Why materials are processed

They are mostly supportive of sustainable living practices, and are becoming very trendy as a result. The introduction to this unit links it to the units that have preceded it. We call materials that have not yet been processed raw materials. Raw materials are made into other things. When raw materials are in the form in which they are found in nature, we can call them natural materials.

A natural material is any material that comes from plants, animals, or the ground. We have learnt that there are many different ways in which materials can be processed to give them new properties. After processing they may look, smell, feel or taste different. They will probably also be used for a totally different purpose from before. Processed materials are materials which have been refined or built by humans from raw materials.

Some examples include paper, steel and glass. Teacher's note: In this activity the learners must study a list of materials and then decide which represent raw materials and which represent processed materials.

It is recommended that this should be a small group activity, since discussion and joint decision making is required. All the materials in the list above have been placed into a table below. Discuss each material in your group and decide how to classify it. Is it a raw material or a processed material? Does it come from plants, animals or the ground? You can look at the table to guide you. Use your discretion in evaluating learners' answers; some possibilities have been suggested in the table.

Materials that have been processed are very useful to us because they have special properties. We already know that processed materials can be strong and durable. But what other properties do they have?

Let's look at some example. What do you put on when it is raining outside? Some processed materials are useful to use because they are waterproof. A rain jacket is made of a material which is waterproof, and so is an umbrella. Maybe you might wear gum boots or wellingtons?

These shoes are very waterproof and made from specially processed plastic and rubber. Paint is a processed material.

The pigments used to make paint are natural materials, but the final product is a processed material. Do you remember we mentioned pigments last term in Life and Living? What was the green pigment used in photosynthesis to make food for plants? Paint is in a liquid form so it can be easily painted on a surface. Paint also has colour so it can be used decoratively. We paint the walls in our houses, we paint the outside walls of buildings, we paint roofs, we paint fences especially iron fences to stop them from rusting , artists use paint to make paintings, people use paint to make signs which are informative, we paint road signs on the road to tell cars where to go.

We have just seen that processed materials can be used because they have special properties such as paint having the ability to change an object's colour. In the last chapter we looked at concrete. We learned how to make concrete by combining different materials.

But concrete can also be used decoratively as it has many different textures. Look at the pictures below which give some idea of the different textures of concrete and how it is used to make surfaces look interesting! A fun activity here would be to take learners on a walk around school to see how many different textures you can identify on the buildings, paths, pavements, etc. They can make rubbings using pieces of paper and pencils or wax crayons. That is right Tom!

And there are so many more properties that we could discuss, such as being fire resistant! But the best would be for you to go out and experience it for yourself and look at the materials around you with new eyes! This can be used as a possible project where learners have to present their findings either in the form of a poster, a pamphlet or an oral to the class. Encourage learners to experiment with drawing, and even making rubbings of different textures.

You can use some time in class for learners to walk around the school and classroom to investigate the materials used, and some part of the project can be set as homework to look at the processed materials in their homes and communities. This activity could also be combined with their other subjects like Art use the rubbings to create an artwork or Language oral presentation.

In the next section we will learn about some of the ways in which people processed materials in early times. Some of these traditional methods of processing materials are still used today! This section is quite reading-intensive. There are two rather long stories about the Khoikhoi youngster, Heitsi, that describe various methods of traditional processing.

The stories have been written in such a way that they are factually correct, and so they may link well with other learning areas such as Life Orientation or Social Studies. One idea would be to use these stories as comprehension pieces. Depending on the reading level of your learners you may choose to read it to them, or let the learners each read a paragraph in turn. It is a requirement of CAPS that 'learners should read, write, draw and do practical tasks regularly'.

Another idea may be to allow learners to act out the two stories about Heitsi and his family. An important cultural message to bring across is the resourcefulness of our ancestors, and how they used what was available to make their lives more comfortable.

People have been processing materials from the earliest times. In the old days only natural materials were available and people found many clever ways to make these materials more useful. The first people who lived in our land had ways to harden wood and bone for making tools and hunting weapons.

They also had ways of reinforcing the mud used for making traditional huts. They knew which materials made the best clothes and blankets, and which grass made the softest beds. They also knew exactly which reeds would make the best mats to cover their walls, and how to build houses best suited for their climate and lifestyle.

Some of these traditional ways of processing materials are still used today. In this section we will learn more about them. Before South Africa was a country, several interesting groups of people lived in our land. The Khoikhoi people were one of the first nations to live in Southern Africa and many modern day South-Africans are descendants of the Khoikhoi. The Khoikhoi were pastoral people who kept goats, but also hunted animals for their meat and skins.

Heitsi is getting his hunting kit ready for the hunt. He is not a man yet, but already a good hunter. When he was born, 11 summers ago, his mother named him after Heitsi-eibib, who was a mythical hunter, sorcerer and warrior in the stories of his people. His father and uncles have taught him how to use the traditional hunting weapons of the Khoikhoi: the bow and arrow and the "kierie" throwing stick.

