THE ELEMENTS – SYMBOLS, FORMULAS AND EQUATIONS Chemical SYMBOLS are a short way of writing ELEMENTS. E.g. H (hydrogen), N (nitrogen) Chemical FORMULAS are a short way of writing COMPOUNDS. E.g. NaCl (sodium chloride) Note that for English names of inorganic compounds, the order of the electronegative and the electropositive element is different than in Czech. E.g. NaCl - Cz : chlorid sodný, En : sodium chloride Here are some common compounds, their names and formulas. NaCl – sodium chloride H[2]SO[4] – sulphuric acid ZnSO[4] – zinc sulphate C[6]H[6 ] - benzene ZnO – zinc oxide HCl – hydrochloric acid Na[2]CO[3] – sodium carbonate NH[3] - ammonia CO[2 ] - carbon dioxide NaOH – sodium hydroxide These formulas are useful for writing EQUATIONS. [] Equations are a short way of expressing chemical reactions and their results. E.g. HCl + NaOH → NaCl + H[2]O We read as: hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water. 1. Try and complete these equations: 1. CuO + H[2 ]→ ……………………………… (copper oxide reacts with hydrogen to form copper and water) 2. Na[2]CO[3] + 2 HCl → ………………………….. (sodium carbonate reacts with hydrochloric acid to form sodium chloride, carbon dioxide and water) 3. Zn + 2HCl → …………………………… (zinc reacts with hydrochloric acid to form zinc chloride and hydrogen) 2. Express these equations in words: 1. 2 Na + Cl[2 ]→ 2 NaCl 2. ZnO + H[2]SO[4 ]→ 2 ZnSO[4] + H[2]O 3. 2 Na + 2 H[2]O → 2 NaOH + H[2] THE ELEMENTS - COMPARING 1. Discuss the following issues: · How often do we use comparing and contrasting in everyday life? Try to recall what you have compared today. · Why do we compare things? What is it good for? · How do you compare? · Give some examples from your chemistry classes. 2. Read the following passage and find as many comparisons as you can. The Wonder Metals 1 The study of metals began in the Middle Ages when alchemists searched for a technique to convert “base metals”, like lead, to gold. They never succeeded in making gold but at least by experimenting with the metals (in contrast to the ancient Greeks, who only speculated about them) they made discoveries. 5 10 All but 20 of the over 100 elements identified to date are metals but only 7 of these are common in the earth´s crust. Iron, the most widely used metal, is rarely found in the free state (not combined with other metals) and must be extracted from naturally occurring compounds (ores) such as hematite, magnetite, and pyrite. The beautiful colors of rocks are due almost entirely to these iron compounds. In fact, iron pyrite is often called fool´s gold because of the similarity of its color to gold. Iron is very strongly magnetic, and the fact that the earth is a magnet itself tipped scientists off to the fact that iron is a major component of the earth´s core, or centre. 15 Pure iron is a relatively soft, silvery metal that is very active chemically (that is, it combines with oxygen to corrode or form rust). It is usually mixed with other elements or compound to form alloys such as steel, stainless steel, or cast iron, which are more durable and rust resistant than pure iron. 20 Aluminum is the most abundant metal, but it was not used until a century ago because it is so active chemically and difficult to extract. Like iron it is soft, but in contrast to iron and steel, aluminum is very light and more resistant to corrosion. These qualities make it useful for airplanes, trains, automobiles, rockets, and house siding. In the 1940s, magnesium emerged as an important metal. Although it is less abundant in the earth, more chemically active, and harder to extract than aluminum, it is present in sea water and that means there is almost an endless supply of it. 25 In the space age, the extraordinary properties of titanium have made it the new wonder metal. Lighter and stronger than steel, it is more resistant to corrosion and able to withstand heat. The remaining major metals are sodium, potassium, and calcium, all too active chemically (they react violently with water) for use in construction. 