you place a pure material in a piston and cylinder arrangement. The piston and c

Question

you place a pure material in a piston and cylinder arrangement. The

piston and cylinder operates in such a way that the pressure of the

material inside it is always constant. If you add heat, will the

temperature always go up?
A.No. It depends on whether the sign on Q is positive or negative.
B.No. There could be some material with a negative heat capacity.
C.Yes. The proportionality constant between heat and temperature change is Cp, the constant pressure heat capacity.
D.No,

there are several situations where the temperature does not increase

despite Q entering the system. For example, if the material is changing

phase at constant P, then the temperature will stay constant even though

heat is being added.

===============

I calculated the internal energy of liquid water at 100 C, and got 5.6 kJ/mol, which equals 311 kJ/kg.

The steam table in the back of Cengel and Boles says that the internal energy of liquid water at 100 C and 1 atm is 419 kJ/kg.

Why is my answer so different from the one in the book?
A.I don't know... but I find it disturbing.
B.You used a reference point of 25 C, and the steam table uses a reference point of 0 C.
C.You used Cp instead of Cv.
D.You made an arithmetic error.

=====================

For a pure species at constant pressure, boiling point temperature is equal to the saturation temperature.
True
False

===============

As temperature increases, the saturation pressure goes down.
True
False

================

Suppose

Explanation / Answer

1. true bcoz tht is the temperture at which a substance will under a change in its state

2. false . this is evident from ideal gas equation, PV = nRT   , P is directly proportional to T

3.D.No,there are several situations where the temperature does not increase

despite Q entering the system. For example, if the material is changing

phase at constant P, then the temperature will stay constant even though

heat is being added.

4. B.You used a reference point of 25 C, and the steam table uses a reference point of 0 C.

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