When you boil an egg what undergoes a chemical change?

A chemical change is a change that cannot be reversed, usually chemically combining the elements together (hence the name). The composition of the element also changes. 

When boiling the egg, the yolk and the liquid inside both undergo a chemical change. You will notice that the yolk and liquid cannot be liquified again. 

Hope I helped :) 

You need to divided twenty four by a dozen them by the temperature it is getting cook by

Yes it would be a physical change.