material technology

1. P&O Technology II:
Materials
Course Instructor: Agorsor Pius-Michael Sedinam
Course Code : POT 138
Semester Two

2. What are Materials?

3. Materials are any substance from which an artefact or a product is fabricated
or manufactured from.
For example, wood is the material that furniture(artefact or product) is
manufactured from

4. Activity
• Mention a product and suggest two materials that it was fabricated from

5. Properties of Materials
• Materials possess physical properties, mechanical properties as well as
chemical properties

6. Physical Properties of Materials
Melting point
• The melting point of a particular material, usually a solid is the temperature
at which the said material will melt.
Electrical conductivity
• The ability of a particular material to conduct electricity or allow the flow of
electric current through it.
Density
• Density is the mass per unit volume of a material

7. Mechanical Properties of Materials
• Hardness: ability to withstand surface indentation and scratching.
• Toughness: ability of a material to absorb energy(shock) and plastically deform
without fracturing.
• Resilience: ability of a material to absorb energy when it is deformed elastically.
• Ductility : ability to be drawn into wire
• Brittleness: inability to show indication before fracture

8. Chemical Properties
Chemical properties of materials such as reactivity are greatly determined by
the types of bonds formed between the atoms of the elements that forms the
material.
These bonds will be discussed in detail subsequently.

9. Classification of Materials
Materials may be classified according to:
• Physical Structure – solids, liquids and gases
• Chemical Structure – type of bonds

10. Activity
• What are the properties of solids, liquids and gases?

11. Teaser
• Why do you think it is necessary to take this course?

12. Types of Chemical Bonds
For the purpose of this course we’ll be focusing on :
• Ionic Bonds
• Covalent Bonds
• Metallic Bonds

13. Ionic Bonds
• Ionic bonds: involves transfer of electron from one atom to another.
• Properties
• High melting and boiling points.
• Conduct when in liquid state
• They form crystals
• They are hard

14. Covalent Bonds
• Covalent bonds: involves sharing of electron pairs
• Properties:
• Relatively low melting and boiling points
• Relative low bond energy
• More flammable
• Don’t conduct electricity even when dissolved in water

15. Metallic Bonds
• Metallic bonds: involves sharing of delocalized electrons among a lattice charged
cation.
• Properties
• Electrical conductivity
• Thermal conductivity
• Ductility
• Malleability
• High melting and boiling point
• Lustre

16. Activity
• List 5 materials that are used in P&O Practice in Ghana

17. Reading Assignment
• Find out what properties of Plaster of Paris(POP) make it suitable for use in
P&O.