# Solid materials

• What kinds of materials are solid objects made from?
• What is the difference between raw and manufactured materials?
• Where do raw materials come from?
• Is sand really made from glass?

In the previous chapter, we looked at materials all around us and how they can be either a solid, a liquid or a gas. Now we are going to look more closely at solid materials.

In CAPS, this section has been allocated two weeks (7 hours), however, more time might be needed, possibly three weeks. The next chapter on "Strengthening Materials" could possibly take a shorter amount of time than two weeks, possibly one week. So, a suggestion is to spend more time on this chapter and a bit less time on the next chapter ("Strengthening materials"). there are also some activities in this chapter on flexibility which could be repetitive and so if you do not have time to do all of them, then just choose one.

## Solid materials all around us

Almost everything around us is made of materials. The shoes you wear, the pen you write with, the glass you drink out of, cellphones, a soccer ball, all your toys, the chair you sit on are all made of materials.

# Investigating materials that objects are made from

INSTRUCTIONS:

1. Study the object below and answer the questions that follow.

QUESTIONS:

What is this object called and what is it used for?

A pencil bag is used for keeping your stationery in.

What material is the object made of?

Fabric

Do you think this is a good material for this object? Give a reason for your answer.

Learner dependent answer - check their ability to provide a viable reason to justify their answer.

Can you suggest another type of material that can be used to make this object? Do you think this material will work better? Give a reason for your answer.

Learner dependent answer - a possible material to make it from is plastic, which might be stronger for example.

The object has a zip. What is the function of the zip?

To open and close the bag

What material is the zip made from? Do you think this is a good choice of material? Give a reason for your answer.

The zip is made of metal. It is a good choice of material as metal is strong and will not break when you are constantly opening and closing the zip. Assess what the learners says and if they provide any other reasons.

In the previous activity, you should have learnt that:

• We use materials to make useful objects.
• We choose materials for a specific purpose when we make the object.

In the next section we are going to see how some materials are used to make new objects. We are also going to look at why some materials are better to use for making certain objects.

## Raw and manufactured materials

Every day we use different products made from different materials. The chair you are sitting on is made of a material called wood or plastic. Wood is from a tree. Wood comes from a natural resource. It can be used as a raw material by humans to make furniture.

### What does raw and manufactured mean?

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.

Sheep are farmed for their wool. Wool is a raw material, but it is processed to make a manufactured material. What things are made from wool?

Fabric, jerseys, scarves, socks, beanies, gloves, etc

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

### Examples of raw materials used to make other materials

• 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.

# Describing the properties of raw and manufactured materials

Photos are provided but it would be best if you could bring some of the actual materials into class, such as wet clay and a fired clay pot.

INSTRUCTIONS:

1. Below are some of pictures of the raw material and the manufactured product that is made from the raw material.
2. Study these pictures and compare the properties of the raw material and then the manufactured material after it has been processed.
 Animal skin (hide) is used to make leather. Boots made from leather. Describe the properties of the cow hide: Describe the properties of the leather:
 Wool from sheep is used to make to make clothes. Wool is spun to make strings and dyed to make it colourful and will be made into clothes by knitting. Describe the properties of the sheep wool: Describe the properties of the processed wool:
 Clay being moulded into a pot.http://www.flickr.com/photos/kellinahandbasket/2183799236/ A pot made from clay which has been painted Describe the properties of the clay: Describe the properties of the ceramic pot:
 Sand is used to make glass. http://www.flickr.com/photos/sroown/797820971/ Glass is made from $$\text{70}$$% sand which has been heated to very high temperatures. Describe the properties of the sand: Describe the properties of the glass:

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.

# Classifying materials into raw or manufactured

INSTRUCTIONS:

1. Look at the pictures in the table below. How can we tell whether something is a raw or manufactured material?
2. Classify the objects into one of the groups, raw or manufactured material, by placing a tick in the right column
 Object Raw material Manufactured material Watermelon http://www.flickr.com/photos/jetalone/201784099/ tick Glass tick Feathers tick Coins tick Diamond Tick (tricky as this diamond has been polished and cut to look like this, but diamonds do occur naturally) Pot made of clay http://www.flickr.com/photos/aloha75/6086355519/ tick Plastic bag tick Wood http://www.flickr.com/photos/tuchodi/5040332553/ tick Sand tick

### The paper story

Introduce the topic by highlighting the role paper plays in everyday life. Let the learners list objects made of paper. How do they feel about framed photos of loved ones? Ask them where paper comes from. Let them read the story below and then answer the questions.

