A block of copper (SL model) is subjected to a change of state. The process is isentropic (that is, entropy does not change. Which of the following statements best describe the change of state. C. u is constant E. h is constant A. No change at all B. T is constant D. B and C

Respuesta :

To develop this problem it is necessary to apply the definitions of entropy change within the bodies

The change of entropy in copper would be defined as

[tex]\Delta S= \frac{\delta Q}{T}[/tex]

Where,

Q= Heat exchange

T = Temperature

For an incompressible substance, the change in the heat exchange is defined as

[tex]\Delta Q =mcdT[/tex]

Where,

m = Mass

c = Specific heat

Replacing in our equation we have that

[tex]\Delta S = \frac{mcdT}{T}[/tex]

[tex]\Delta S = mc ln \frac{T_f}{T_i}[/tex]

Since  [tex]\Delta S = 0[/tex], then

[tex]mcln\frac{T_f}{T_i} = 0[/tex]

[tex]T_f = T_i[/tex]

In this way for the change of enthalpy and internal energy you have to

[tex]\Delta U = \Delta h = mc\Delta T = mc(T_f-T_i)[/tex]

As [tex]Tf_= T_i[/tex], then

[tex]\Delta U = 0, \Delta H = 0[/tex]

Therefore the correct option is A. No change at All