Phase change, isotherm and isotherm migration method are very important terms to learn in thermodynamics. This article is aimed at presenting the definition and mathematical discussion of some important thermodynamic terms such as phase change, isotherm and isotherm migration method etc. It offers an overview of some theoretical literature on these topics and presents their interpretation. Phase-change, Isotherm, Stefan Problems, and Isotherm Migration method are described with graphical or mathematical representation to clarify the concepts so that one can get brief idea about them.

This study focuses on different types of discussion about the phase change, isotherm, and isotherm migration method. From this article one can get a brief idea about the phase change and isotherm migration method. The essay offers definitions of the terms ("phase change", "isotherm"), explains the Stefan problems and offers methods of solution.

**Contents**

**Introduction:**

**Phase-change:**

**Isotherm:**

**Stefan Problems:**

**Methods of Solution:**

**Melting Ice:**

**Isotherm Migration Equations:**

**Conclusion:**

**Acknowledgement:**

**References:**