Speaking
Speak about:
The main parts of any tree and their functions.
Sapwood and heartwood.
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Unit 5
Indefinite, Continuous, Perfect Tenses Passive Voice
Grammar:
Wood as a Raw Material
Wood has always been and still remains one of the most important natural raw materials necessary to man.
Wood has a wide variety of grain pattern, colours and densities. It is easily worked with tools and machines. Unlike many materials, wood is resistant to mild chemicals and insulates against electricity and heat. Indeed, the air inside its cellular structure makes timber the best thermal insulator of all known building materials. That is why wood is widely used in construction and furniture making,
in making refrigerators and cooking utensils.
On the other hand wood can burn. It can be attacked by insects and fungi. It shrinks and swells with changes in humidity.
There are many ways of avoiding deterioration of wood. It can be impregnated with preservatives to guard against biological attack. Flame retardants can protect wood from fire. Chemicals can also be applied to avoid shrinking and swelling. Mechanical and chemical treatment of wood gives products of much higher strength than the wood itself. Fibreboards and particles boards are good examples of such products.
The amount of waste in woodworking industry is several times less than that in mining and metallurgy. Energy requirement for processing wood are also lower. It takes about 1500 kilowatts hours of electricity to produce a ton of sawn timber while the production of the same weight of aluminium requires energy 45 times as much.
Nowadays wood is still often used as a fuel. When wood is burnt we lose 90 per cent of its value. Therefore much research efforts have been made and are now being made to make this useful material accessible for other purposes. New methods of processing wood are being investigated, new ways of getting valuable products out of it are being introduced.
General Understanding
Read the text attentively and answer the following questions:
Does wood still remain one of the important raw materials? Why?
Why is wood widely used as a building material?
What makes wood the best thermal insulator?
What are the disadvantages of wood?
How can deterioration of wood be avoided?
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What can increase the strength properties of wood?
What other advantages of wood as a raw material are mentioned in the text?
Is wood still used as a fuel?
Is it rational to use wood as a fuel? Why?
What is done to make this valuable raw material accessible for other purposes?
Vocabulary
Exercise 1. Match the English words in A with their Russian equivalents in B.
A 1. raw material 2. grain 3. density 4. insulator 5. resistant 6. shrink 7. swell 8. deterioration 9. subject 10. humidity |
B 1. устойчивый 2. подвергать 3. сырье 4. плотность 5. усыхать 6. влажность 7. изолятор 8. текстура 9. ухудшение, порча 10. разбухать |
Exercise 2. Find the English equivalents to the following Russian.
разнообразие; обрабатывать; клеточная структура; мебель; гореть; грибки; насекомые; пропитывать; антисептик; защищать; огнестойкая добавка; отходы; количество; переработка; требовать; терять.
Exercise 3. Choose the words from the text which have the similar meaning.
figure; diversity; weak; heat insulator; cabinet making; durability; to permeate; to use; to prevent; quantity; needs; available.
Exercise 4. Fill in the blanks with the words from the box.
1. The history of ________ goes back to about 8 000 B.C. when people first used an ax as a woodworking ________. 2. Hardwoods have beautiful _______ and can be used to make furniture. 3. Woodworking use a wide variety of ________
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to ________ wood and to bring out the beauty of the grain. 4. Wood swells if
placed in _______ atmosphere. 5. Hardwood or softwood can be used to make ________. 6. Plywood consists of an ________ number of thin _______ of wood glued together. 7. Different _________ spoil the appearance of wood without affecting ________ properties. 8. Experience of many decades has shown the ________ and _______ of wood as compared with other ________.