Thermo Chemistry: Explaining Cp vs Cv

[zorro]

This is a statement in my book 'The heat capacity at constant pressure Cp is generally larger than that at constant volume Cv because at constant pressure, a part of heat added to the substance may be used in work of expanding whereas at constant volume all the added heat produces a rise in temperature'. I did not understand these two things-

At constant pressure, how can heat added be used for expanding (since expanding leads to change in pressure).

At constant volume what if the added heat expands the gas?

 

[Borek]

If you heat something it usually inflates, to keep the pressure constant it has to expand.

In constant volume heated gas WANTS to expand - but as the volume is kept constant, it is impossible, so instead the pressure goes up.

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[zorro]

what is the difference between expansion and inflation of gas?

 

[Borek]

None as far as I am concerned, sorry if it sounded as there is a difference.