What determines the phase of a substance? temperture, humidity, amount of the substance or pressure

Temperature and pressure.

Explanation:

The phase of any substance is depend on the temperature as well as pressure. Because if the substance is change from its solid state to liquid means melting occur, we are going to increase its temperature at a particular pressure affect.

And humidity also change the pressure but we here consider the pressure so we can neglect the humidity.

The phase does not depend on the amount of substance the rate of change of phase is not change with respect to amount of substance.

Therefore, the phase of change of substance is depends on temperature as well as on pressure.