Materials in Today's World



The crystal structure of a material can directly affect their properties. For example, gold and silver which share a common crystal structure are much less brittle than the metals beryllium and magnesium which possess a different crystal structure. Also, crystalline and noncrystalline materials of the same composition can possess significantly differing properties. In this lesson, we will discuss how structure can affect materials properties and also introduce imperfections, which can have major impacts on the properties of materials.

Learning Objectives

By the end of this lesson, you should be able to:

  • List and explain the contributions to material processing made by the Egyptians.
  • Explain the difference between melting and smelting.
  • Distinguish between single crystals and polycrystalline materials.
  • Describe the difference in atomic/molecular structure between crystalline and non-crystalline materials.
  • Draw unit cells for face-centered cubic, body-centered cubic, and hexagonal close-packed crystal structures.
  • Define polymorphism and allotropy.
  • Sketch the three orthogonal crystal systems (cubic, tetragonal, orthorhombic) and the hexagonal crystal system with proper lattice parameter labels.
  • Define isotropy and anisotropy with respect to material properties.
  • List and describe the different types of imperfections in a crystal.

Lesson Roadmap

Lesson 5 will take us 1 week to complete. Please refer to Canvas for specific due dates.

Lesson Roadmap
To Read Pages 98 to 133 (Chapter 5 and 6) of Materials for Today's World, Custom Edition for Penn State University (custom e-book)
To Watch Metal: The Secret Life of Materials
To Do Lesson 5 Quiz


If you have general questions about the course content or structure, please post them to the General Questions and Discussion forum in Canvas. If your question is of a more personal nature, feel free to send a message to the instructor through Canvas email. I will check each of these daily to respond.