3. Can you give some more examples of comparing words? Comparing similarities Magnesium is like as important as similar to comparable to aluminum. Both carbon dioxide and hydrogen are gases. Carbon dioxide and hydrogen are both gases. Magnesium resembles parallels aluminum in many ways. Contrasting differences Iron is unlike is different from differs from aluminum. Unlike iron, In contrast to iron, Compared to iron, In comparison to iron, aluminum is light. Iron is heavy, whereas aluminum is light. Carbon is an element, while/whilst carbon dioxide is a compound. Although/even though/though copper and aluminum are both good conductors, aluminum is used in aviation because it is far lighter. Iron is a relatively comparatively soft metal. Iron is (far/much) heavier than less abundant than not as soft as aluminum. Adjectives – comparing 2. stupeň (comparative) light → lighter lehký → lehčí a) koncovka –er: jednoslabičná přídavná jména a dvouslabičná přídavná jména končící na –y po souhlásce (light → lighter, y→ier: heavy→heavier) b) pomocí výrazu more:všechna ostatní přídavná jména a také příslovce, která končí na –ly. (abundant → more abundant, heavily → more heavily) c) nepravidelné tvary: good/well→better, bad/badly→worse, far→further (nebo farther) little→less, old → older/elder (elder brother – o členech rodiny) - před druhým stupněm lze použít následující výrazy: far (= a lot), much, a lot, a bit, a little, slightly (= a little); e.g. much heavier – mnohem těžší 3. stupeň (superlative) the lightest nejlehčí a) light → lighter → the lightest, heavy → heavier →the heaviest b) abundant → more abundant → the most abundant c) good → the best, bad → the worst, far → the furthest, little → the least, old → the eldest 4. Use the right comparative or superlative Iron is ……………………………. (abundant) than silver. (comparative) Lead is much …………………..… (heavy) than aluminium. (comparative) Radium disintegrates far………………………… (quickly) than tin. (comparative) Platinum is ……………………………. (expensive) metal. (superlative) Litihium is …………………………….. (light) metal. (superlative) 5. Listen to these statements about three metals: iron, aluminium and lead. Complete the chart. IRON ALUMINIUM LEAD Density Does it corrode? Is it easy to extract? Now write 3 sentences, comparing these metals. E.g. In contrast to iron, aluminium doesn´t corrode. 6. Tables, charts, and graphs are useful for organizing information. Circle the answer that best completes the statement according to the information in the chart. The Physical Properties of Six Metals Metal Specific Gravity Melting Point (°C) Boiling Point (°C) Atomic Radius (Å) Ionic Radius (Å) Group I Copper Silver Gold 8.9 10.5 19.3 1083 960 1063 2595 2212 2966 1.17 1.34 1.34 .96 1.26 1.37 Group II Zinc Cadmium Mercury 7.14 8.65 13.60 420 321 -38.87 907 765 357 1.25 1.41 1.44 .74 .96 1.1 1. The atomic radius of cadmium is …………………… that of mercury. a. as high as b. not as high as 2. ……………………….. mercury, cadmium has a high boiling point. a. Like b. Compared to 3. The specific gravity of cadmium and copper are ……………………………. . a. similar b. identical 4. Compared to the other metals in this table, gold has ………………… specific gravity. a. a relatively high b. the highest 5. The properties of cadmium and zinc are …………………… . a. comparable b. identical 6. Copper and gold have ……………………. high boiling points. a. comparatively b. equally 7. The melting points of the Group II metals are …………………. those of Group I. a. lower than b. as low as 8. The ionic radius of copper is …………………….. to that of cadmium. a. similar b. equal 7. Read the text and then order the seven metals according to their melting points. List the metal with the highest melting point first. The melting point of platinum is high compared to most metals but not as high as that of chromium. The melting point of zinc is less than half the melting point of gold and approximately three times the melting point of sodium. Mercury has the lowest melting point of all the metals. Copper and gold have similar melting points, but the melting point of copper is slightly higher than gold and lower than platinum. 8. Work in small groups. Write a short text, comparing two items of your choice. 9. HOMEWORK FUTURE - BUDOUCNOST FUTURE SIMPLE will/shall+ infinitiv Tento tvar se používá pro vyjádření prostého děje děje budoucího, např.když se o činnosti rozhodneme v momentě mluvení: · What would you like to drink? – I´ll have an orange juice, please. nebo když předvídáme, co se stane - s výrazy probably, I expect, I´m sure, I think · Do you think Ann will pass the exam? – Yes, I´m sure she will pass easily. nebo když nabízím, že něco budu dělat/ žádám někoho, aby něco udělal: · That bag is too heavy. I´ll help you with it. / Will you shut the door, please? Shall se běžně pro vyjádření budoucnosti v hovoru nepoužívá, je to spíše tvar objevující se v psaném projevu. Dnes se spíše objevuje ve významu „Mám to udělat?