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.

What raw material is used to make paper?

Plant fibre

You can supplement the following activity with other resources from paper mills such as Sappi and Mondi which will have brochures for children about the papermaking process.

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!

Learners generally struggle with a flow diagram - the concept that one thing happens after the other. Teachers need to explain this concept carefully and show learners that a flow diagram lays out all the steps in a process in the order that they happen in. Perhaps, first just get learners to look at the flow diagram whilst you go through the accompanying notes, and then they can read the notes themselves and match each note to the picture it is describing.

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.

# The Papermaking Process

INSTRUCTIONS:

1. Read through the diagram again that the Thunderbolt Kids were given at the paper mill and the notes that Tom wrote down

QUESTIONS:

What are some of the final products that paper can be made into?

Books, newspapers, magazines, billboards, toilet paper

Which type (species) of tree is mostly used to make paper?

Eucalyptus (gum trees) and pine trees

Plant fibre and water

What does "debarked" mean?

It means the bark is removed from the logs.

What is a landfill site?

It is where the rubbish is dumped in big areas.

Arrange the processes in the process of papermaking in the correct way.

A. Chips go into the pulp mill.

B. Wood logs are transported by trucks.

C. Pulp flows to the paper mill.

D. Paper is transported to buyers who make other paper products.

E. The pressed and dried pulp is rolled or cut into sheets as paper.

F. Wood is harvested from trees growing in a plantation.

G. Pulp is washed, bleached and cleaned and dried.

Answer: F, B, A, C, G, E, D

Talk to a partner about the section of the papermaking process that interested you most. Explain why you find it interesting.

Do you think many people work in the papermaking industry? Explain your answer.

Many people are employed. There are job opportunities for workers in the forests at the paper mills to transporting products etc.

Do you think the papermaking process is a long or a short process. Give a reason for your answer.

It is a long process as there are many steps involved which all take time, especially the growing of the plantations as the trees take several years to grow to the right height.

Name 2 of the major papermaking companies in South Africa that you know of.

Sappi and Mondi

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.

Is there a paper recycling project in your school or environment?

Yes/no

Why do you think we need to recycle paper?

Energy is saved to make new paper products when using recycled paper. Reduce the waste at the landfill sites which have a big environmental impact and destroy natural habitats.

## Properties of materials

Raw and manufactured materials have specific properties. We already looked at some of the properties of raw and manufactured materials by describing them. The properties of a material help determine how it is used. For example, plastic is waterproof so some rain jackets are made of plastic to keep the rain off and keep you dry. A rain jacket made from wool or fibre would not be waterproof and you would be soaked! This is because the wool is an absorbent material (it absorbs water).

### Hard or soft?

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.

# Exploring the hardness of materials

MATERIALS:

• asharp steel nail
• a wax candle
• a metal coin
• a plastic spoon or wooden pencil

INSTRUCTIONS:

1. First make a prediction about whether you think you can scratch or dent the object. Fill your predictions in the table.
2. Scrape the point of the steel nail across the surface of the wax, the metal and the plastic
1. Fill in your observations in the table below
2. Try to indent (make a dent in) each of the objects by pushing the point of the steel nail into each of the objects
3. Fill in your observations in the table.
 Material Prediction - can you scratch or dent the material? Scraping observations Denting observations Wax candle Metal coin Plastic rod

QUESTIONS:

Which of the three materials is the hardest?

Metal coin

Which of the three materials is the softest?

Wax candle

### Tough or fragile?

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.

# How tough are some materials?

You could use this scientific investigation to answer the question that you write on the board, learners then come up with a hypothesis, and you then present them with the apparatus and they try come up with the method themselves to test their hypothesis. Do not work from the workbooks. Then once learners have had a chance to design their own investigation, you can come back to the workbook.

