Gibbs phase rule at critical point

[casas1010]

What is the degrees of freedom at the critical point of a 1 component system such as water. in my test I put zero because the critical point is a POINT that is fixed per substance.
is there any books that can back me up?
I heard that my teacher said there was 1 degree of freedom which I am pretty sure its wrong

 

[casas1010]

and if I am wrong what is your reasoning, thanks

 

[Chestermiller]

What is the degrees of freedom at the critical point of a 1 component system such as water. in my test I put zero because the critical point is a POINT that is fixed per substance.
is there any books that can back me up?
I heard that my teacher said there was 1 degree of freedom which I am pretty sure its wrong

I agree with you. P + V = C +2
C = 1
P = 3
so
V = 0

Chet