What is the Difference Between Latent Heat and Specific Heat?

[Jbreezy]

Homework Statement

I took a test and got it back I'm wondering if my prof. definition is correct.
The heat required per unit mass of a substance to produce a phase change is called?

A. specific heat B. Specific heat capacity C. latent heat

I said it was C.
He say's B
Please explain. Thanks

 

[cepheid]

From the terminology I'm familiar with, specific heat capacity (B) is the amount of heat required per unit mass of a substance to cause a unit of temperature change. I have heard the term "latent heat" (C) used to describe the heat required to produce a phase change e.g. latent heat of fusion, latent heat of vaporization.

 

[Jbreezy]

Thanks, I looked up definitions I feel something is wrong here. Anyone else know? Thanks for the reply.

 

[cepheid]

Just for clarification, I'm saying that I thought the answer should be C as well, because latent heat is what pertains to phase changes, whereas specfic heat capacity is just for temperature changes of the substance at a given phase, not during a phase transition. This is AFAIK.

 

[technician]

Latent heat is as stated...the energy needed to produce a phase change (usually solid-liquid, liquid-vapour)
If it expressed as 'per unit mass' then it should be called SPECIFIC latent heat. This might be the source of confusion because one of your options is specific heat capacity.
LATENT means 'hidden' because the heat energy does not cause a change in temperature.
SPECIFIC means per unit mass (usually per kg)

 

[Jbreezy]

What is AFAIK?
I think I might challenge him on his grading of this question. I need to be sure though. Thanks for reply;s
I feel this question is ambiguous.

 

[cepheid]

What is AFAIK?
I think I might challenge him on his grading of this question. I need to be sure though. Thanks for reply;s
I feel this question is ambiguous.

It means As Far As I Know.

Use whatever terminology is in your textbook and notes. That having been said, given my answer, and technician's, it seems pretty clear that it's a bad question. You can have specific latent heat or latent heat, and these have to do with phase transitions. Heat capacity and specific heat capacity do not.

 

[CWatters]

Your professor is wrong. The answer is C.

See wikipedia..

A & B). Specific Heat Capacity & Specific Heat

http://en.wikipedia.org/wiki/Heat_capacity#Extensive_and_intensive_quantities

Heat capacity (usually denoted by a capital C, often with subscripts), or thermal capacity, is the measurable physical quantity that shows the amount of heat required to change the temperature of an object or body by a given amount.

Derived quantities that specify heat capacity as an intensive property, i.e., independent of the size of the body or amount of a sample, are the molar heat capacity, which is the heat capacity per mole of a pure substance, and the specific heat capacity, often simply called specific heat, which is the heat capacity per unit mass of a material. .

C). Latent Heat
http://en.wikipedia.org/wiki/Latent_heat

Latent heat is the heat released or absorbed by a body or a thermodynamic system during a constant-temperature process. A typical example is a change of state of matter, meaning a phase transition such as the melting of ice or the boiling of water.

snip

A specific latent heat (L) expresses the amount of energy in the form of heat (Q) required to completely effect a phase change of a unit of mass (m), usually 1kg, of a substance as an intensive property:

In all cases the word "specific" generally means it's "per unit mass" of the material.

 

[CWatters]

EDIT: Now that I look again at the options I believe most people would answer c) Latent Heat however if I was being picky I would prefer d) Specific Latent Heat because the question says "per unit mass".

Either way it's not Specific Heat or Specific Heat Capacity.

 

[Jbreezy]

Hey thanks for the help I will let you guy's know the outcome. Appreciated.

 

[Jbreezy]

I got my 2 points back thanks for the reply's.