Where have you heard the word "raw" before? Perhaps it was when someone was talking about your food and they said the meat or vegetables were still raw as they had not been cooked yet. When we talk about raw food, it means the food has not been processed by cooking. When we process something we do something to it to turn it into something else with different properties.

We can also talk about raw materials. This is when the material is in its natural state. It has not been processed yet. We find raw materials in the environment around us, such as the trees in a forest, or coal and oil underground. But, when this raw material has been processed, meaning humans have changed it, then we call it a manufactured material.

Examples of a raw materials are wood and plant fibre. Once wood and fibre have been processed, humans make it into paper. Paper is a manufactured material.

Raw materials in our environment are used to make other materials which are very useful. Let's look at some.

• Animal skin is a raw material and is processed into leather to make shoes, handbags and belts.
• Animal wool is used to make clothes, such as jerseys and scarves
• Sand is a natural, raw material. Sand is heated to extremely high temperatures and melted to make glass.
• Clay is moulded and burned to make ceramics, such as teacups, teapots and vases.
• Coal and oil are used to make plastics, paints and fabrics.
• Wood and plant fibres are used to make paper.

Look at the pictures in the following activity which show the raw material and the manufactured material that is made from each. Raw and manufactured materials have different properties.

We know that materials are used to make different objects. You have now learned that some materials are called raw or natural materials and some are called manufactured or man-made materials. We can group matter according to how it is used. This grouping of matter is called classifying.

Can you imagine a world without paper? There would be no books, newspapers, magazines or even a sheet of music when you want to play piano. No paper means no more paper food labels or paper packaging. Not even toilet paper or kitchen wipes.

Paper is a very important material in our lives today. Let's find out how paper is made.

Paper is made from the wood and plant fibre from trees growing in plantations all over the world.

Afield trip with the Thunderbolt Kids!

The Thunderbolt Kids had just been learning about paper in their class. Tom wanted to know more about how plant fibres from trees are actually made into paper. So, the Thunderbolt Kids decided to visit a paper mill to learn more about the life cycle of making paper.

They were each given a diagram to help explain the papermaking process. You have also been given a copy of the diagram. The processes that take place at each stage were explained to the Thunderbolt Kids at the mill and Tom wrote down his notes. You will see his notes below for each stage - make sure you read these too!

Tom's Notes:

1. Plantation

   • Trees are planted in well-managed forests. These are called plantations.
   • The trees are allowed to grow for several years before being cut down.
   • The main types of trees used to make paper are the Eucalyptus (gum trees) and Pine trees.

2. Harvest

   • Once the trees reach a certain height they are cut down. This is called harvest.
   • The logs are cut into smaller pieces so that they can be transported.

3. Transport

   • The logs are all loaded onto big trucks and transported to the mills.

4. Pulp mill

   • The logs are first debarked, meaning all the bark is taken off, and then chopped up into smaller pieces, called chips.
   • The chips are mixed with water and other chemicals to make a soft pulp.
   • Pulp consists of wood fibres and water.

5. Paper mill

   • The pulp then flows to the paper mill.
   • At this mill the pulp is washed, bleached and cleaned before the paper is made.
   • The pulp is pressed and dried and then rolled or cut into sheets of paper.

6. Printers

   • The paper is transported to other buyers and printers in big rolls.
   • These printers make the paper into other products such as books, magazines and newspapers.

7. People

   • The finished products are transported to shops where people buy the products.
   • When people are finished using the paper products, such as reading a newspaper, they throw it away in the dustbin or recycle it.

8. Paper sorting

   • All the rubbish paper is collected after it has been thrown away and it is sorted.
   • Some paper can be recycled, but some cannot, so the paper is sorted into two different groups.

9. Recycling

   • Used paper can be collected and used again. This is called recycling.
   • The paper that can be recycled is converted into other products.
   • Or it is made into recycled fibre which can then be used at the paper mill again.

10. Landfill

    • Paper which cannot be recycled is taken to the landfill sites where it is dumped.
    • Landfill sites have a negative impact on the environment, so it is best to try hard to reduce the amount of waste which ends up at landfill sites by recycling.

After the field trip, Sophie was really interested in how she could set up recycling at their school to help reduce their impact on the environment. Farrah showed her arty side when she made some earrings and a cover for her notebook from recycled paper. Jojo was just happy that he had his favourite sports magazine to read, which is made from paper. And Tom was really happy that he got to learn more about the papermaking process.

We mentioned recycling as a part of the papermaking process. Recycling is a very important process as it allows us to reduce our waste and use things over again. Not only paper can be recycled. You can also recycle glass, tin and plastic.

A material is described as hard when you cannot scratch it, you cannot cut it and you cannot dent it. Hardness measures how difficult or easy it is to change the shape of the material, either by denting, cutting or scratching it. A diamond is an example of a hard material as diamond cannot be scratched by other objects. In fact, diamond is so hard it is used in drill bits to drill through rocks and many other materials.

The opposite of hard is soft! Think of the wet, raw clay from the previous chapter. This clay is soft and can therefore be moulded into a new shape.

A material is tough if it is hard to break. Kevlar is used to make bullet resistant vests. This material makes it very difficult for bullets to go through.

If you hit a metal coin with a hammer, there will be no or little damage. If you hit a piece of chalk with a hammer it will break into pieces. The metal coin is tough compared to the chalk. The chalk is very fragile.

Toughness measures how much energy is needed to break a material. We will test some everyday materials to decide which material is the toughest.

Stiffness and flexibility are ways of describing how an object behaves when a force is applied to it. A stiff material will not bend when you apply a force (push on it). But a flexible material will bend. When builders choose materials for building structures, sometimes they need flexible materials and other times they need stiff materials.

Case study: The flexibility of rulers

The Thunderbolt kids use rulers a lot in class. Their teacher likes them to use rulers to draw straight lines so that their work is neat. Tom needed a ruler as his was broken. Tom noticed that his was broken and so was Farrah's, but Sophie's and Jojo's rulers were not broken. Tom also observed that each of them had rulers made of different materials, either wood, plastic or metal. Tom thought that maybe the type of material that the ruler was made of might influence whether it would break or not. Tom asked his teacher if the material of the ruler made a difference to whether the ruler would break or not. Their teacher suggested that the whole class do an experiment to test the flexibility of the different rulers by doing a science investigation. Science investigations are used to answer questions!

Let us now try answer the question by doing a science investigation.

The class was so excited after doing the experiment to advise Tom which ruler to buy, that they suggested doing another experiment to test how the most flexible ruler behaves when different masses are hung on to one end of it.

Some situations require that materials be strong in compression (be able to withstand pushing forces) and other situations where materials need to be strong in tension (be able to withstand pulling forces).

The vertical (upright) steel poles of the water tower that are supporting a great weight have to be strong in compression in order to hold up the weight of the water tank.

The rope supporting the bungee jumper needs to be strong in tension to ensure that the rope does not break and that the jumper survives his experience.