“ nebo ptám-li se na něčí názor nebo dávám-li návrh. · Shall I close the door? · I have no money. What shall I do? · Where shall we go this evening? FUTURE CONTINUOUS Průběhový tvar will be ....ing se použije, chceme-li vyjádřit že v určitou dobu nebo po určitou dobu v budoucnosti: · Don´t phone between 7 and 8. We will be having dinner then. · This time next week I´ll be lying on a beach. JINÉ ČASY K VYJÁDŘENÍ BUDOUCNOSTI Přítomný čas prostý (present simple) se používá k vyjádření budoucnosti, když je řeč o jízdních řádech, programech kin, televize, atd.: · The train leaves at 10:00 and arrives at 12:30. · What time does the film begin? Jinak mluvíme-li o činnostech, které jsme si zařídili, o kterých víme, že je budeme v budoucnu dělat, používáme průběhový tvar přítomného času (present continuous) · What are you doing on Saturday evening? – I´m going to the theatre. · I´m not working tomorrow, so we can go somewhere. V těchto větách lze použít i konstrukci be going to (What are you going to do on Saturday evening? – Co hodláš dělat... ), ale přítomný čas průběhový je tu přirozenější. Rozdíl mezi použitím průběhového tvaru a konstrukce be going to je následující: Použitím průběhového tvaru spíše naznačím, že je něco už zařízeno, domluveno, použitím konstrukce be going to spíše naznačím, že jsem se rozhodla něco udělat, mám to v úmyslu, ale nemusím to mít zařízeno. · I´m leaving tomorrow, I´ve got my plane tickets. · The windows are dirty – Yes, I know, I´m going to clean them later. Další použití be going to: v případech, kdy říkáme, že se něco stane, protože situace to mu nasvědčuje: · The man can´t see where he´s walking. There´s a hole in fornt of him. He´s going to fall into the hole. · Look at those black clouds. It´s going to rain. CVIČENÍ Dejte sloveso do tvaru přítomného času prostého nebo průběhového. 1) I´m going (go) to the theatre this evening. 2) Does the film begin (the film / begin) at 3:30 or 4:00? 3) We............................... (have) a party next Saturday. Would you like to come? 4) The art exhibition ............................(open) on 3 May and ...........................(finish) on 15 July. 5) I ...........................................(not / go) to a concert tonight. It ..................................(begin) at 7:30. 6) You are on a train to London and you ask another passanger: Excuse me, what time ...........................(this train / get) to London? 7) You are talking to Ann: Ann, I .................(go) to town. ..................(you / come) with me? CVIČENÍ 1) Odpovězte na otázky. Všechny ty věci se chystáte udělat, ale ještě jste je neudělali 2) Have you cleaned the car? – (tomorrow) Not yet, I´m going to clean it tomorrow. 3) Have you phoned Sally? – (later) Not yet. ................................. 4) Have you done the shopping? – (this afternoon) Not yet. ......................... 5) Have you read the paper? – (after dinner) Not yet. .............................. CVIČENÍ Co se nejspíš v těchto situacích stane? Použijte slov v závorkách 1) There are a lot of black clouds in the sky. (rain) It´s going to rain. 2) It is 8:30. Jack is leaving the house. He has to be at work at 8:45, but the journey takes 30 minutes. (late) He ............................. 3) There is a hole in the bottom of the boat. A lot of water is coming in trough the hole. (sink) The boat ................ CVIČENÍ Který výraz je správný? 1) Did you phone Ruth? – Oh, no, I forgot. [DEL: I phone :DEL] / I´ll phone her now. 2) I can´t meet you tomorrow afternoon. I´m playing / I play atennis. 3) I meet / I´ll meet you outside the hotel in half an hour, OK? – Yes, that´s fine. 4) Remember to buy a newspaper when you go out. – OK, I don´ t forget, / I won´t forget. 5) What time does your train leave / will your train leave tomorrow? 6) I don´t want to go out alone. Do you come / Will you come with me? 7) It´s a secret between us. I promise I don´t tell / I won´t tell anybody. CVIČENÍ Který tvar je správnější nebo běžnější? 1) Ann isn´t free on Saturday. [DEL: She´ll work :DEL] / She´s working. 2) I´ll go / I´m going to a party tomorrow night. Would you like to come too? 3) I think Jane will get / is getting the job. She has a lot of experience. 4) I can´t meet you this evening. A friend of mine will come / is coming to see me. 5) There´s no need to afraid of the dog. It won´t hurt / it isn´t hurting you. 6) Tomorrow at this time I will eat/ will be eating spaghetti. 7) Look at the clouds. It will/is going to snow.