AIM: To investigate how tough different materials are.

APPARATUS (Each group will need:)

• 1container with a wide round opening (eg. large jam tin, yoghurt container)
• 1 square sheet (20 cm by 20 cm) of each of the following materials:
• newspaper
• photocopy paper
• tin foil
• wax paper
• plastic wrap
• 2 thick elastic bands to fit around the container
• a meter stick or tape measure
• a metal teaspoon

METHOD (Each group will have to):

1. Choose a material to test
2. Place the material over the top of the container and hold the material in place using the elastic band. Make sure that the material is flat and secure.
3. Hold the covered container next to the meter stick.
4. Hold the teaspoon by the handle 10 cm above the top of the container.
5. Drop the teaspoon straight down onto the material
6. Record your observations in the table below (Did the material dent, tear?)
7. If the material did not break repeat the experiment by dropping the teaspoon from 20 cm above the material. Record your observations.
8. Keep increasing the height from which you drop the teaspoon by 10 cm until the material breaks.
9. Remove the broken material and replace with a different material.
10. Repeat the experiment.

Setup:

RESULTS AND OBSERVATIONS:

Record your measurements and observation in the table. :

 Material Final drop height (cm) Observations newspaper photocopy paper tinfoil wax paper plastic wrap

CONCLUSION (What you learnt):

The energy of the teaspoon when it hits the material depends on the height from which you dropped the teaspoon. The greater the height the greater the energy. The toughest material only broke with the teaspoon with the greatest energy.

1. Which material broke first and which material broke last?

2. Which material needed the least amount of energy to break?

3. Which material took in (absorbed) the most energy before breaking?

4. Which material was the toughest?

Energy will only be dealt with in Term 3, and these questions require learners to connect height when the plastic wrap breaks with energy. But this can be picked up again next term and provides a nice extension.

### Stiff or flexible?

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.

Fill in the table with your ideas of stiff or flexible materials and where they could be used. Look around your classroom or home and find 3 more materials which you must add in the empty lines and also classify.

 Material Stiff or flexible Where would material be useful? rubber glass wood plastic material

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!

Teacher note: When doing scientific investigations it is VERY IMPORTANT to not simply state the steps in the scientific method as learners will then just want to memorize the steps. Also, asking learners in a test to simply write down the steps in the scientific method does not add to their understanding of why we need them. They are simply recalling. Understanding why each step is needed and the logic of the steps comes with time and more practice. What we want learners to be able to do is ASK TESTABLE QUESTIONS, HYPOTHESISE and then DESIGN and CONDUCT EXPERIMENTS to test their hypotheses and thereby answer the question. The following questions will help learners come up with the question, hypothesis and prediction for the ruler investigation. You need not only use investigations which are outlined in these books, but actually TEACH learners how to go about doing an investigation. The procedures outlined in these workbooks will help, but rather do not use the book to follow a step by step procedure. Use it to guide your teaching in class while the learners' books are packed away and the learners have to come up with their own design and see how they can best conduct the experiment using the apparatus available. Refer to the books later to consolidate the investigation and record results. Each time you teach a different investigation you can also focus on a different aspect, such as asking the right investigative question, OR formulating an hypothesis, OR learning what variables are, OR representing data. Each of these skills will be emphasized in different ways in the different investigations, but only choose ONE to focus on at a time. This also will not all take place in one year, but the skills will be built up gradually over the years at school.

What did Tom observe?

What was the question he wanted to answer?

Which ruler is most flexible, a ruler made of wood, plastic or metal?

Why did the class do the experiment? This is the aim of the experiment.

To find out which ruler is most flexible.

What do you think the answer is to the question in number 2?

Dependent on learner.

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

Which material is the most flexible for a ruler?

Teacher note: It is probably best to test the experiment yourself first to see if the 500g mass is sufficient to cause the rulers to bend. If not, you might need a bigger or smaller mass. Also, if you do not have a clamp, an alternative could be to rest a very heavy object on the end of the rulers such as some books or a pot plant.

