LSC S2:MATERIALS

Introduction
MATERIALS If you take a look around your immediate environment, you will realise the wat most of the things that you see, whether it is an object, tool or machine are made of something. It could be a chair, table, your bag, pen, classroom walls, the floor, etc. All these were made from certain substances that
occupy space and have weight (matter).Therefore the matter from which something is made is called material.
You can use different materials to make a number of objects or construct different structures like houses and bridges to serve various purposes. In Uganda the most commonly used materials are timber, wood, metal, clay, plastic and glass.
The choice of material to be used to make a certain item depends on a number of factors as you will discover in this chapter. These include but are not limited to; suitability for the purpose, availability and cost. In this chapter, you will understand the nature of materials and design
materials correctly.

Types of Materials
There are many types of materials available but we shall focus on metal, wood, clay and plastic.
Metal: A metal is a solid material which is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity. Some examples are iron, copper, gold, silver, aluminium, and alloys such as steel,
bronze and brass.
Wood: Wood is a natural material got from trees. Plastic: Plastic is an artificial material made from petroleum products. Wood Metal

Clay: Clay is a natural material with little sand obtained from swamps or wetlands.
In the following activity, you will identify the types of materials used to make different products and items.
Identifying types of common materials used for making different products and items
What you need: Exercise books, pens and pencils, scriber, a ruler and pictures of different items/products
What to do: In pairs, carry out this activity.

1. Study your immediate environment and observe the different items and products. Identify the materials they are made of.
2. Suggest reasons why those materials were used to make the items and the products.
3. Record your findings in a table such as follows and present your work to your class and get feedback.

Properties of Materials
Different materials have different mechanical properties. Mechanical properties of materials are those properties which affect the mechanical strength
and ability ofa material to be moulded into a suitable shape. Some of the
typical mechanical properties of materials include:
hardness:
strength:
toughness:
the ability of a material to resist cutting, wear or abrasion (rubbing) ability of a material to withstand force without breaking, for example pulling, compression or weight ability of a material to withstand a force without breaking

There are many more properties of materials. Individually research about the other properties besides the ones listed above. Write your findings in your notebooks.

Exploring properties of materials
Activity 8.2
What you need: Plastic i.e. PVC materials, alkobond, wood, metal, and a computer where possible
What to do: In groups, carry out this activity.
Follow the instructions under procedure. Apply various tests to the materials to find out their properties. Fill these in the spaces provided in the following table:

You can also heat some materials to test for heat conductivity. Record your findings (work) in your books and exchange your books with other groups for comparison and to get feedback. Make corrections where
necessary.

There are many materials with different properties. You need a good method to display and select them. A useful method of doing this is by plotting them in a material property selector chart.
Activity 8.3
Selecting materials to use for designing according to their properties
What you need: Exercise books, pens and pencils, manila paper, ruler and a computer with an internet connection where possible
What to do: In groups, carry out this activity.

1. Explore the properties of wood, metal, plastic and clay. Write them down in your books.
2. Use the material property selector table or chart to tick the property which is suitable for each respective material. Draw it in your books.

Using a Material Property Selector Chart
Drawing a material property selector chart for making a chopping board

What you need: Exercise books, pens and pencils, ruler, and a computer
with an internet connection where possible
What to do: In groups, carry out this activity.
1.Make a property selector chart for choosing the correct material for making a chopping board of size
300x200x25 mm.
2.Draw a property selector chart for the case in your books.
3.Exchange your books with your colleagues and compare your charts. Is there any difference
between your property selector charts?
Figure 8.2: A chopping board