Unit Nine

Introduction

The aim of this unit is to revise and learn to describe materials and their properties. You will practice making definitions. Explain and give reasons for using different materials for different purposes.

Objectives:
After this unit you should be able to:

• understand and describe properties of different materials,
• make definitions,
• explain the reasons for using a material,
• give the reasons for using a material.

Tasks and Dates

This unit consists of five activities.

To complete this unit you should go thought all activities. Contribute to all forums at least once. Go thought the quizzes.

Making definitions

First, look at the table below and complete it using the words from the list. Then go to “Materials” quiz to check your answers.

MATERIALS
Metals		Plastics		Woods		Textiles
ferrous	non-ferrous	thermosetting	thermoplastics	natural	manmade

acrylic, mild steel, pine, mahogany, oak, threads, polythene, aluminium, stainless steel, wrought iron, copper, brass, polyester resin, melamine formaldehyde, polyvinyl chloride (PVC), fabric, dyes, silk, wool, cotton, chipboard, plywood

Now you are going to read an article about KEVLAR® . Read the text in the “KEVLAR” quiz and answer the questions.

After that, listen to the recording in “Material properties” quiz. You will hear some definitions. Put the material properties in the correct order. Practice your pronunciations listen to the words in the “Pronunciation” quiz and repeat.

Then, study the language used for making definitions in the box bellow and complete the “Properties” matching quiz.

Finally, go to the “Definitions” forum. Make your own definitions for the words below (explain them). Use defining relative clauses.

composite __________________________________________________________________

alloy ______________________________________________________________________

lightweight _________________________________________________________________

manmade __________________________________________________________________

thermosetting plastics ________________________________________________________

ferrous metals ______________________________________________________________

Giving reasons

First read the two texts below and complete the tables.

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Canoe Materials

Wood Canoes: (high cost, high maintenance)
Recent innovations such as watertight epoxy coatings, improved varnishes and modern production methods have made these canoes lighter, faster, and most importantly more durable than ever before.

Aluminium Canoes: (moderate cost, no care)
Aluminium canoes are corrosion-proof, sturdy, require little maintenance, and do not deteriorate when exposed to sunlight. They are the only canoes that can be left outside and ignored all winter. The disadvantages as well as being heavy, aluminium canoes heat up quickly in the sun and cool off in the cold. They are noisy.

Fibreglass Canoes: (low to moderate cost, minor care)
Fibreglass is the most common material used in manufacturing canoes. The quality of fibreglass canoes can vary widely from excellent to poor. The major difference is; good quality fibreglass canoes are made by laying strips of fibreglass cloth into a mould saturated with resin. Poor quality fibreglass canoes are made using small separate pieces of fibreglass called "chopped fibre" in place of the stronger, more expensive fibreglass cloth.

Kevlar Canoes: (High cost, moderate care)
Kevlar canoes are rapidly becoming more popular each year due to Kevlar’s great strength to light weight ratio. Kevlar produces a lightweight canoe with minimal compromise to strength and durability. With a strength per weight ratio marketed as being "stronger than steel" making boats of this material very impact resistant.

Carbon & Carbon/Kevlar Canoes: (highest cost, high care)
Carbon is the latest advancement in canoe building technology. Carbon is slightly lighter, stiffer, and is less flexible than Kevlar. When bonded with Kevlar, carbon tends to hold its shape better than other materials - keeping lightweight boats from flexing out of shape. Its primary use is in building the lightest possible performance oriented performance and racing boats. Carbon canoes are lighter but are not as strong as Kevlar canoes.

Polyethylene & ABS Canoes (low cost, low care)
"Plastic, Tupperware and Poly" are just some of the confusing terms used to describe Polyethylene canoes. Polyethylene is extremely tough, but as a soft material is not very rigid. Manufacturers have overcome the stiffness problem in different ways. Some companies brace their canoe interiors with aluminium tubes and struts. This makes a heavy, clunky but acceptable canoe. Other companies continue to produce canoes from single layer polyethylene by adding a keel in a largely unsuccessful attempt to stiffen. Single layer poly canoe hulls tend to "oil-can" and lose shape quickly when paddled. The most successful solution is a patented multi-layer "sandwich approach". A thick foam core is sandwiched between an outer and inner layer of polyethylene to provide stiffness at moderate cost

Royalex & Royalite Canoes: (moderately high cost, minimal care)
These canoes are manufactured in a similar fashion to a quality polyethylene canoe using the "sandwich method". A lighter core is sandwiched first by thin multiple layers of ABS substrate for stiffness, then finished by adding a vinyl inner and outer skin. Royalex canoes weigh less, are more expensive, but are not as strong as a "sandwich" method polyethylene canoe. Royalex canoes with vinyl gunnels are very difficult to damage as they tend to "pop back into shape" better than other materials. Serious white-water paddlers requiring a canoe which is lighter than Polyethylene often choose Royalex. Royalite is simply a thinner, lighter, but more fragile version of Royalex.

Source: Adapted from http://www.frontenac-outfitters.com/onlinetutorials.cfm?id=2

Material	Reason for using it
wood
aluminium
fibreglass
Kevlar
Carbon & Carbon/Kevlar
Polyethylene & ABS
Royalex & Royalite

Then study the ways of describing reasons for an improvement, a design change or choice of materials.

Choose three materials and reasons from the table and make sentences. Use all the ways given in the box. Upload your sentences to the “Reason” forum.

Finally go to the “Listening – test practice “ quiz and complete it.