Heitsi is very excited about the hunt. Today he is hoping to kill a springbok, because he wants to cut a head dress for himself from the skin of the springbok. He can already imagine how envious his friends will be when he wears it proudly around his head.

He will give the rest of the springbok skin to his mother to turn into a blanket karos or a piece of clothing for his new baby sister. His mother will scrape the skin with a sharp stone or metal blade to remove the hair and rub it with animal fat for a long time to make it soft. Heitsi slings the quiver in which he keeps his arrows over his shoulder. The quiver is made from tree bark. It is a good quiver, but he really wants one made of animal skin like the one his father carries.

The arrows inside the quiver have wooden shafts and sharp tips made of metal. His younger cousins have arrows with tips made of hardwood. In the old days all the arrow tips were made of wood or bone, but Heitsi's people have been making contact with other peoples who have introduced them to metal. He also keeps some tinder in his quiver. Tinder is the name for the soft, dry plant materials his people use when starting a fire. Another item he keeps in the quiver is a hollow reed that can be used like a straw to suck up water that has collected on the leaves of plants.

He knows that he has to handle the arrow tips very carefully because they are very sharp. He keeps them sharp by rubbing them on a special stone.

Another reason why Heitsi handles the arrows very carefully is because their tips have been covered with a layer of poison. His cousins sometimes use the sap from poisonous plants to treat their arrow tips, but he prefers to use snake poison because it is more potent. He picks up his bow, and admires it for a moment. He made it himself from the flexible wood of a wild olive tree. The bow string is made from the gut of a small wild cat that he hunted last summer. His uncle's bow has a string made of twisted palm leaves, and it makes a beautiful sound when Uncle holds the end of the bow in his mouth and taps against the string with a stick.

Tonight, when they return from the hunt, the men will dance around the fire while the women sing and clap their hands. There will be stories told about the hunt, and Heitsi will honour the soul of the springbok that he has killed. The last weapon he picks up is his kierie. It has a long handle and a knob at the top end. The kierie was a gift from his favourite uncle. Uncle made it himself from strong wood. To make the kierie even stronger, Uncle placed it close to the fire for a long time.

The heat from the fire dried out the wood and made it tough and strong. Later, we will read about the traditional Khoikhoi house that Heitsi and his family lived in. First, we will learn about a different kind of traditional home, that is still seen today.

Some of the traditional homes in Africa are made of clay or mud. In the activity Making Bricks , we saw that mud a mixture of soil and water is not a very strong material. When it is dry, it can crumble and collapse. He paper is made from pulp with various additives to control the physical characteristics, printability and aesthetics of the finished product.

Today, most of the paper is made from wood pulp mostly spruce or pine. However, cotton, flax, straw, bamboo and hemp fibers may be used. Glass makers add chemicals soda ash and an accelerant such as potassium nitrate to silica sand to bring it to temperatures around F.

Then add small amounts of metal to change the color and give the shape in hot to finally let it cool. Another example of processed materials is bronze. This material is a stronger copper and tin alloy than any of its two components. Their discovery had such a large effect on history that the time period in which they were first used was known as the Bronze Age.

Steel is an alloy of iron and carbon. This alloy is one of the most widely used processed materials. This material is made from large and small animal skins. The use of animal skins is one of the oldest technologies of man, perhaps even before the manufacture of tools. Plastics are an important example of this. The more processed a material is, the more likely the material will create problems of waste disposal.

This activity aims to introduce students to a range of natural and synthetic materials and promote discussion about the enhanced properties of synthetic dyes.

Students could also discuss and identify some of the disadvantages of synthetic dyes in comparison with natural dyes, such as waste disposal, safety handling issues and allergies.

Assemble a number of natural foods which have a strong colour and could be used as possible sources of natural dye such as beetroot, blackberries, saffron, red currants, raspberries and flower petals and purchase a few commercial synthetic cold water dyes. Prepare a range of clothing samples from both natural and synthetic materials such as cotton, silk, nylon, terylene and polyester , identify each and place samples into the containers with the different dyes.

Leave these for a couple of days and then using gloves remove them and rinse them under cold water and air dry. Encourage the students to evaluate how effective the natural and synthetic dyes were in creating a permanent colour change in the cloth. Which of the natural materials were most affected by the dyes and which ones appeared to fade when washed? Discuss the advantages and disadvantages of natural and synthetic dyes and their ability to effect colour fast changes in a range of different materials.

This activity aims to encourage students to identify and discuss the physical properties of a range of materials and suggest on the basis of the properties identified how they could be best used. Collect and introduce the class to a range of natural and processed materials. Avoid presenting them with easily identifiable objects designed for a specific purpose such as a building brick. Encourage the class to identify a number of individual properties associated with each material and then invite them to select a material best suited for a specific task.

For example, assemble a number of small pipes or tubes made from the following materials: glass, PVC, cardboard, metal, ceramic and bamboo.