APPARATUS (What you will need):

• 30 cm plastic ruler
• 30 cm wooden ruler
• 30 cm metal ruler
• 500 g mass
• string
• clamp

METHOD (What you have to do):

1. Set up the apparatus as shown. The ruler must be clamped on to the end of a table.
2. Measure how far the mass pulls the end of the ruler down and record the distance in the given table.
3. Clamp the next ruler in exactly the same position and measure how far the mass pulls the end of the ruler down.
4. Repeat with the last ruler

RESULTS (recording what you observed and found out):

 Type of Ruler Distance moved down by the end (cm) a. b. c.
1. Which type of ruler allowed the mass to move the furthest?

2. Which type of ruler allowed the mass to move the least distance?

3. If the mass is able to move down, then it means the ruler has to bend. We have said that the measure of how much something can bend is its flexibility. Which ruler do you think is the most flexible and why?

CONCLUSION (what you learned from the results):

What did you learn from this investigation? Provide an answer to your original question.

From your own conclusion, explain to Tom how you decided which ruler is most flexible.

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.

The next investigation follows on from the previous one. This shows how when you conduct a scientific investigation, more questions can come from it, which you can then attempt to answer again with another scientific investigation. If time does not permit you to do this investigation as well, you could leave it out, or possibly rather have a class discussion about how to design an experiment to answer this next question of how flexible one ruler is. However, this next investigation provides an opportunity to plot a graph so the focus of this investigation is to teach learners how to draw graphs.

# Investigating the flexibility of a ruler

APPARATUS (What you will need):

• 30 cm flexible ruler
• clamp
• string
• any ruler
• six (6) 100 g mass pieces
• graph paper

METHOD (What we have to do):

• Use the most flexible ruler and set up the apparatus as in the previous experiment.
• Hang a 100 g mass piece on the end of the ruler. Use any other ruler to measure how far the end drops down. Record the distance dropped from the start in the table.
• Add another 100 g mass piece and record the total distance the end drops down.
• Repeat step 3 until 600 g are hanging from the end of the ruler.

RESULTS (what you observed):

 Mass (g) Distance dropped from start (cm) 100 200 300 400 500 600

Use the results from your table to plot points on graph paper. We decided to change the mass hanging to the end of the ruler. With each mass the distance dropped changed. When plotting a graph the quantity we chose to change (in this experiment, we changed the the mass) is plotted on the x-axis.

• Draw the x-axis, label it and choose the scale.
• Draw the y- axis, label it and choose the scale.
• Draw a line graph using your plotted points to guide you.

Do not join the plotted points with a ruler. A smooth line drawn freehand through all the points is important

CONCLUSION (what you learned):

Which mass piece made the ruler bend the most?

The heaviest

Which mass piece made the ruler bend the least?

The lightest

What can you conclude about the distance the ruler moves (bends) and the mass that is hung from the end?

The heavier the mass the more the ruler will bend.

Further activities to investigate the properties of solid materials, such as light or heavy and waterproof or absorbent, is to bring some of these materials to school and let learners experiment with them in class. For example, bring some polystyrene balls and some marbles and some metal ball bearings which are all roughly the same size. let learners hold and play with them to see how they are very different in their weight although they may be similar sizes. You can put a bowl of water in front of the class and ask learners which balls they think will float and which will sink and then do the demonstration. (The polystyrene balls should float and the other two will sink). To investigate waterproof and absorbent, bring some sheets of these different materials to class, such as a dish cloth, a scarf, a piece of plastic (black bag or shopping bag), a piece of canvas, a piece of waterproof material to make jackets (if possible). Set up a demonstration in front of the class again and ask learners whether they think the piece of material will let a cup of water run through it (or if it will be able to soak up or dry some water on a saucer. Once they have answered you, do the demonstration to see if they are correct. You could get two learners to hold the piece of the material so that it makes a kind of cup or container and then you pour the water in. The rest of the class watches to see if any water comes out of the bottom and how much or how quickly. These kinds of activities will reinforce the idea of first asking a question, making a prediction and then testing it to see if your prediction was correct.

### Extension: Strength in tension

Teacher note: This is an EXTENSION and can be done if time permits or if you have some learners who are further along than others.

