We’ve already mentioned that the materials used in engineering must be ﬁ t for purpose and suitable for the application in which they are used. Crucial in all of this are the physical properties of the materials in question. In this chapter we will continue our study of materials by looking in more detail at their properties and the processes that can be applied to them in order to change them. We start by introducing the chemical, electrical and magnetic properties of materials and then move on to the essential physical properties of materials. This chapter also introduces you to a valuable source of reference information in the form of a database of materials and their properties. As you work through the chapter you will be able to add to the database and modify it for your own use.