Heat capacity vs specific heat

[September24]

What is the difference between the two

Is specific heat basically heat capacity for 1 gram of a substance? As in specific heat doesn't change, but heat capacity changes depending on amount of a substance?

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[brood910]

specific heat = q/mT
Heat capacity = q/T

So, mass x specific heat = heat capacity

 

[September24]

Makes sense! Thank you. I have another question but don't want to waste another topic.

On EK chemistry 590, it says


"If no heat is added to gas, it will cool as it expands"

I thought from PV=nRT, if volume increases, temperature increases?

How do I know if temperature increases or decreases if gas expands?

 

[brood910]

Expansion means work is done by the system.
In other words, change in volume is + and thus, work = -PV = negative.
When work is negative, heat leaks out of the system.
So, you are supposed to know that heat is lost when work is done by the system.

 

[September24]

That's pretty much the explanation I came up with. However, it doesn't coincide with PV=nRT. If a question were to ask

"What happens to temperature when a gas expands"....Would it increase (due to PV=NRT) or decrease (since energy/heat is expended to do PV work)

 

[brood910]

That's pretty much the explanation I came up with. However, it doesn't coincide with PV=nRT. If a question were to ask

"What happens to temperature when a gas expands"....Would it increase (due to PV=NRT) or decrease (since energy/heat is expended to do PV work)

You dont know if P is constant or not.
T wont change if the increase in V is offset by decrease in P.

 

[September24]

Oh okay. So it depends on what factors are held constant. Understood. Thank you