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.

# Identifying different materials that are strong in tension

INSTRUCTIONS:

1. In each of the following scenes, identify the material that is strong in tension (pulling forces).
 Scene Material that is strong in tension 1. A person carrying a plastic shopping bag full of groceries http://www.flickr.com/photos/yourdon/4364551103/ plastic 2. A gymnast on a beam wood or metal 3. A child on a swing http://www.flickr.com/photos/digitizedchaos/4898296156/ steel chains 4. The cable car on its way to the top of Table Mountain reinforced steel cable 5. A parachutist falling under a parachute synthetic rope

When deciding which material to use, it is important to consider the type of material, the size of the material, the shape of the material and the forces the material will experience.

## Different materials for the same object

The use of the object determines the type of material it should be made of. Imagine a bicycle with wooden wheels. Do you think the wheels will turn and work as well as steel and rubber? Materials are chosen and used for the properties they have.

# Identifying different materials

INSTRUCTIONS:

1. Look at the pictures of different chairs below . Even chairs can be made from many different materials (plastic, wood, metal, canvas, etc) or a mixture of more than one material.
2. Identify the types of materials that each chair is made from.
3. Write down where that material comes from.
 Chair Main materials used Where the material comes from Wood From trees http://www.flickr.com/photos/54400117@N03/5069063990/ Fabric From cotton and wool Plastic From coal and oil Metal From metal which has been mined and processed Fabric and wood From trees and cotton plants

Similar objects, such as balls used in sport, can be made from very different materials, depending on what the object is used for. Let's have a look in the next activity.

For the following activity, photos are supplied of the two balls, but it would be ideal for learners to touch and feel each ball. If you can obtain some of these balls, then bring them to your class. The underlying skill of this activity is to describe what you see, in other words, making observations and being able to write them down.

# Activity: Linking different materials with the purpose of the object

INSTRUCTIONS:

1. Work with a partner to complete the activity below.
2. Study the pictures of the balls and then answer the questions.
3. If you have some of these balls, study each one by rubbing it, pressing it and feeling the texture.
 Ball A Ball B

QUESTIONS:

What sports are these balls used for?

A: Tennis, B: Cricket

Each ball is made from a different material. What are these materials?

A: Tennis ball is hollow made from a layer of rubber on the inside and surrounding it is a softer felt-like material.

B: The cricket ball has a solid cork centre surrounded by hard leather and stitched with a thread.

Observe and then describe the properties of the material which is used in each ball.

Tennis ball - soft, "furry"/rough, can dent it (the rubber is flexible), light. Cricket ball - hard, heavier, smooth, shiny.

Why do you think the material was chosen for each ball?

The tennis ball needs to be soft and to be able to bounce as it is hit across the tennis court. The materials the ball is made of help it to do this. The red cricket ball is harder. The leather is smooth and hard and helps the ball to go fast and be hit far.

• Raw materials are those which have not been processed and they come directly from natural products.
• Manufactured materials have been made from raw materials
• Raw and manufactured materials have specific properties
• If a material is hard, it is strong and tough to scratch or break
• If a material is stiff, it is firm and does not bend easily. Stiff is the opposite to flexible.
• Other properties to describe materials are: strong, weak, light, heavy, waterproof and absorbent.

Match the columns below with the raw material and the manufactured material that it is made into:
 Raw material Manufactured material 1. Sand A. Ceramics 2. Clay B. Leather 3. Coal and oil C. Glass 4. Animal wool D. Paper 5. Wood and plant fibre E. Plastic 6. Animal hide F. Fabric

1: C

2: A

3: E

4: F

5: D

6: B

What is the term used for a material which is not flexible?

Stiff

What is the term used for a material which is not waterproof?

Absorbent

Choose three materials that you would use to build a chicken run (an enclosed yard for keeping chickens). State at least two properties of each material and how those properties would help in making your chicken run to be safe from animals and weather elements. Use the space below to draw a table for your answers.

 Materials Properties Wire mesh Flexibility, Toughness Wooden poles Stiffness, Strength in tension Zinc roof metal-sheets Hardness, Toughness