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3. Look through the text (exercise 2) and choose the correct answer.
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3. Look through the text (exercise 2) and choose the correct answer.
1. Which of these is the smallest particle?
a) An atom
b) A molecule
c) A compound
2. Which of these is the correct symbol for magnesium?
a) MG
b) mg
c) Mg
3. Which statement about atoms and molecules is correct?
a) Elements always exist as separate atoms.
b) Elements always exist as pairs of atoms called molecules.
c) Elements and compounds can exist as molecules.
4. How many different atoms are there in a compound?
a) One
b) Always two
c) Two or more
5. Approximately how many elements are there?
a) 100
b) 4
c) 1, 000, 000
6. Which one is a compound?
a) Water
b) Hydrogen
c) Helium
7. Which of these contains two carbon atoms and six hydrogen atoms?
a) CH4
b) C2H6
c) C2H4
8. Which of these contains four hydrogen atoms?
a) CH3OH
b) H2O
c) H2O2
9. How many atoms are there in total in a molecule of sulfur trioxide, SO3?
a) Two
b) Three
c) Four
10. Why does air not have a definite formula?
a) It contains different amounts of water depending on where you are.
b) It depends on the temperature.
c) It is not a compound.
(from: http: //www. bbc. co. uk/education/guides/zt2hpv4/test)
4. Match the word with the correct definition.
| 1. Atom 2. Element 3. Molecule 4. Compound | a) A substance formed by the chemical union of two or more elements. b) A collection of two or more atoms held together by chemical bonds. c) A substance made of one type of atoms only. d) The smallest part of a substance that can exist. |
PART 2. ELEMENTS IN THE EARTH'S CRUST
5. Read and learn the following words.
| 1. oxygen – кислород 2. hydrogen – водород 3. carbon – углерод 4. carbonic acid gas (carbon dioxide) – углекислый газ 5. odour – запах 6. taste – вкус 7. weight - вес 8. solid – твердый 9. liquid – жидкий 10. gaseous – газообразный 11. transparent – прозрачный 12. flammable – горючий, легко воспламеняющийся 13. soluble - растворимый 14. to spread (spread, spread) – распространяться 15. abundant – часто встречающийся, широко распространённый 16. earth – земля 17. crust – кора 18. rock – горная порода 19. to constitute – составлять 20. constituent – компонент, элемент, составляющая | 21. condition – условие 22. pressure – давление 23. stable – устойчивый, стабильный 24. to occur – встречаться, случаться 25. quantity – количество 26. state – состояние 27. compound – смесь, соединение 28. formation – образование, формирование 29. destruction - разрушение 30. lithosphere – литосфера, земная кора 31. to increase – увеличивать(ся), возрастать 32. to compare – сравнивать 33. to reach – достигать 34. stratum (pl. strata) – пласт, слой 35. content – содержание, доля 36. enormous – огромный 37. deep – глубокий 38. earth’s interior – недра земли |
6. Read the text and translate it into Russian.
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Elements in the Earth's Crust
A chemical element is a pure chemical substance consisting of a single type of atoms. When two or more distinct elements are chemically combined, with the atoms held together by chemical bonds, the result is termed a chemical compound. Although two thirds of the chemical elements occur naturally on the Earth only as compounds some occur as native elements, for example gold, silver, copper and carbon.
Even though there are over 100 elements that are naturally found, only eight of them are common in the rocks that make up the Earth’s outer layer, the crust. Together, these eight elements make up more than 98 % of the crust. The eight most common elements in Earth’s crust (by mass) are oxygen (47%), silicon (28%), aluminum (8%), iron (5%), calcium (4%), sodium (3%), potassium (2%), and magnesium (2%).
Oxygen is the most abundant element in the earth's crust. Scientists estimate oxygen comprises nearly half of the mass of the crust. It also accounts for 21 percent of Earth's atmosphere. Oxygen is a gas that is colorless, odorless, and tasteless, slightly soluble in water and slightly heavier than air. Oxygen is a highly reactive element capable of combining with most other elements. For example, oxygen and iron (Fe) form various compounds we know as iron ore. In combination with hydrogen and carbon oxygen forms the widely spread compounds – water and carbonic acid gas. Both these combinations are highly active agents in the formation and destruction of minerals.
As the second most abundant element in the Earth's crust, silicon accounts for about 28 percent of its mass. Combined with oxygen, silicon dioxide is the most common compound in the crust. Most people know silicon dioxide as common sand, but it can also take the form of quartz and other crystalline rocks.
Aluminium is the third most common element in the Earth's crust. Aluminium is the crust's most abundant metal, but all the earth's aluminium has combined with other elements to form compounds, so it is never found free in nature. Aluminium oxide is a common aluminium compound.
Iron is one of the most common and cheapest of all metals and accounts for over 5 percent of the Earth's crust, making it fourth on the list of abundant elements. Iron combined with carbon makes steel.
The Earth's crust contains calcium, sodium, magnesium, and potassium in abundance. These elements are never found free in nature due to their high reactivity.
(from: http: //www. ehow. com/info_8120554_eight-abundant-elements-earths-crust. html, http: //www. windows2universe. org/earth/geology/crust_elements. html)
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