Question

A change of state, also known as a change of phase, is when a substance changes from one state of matter to another, such as changing from a liquid to a gas. A phase change is always associated with a change of heat, where the heat is either going into the substance or leaving the substance. Types of phase changes are melting, freezing, vaporization, condensation, and sublimation.

Answer 1

A phase change the way it is described sounds like a physical change only it can however be a chemical change in general, but with some exemptions. In the case of water turning into ice is not a chemical change, no chemical reaction is involved, nor its chemical composition altered only the arrangement of molecules changed.

In a phase change process there are many controlling factors so the dependence on concentration is not important but the dependence on othere factors are such that they cannot be cataegorised as as per the standard rules of pure chemical kinetics.

For example rate of evaporation of water can be calculated as follows

Rate of evaporation is proportional to the difference between the saturation vapour pressure (SVP) at the water temperature $clip_image002$ and the actual vapour pressure in the air ( $clip_image004$ )

$clip_image006$

As you can see in the equation there is no concentration term just so you cannot say this is a zero order reaction. But the equation does have a zero order format.

Hope this answers your question