In this unit we will discuss about temperature and heat which are a fundamental aspects of many physical situations. Temperature and heat are very different concepts and in this unit we make a clear distinction between them. We will also learn how to measure heat energy and the factors on which heat energy for a given body depends. We will then learn the difference between specific heat capacity and heat capacity. We will also discuss the mechanisms by which heat can be transferred from one body to another (or from one region to another). Finally we will discuss how heat is used in calorimetery, and how it is involved in changes of states of matter.