainly just use the term specific heat to refer to whichever specific intensive property is most often relevant, so it doesn't surprise me to hear that some people use it to mean molar specific heat rather than mass specific heat.

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