- •Unit 5. Covalent Bonds
- •1. Fill in the table:
- •3. Read the dialogue and learn how to speak about your past activities. Put the verb in brackets into the Past Continuous. Pay attention to the terms of electricity.
- •4. Put in the missing words, using the words from the table above:
- •5. Put all possible questions to the following statements.
- •6. Put the verb in brackets into the Past Continuous:
- •7. Form nouns from the following verbs using the suffix ‘-ment’ and translate them:
- •8. Choose the appropriate English equivalents.
- •9. Translate the text. Use a dictionary if necessary. To each sentence put different type of question in Present Continuous.
- •10. Read and Translate word-combinations starting from the first component:
- •11. Match the following word-combinations with their translation:
- •12. Match the following sentences with their translation:
- •13. Choose as many words as you can of Ex.1 and form sensible sentences.
- •Specialist Reading.
- •14. Read the text ‘Covalent Bonds’ only once. How much can you remember? Answer these questions without additional reading.
- •If you failed try to answer these questions again after doing the exercises given below the text.
- •15. Read the text again and complete the sentences with the correct ending.
- •16. Study the text and translate the following:
- •17. Match the terms in Table a with their definitions in Table b.
- •Speaking.
- •18. Summarize the text ‘Covalent Bonds’ in 150 words.
- •19. In pairs ask and answer text-based questions.
- •20. Divide into 2 groups. Group 1 translates Extract a and group 2 – extract b of the text “Semiconductors” with a dictionary in writing.
16. Study the text and translate the following:
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все элементы сгруппированы по их химическим свойствам
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элементы со схожими свойствами
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некоторые из элементов существуют в больших количествах
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некоторые элементы вообще не существуют в природе
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некоторые элементы создаются физиками-атомщиками
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специальное оборудование
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валентные электроны
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электроны внешней оболочки атома
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твёрдый кусок чистого кремния
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каждый валентный электрон вращается вокруг исходного атома
17. Match the terms in Table a with their definitions in Table b.
Table A
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concentration
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absorption
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equipment
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impurity
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resistance
Table B
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A process in which something takes in liquid, gas, or heat.
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The ability of a substance to stop the flow of an electric current through it.
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The amount of a substance contained in a liquid.
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The tools, machines, clothes etc that you need to do a particular job or activity.
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A substance of a low quality that is contained in or mixed with something else, making it less pure.
Speaking.
18. Summarize the text ‘Covalent Bonds’ in 150 words.
19. In pairs ask and answer text-based questions.
For example:
- How many elements are known to science today?
- Do you know that some elements do not exist at all in nature?
- How can we define valence electrons?
- And what if we consider atoms in a solid piece of pure silicon?
20. Divide into 2 groups. Group 1 translates Extract a and group 2 – extract b of the text “Semiconductors” with a dictionary in writing.
EXTRACT A.
The two semiconductor materials used in the manufacture of semiconductor devices, such as diodes and transistors, are germanium and silicon. Both these materials fall into group IV of the Periodic Table of Elements. An atom of either substance may be represented by a central core having a positive charge and surrounded by orbiting electrons, each having a negative charge.
In its solid state silicon forms crystals of the diamond type, i.e. it forms a cubic lattice in which all the atoms except those at the surface are equidistant from their immediately neighbouring atoms. A study of crystal structure shows that the greatest number of atoms that can be neighbours to a particular atom at an equal distance away from that atom and yet be equidistant from one another is four. Hence each atom in a silicon crystal has four neighbouring atoms. In the crystal lattice each atom employs its four valence electrons to form covalent bonds with its four neighbouring atoms; each bond consists of two electrons, one from each atom. Each pair of electrons orbits around both its parent atom and a neighbouring atom.
EXTRACT B.
Semiconductors are soilids whose resistivity lies between those of electrical conductors and insulators. Semiconductors are used in computers, in radio and TV receivers, and in other electronic products.
Semiconductor devices perform many control functions. They may be used as rectifiers, amplifiers, detectors, oscillators and switching elements. Some characteristics, which make the semiconductors such an attractive member of the electronics family are the following:
1. Semiconductors are small and light in weight.
2. Semiconductors are solids. There is therefore little chance that elements will vibrate. Element vibration in vacuum tubes was the cause of microphonics.
3. Semiconductors require little power and radiate less heat than tubes. They do not need warm up time and operate as soon as power is applied.
4. Semiconductors do not undergo the chemical deterioration which occurs in tube cathodes. The deterioration of tube cathodes eventually results in unacceptable tube performance.
Silicon is the material of which most semiconductor devices are presently constructed.
21. In Russian write a content-based summary of the text you have translated.
22. Translate into English the summary made in ex.20 of the text you haven’t read.
23. Make a reverse written translation (from Russian into English) of the Extract you have translated.
24. Serve as simultaneous interpreter. Make an oral reverse interpretation of the text.
25. Find more information about semiconductors and tell your group mates.