PROPERTIES OF CHEMICAL REACTIONS

 

An atom is the smallest particle of an element that can retain the chemical properties of that element. It is composed of a nucleus, which contains positively charged protons and neutral neurons, around which negatively charged electrons revolve in orbits. For example, a helium atom contains 2 protons, 2 neurons, and 2 electrons.

An ion is a positively or negatively charged atom or group of atoms. An ion which is negatively charged is called an anion, and a positively charged ion is called a cation.

Isotopes are alternate forms of the same chemical element. A chemical element is defined in terms of its atomic number, which is the number of protons in its nucleus. Isotopes of an element have the same number of protons as that element, but a different number of neurons. Since atomic mass is determined by the number of protons plus neurons, isotopes of the same element have varying atomic masses.

All substances are composed of matter, they have mass and occupy space. Elements and compounds constitute two general classes of matter. Elements are substances that consist of identical atoms (i.e., atoms with identical atomic numbers). This definition of an element includes all isotopes of that element. Hence O¹⁸ and O¹⁶ are both considered to be elemental oxygen. A compound is a substance that is composed of two or more different kinds of atoms (two or more different elements) combined in a definite weight ratio. This fixed composition of various elements, according to law of definite proportions, differentiates a compound from a mixture. Elements are the substituents of compounds. For example, water is a compound composed of the two elements hydrogen and oxygen in the ratio 2: 1, respectively. This compound may be written as H₂O, which is the molecular formula of water. The subscript “2” that appears after the hydrogen (H) indicates that in every molecule of water there are two hydrogen atoms. There is no subscript after the oxygen (O) in the molecular formula of water, which indicates that there is only one oxygen atom per molecule of water. Hence water is a compound whose molecules are each made up of two hydrogen atoms and one oxygen atom.

 

POST-READING TASKS

Define the following terms: atom, isotope, ion, element, compound.

Describe the differences between an element and a compound.

Talk about different constituents of matter.

 

GRAMMAR EXERCISES

Ex. 1. Choose between the Present Simple (Indefinite) and Present Continuous (Progressive) tense-forms.

 

1. They usually sit/are sitting for hours without saying a word.

2. She is keeping/keeps her room tidy as a rule.

3. Next week we sign/are signing the contract.

4. Could you turn off the television? Nobody watches/is watching it now.

5. Water doesn't exist/isn't existing on the Moon.

6. Don’t ask me what spinach is tasting/tastes like. I’ve never tried it.

7. Ann is applying/applies this ointment every other day.

8. We are seeing/see each only occasionally.

9. How do you get/are you getting to your office?

10. The water in this lake seldom is freezing/freezes in winter.

Ex. 2. Open the brackets using the Present Simple or the Present Continuous tense-forms.

 

1. My wife has never been to France. She (plan) to go there next summer.

2. You (understand) what he (talk) about?

3. What you (do) tomorrow evening? — I (go) to the theatre.

4. I usually (not/have) breakfast before I (go) to work.

5. What a beautiful dress you (wear/. When did you buy it?

6. Jane (be) in Paris now. She (learn) French there.

7. You (hear) this noise downstairs? What can it be?

8. Excuse me, but you (stand) on my foot.

9. You always (complain) about the weather!

10. Have you got a light? – Sorry, I (not smoke).

11. Students often (think) that exams (be) a nuisance.

12. Nancy (look) like her father.

13. Peter seldom (tell) the truth. You can’t believe everything he (say).

14. Your car is so clean. How often you (wash) it?

15. What you (do)? – I’m an engineer.

16. The soup (taste) good.

17. Your brother (be) a student now! – Yes, he (study) at university.

18. Ann (play) the piano better than Susan. And who (play) now? – I (think) it (be) Susan.

19. She (be) a dietician. She (help) people to choose the right food.

20. They (say) if you (see) a black cat, you (not have) good luck.

21. She (give) two concerts in London next week.

22. What time the children (come) out of school, as a rule?

23. Why you (smell) the meat? It (not/be) fresh?

24. You (believe) in God?

25. She (be) still ill but she (get) better now.

26. It often (rain) here at this time of the year?

27. What he (do)? – He (try) to get the car started.

28. Where you (come) from? – I (come) from Russia.

29. What he (mean) by saying this? It (sound) strange.

30. She always (be late) for classes!

31. This carpet (cost) 30 dollars. Why not buy it?

32. Believe me, I (think) about you all the time.

33. I (not/know) how (make) both ends meet. They (have) six children and (not/earn) very much.

34. My mother (think) that hitch-hiking (be) very dangerous.

35. People (like) stability in life.

36. They (open) a new McDonald’s tomorrow.

37. What a wonderful day we (have) today!

38. When snakes (lose) their skins?

39. My brother (not/care) very much what he (look) like.

40. She always (lose) her temper!

 

Ex. 3. Ask your groupmates:

1. When they get up in the morning.

2. What subjects they study.

3. Haw many tutorials they will have tomorrow.

4. What languages Maria studies.

5. Whey they study.

6. What language they speak at the English lessons.

7. Why Olga gets up so early.

8. Where his father works.

9. Whom they write letters to every Sunday.

10. Whose pictures they like best.

11. Who is absent today.

 

Ex. 4. Change the following statements to questions beginning with the question – words given in brackets.

1. He lives in Vitebsk. (where? )

2. I study at Byelorussian State University. (where? )

3. He has 20 English books. (how many? )

4. They get up at 7 o’clock in the morning. (when? )

5. Maria does her morning exercises every day. (who? )

6. They play tennis very well. (how? )

7. She goes to University every day. (where? )

8. Classes begin at 8.30. (when? )

9. Ann speaks English well. (who? )

10. They study English. (what language? )

11. We have two English classes a week. (how many? )

12. The students often come home late. (who? )

13. We study many interesting subjects. (what? )

 

Ex. 5. Put all kinds of questions to the following sentences and make them negative.

 

1. The academic year begins in December.

2. They speak English well.

3. My friend lives in the hostel.

4. I go to bed at 11 o’clock.

5. He reads newspapers every day.

6. I do my homework in the reading-room.

7. She wants to play tennis.

8. They study physics.

 

Ex. 6. Which of the underlined verbs is right? The information is about the USA.

1. Most shops usually open/opens at 8.30 a.m. and close/ closes at 6.00 p.m.

2. The banks doesn't/don't usually close at lunchtime.

3. Many children has /have a computer at home.

4. The New York subway usually works/work very well.

5. It doesn't/don't often snow in California.

6. Most people don't/doesn't work on Sundays.

7. The capital city, Washington, have/has a population of about one million.

8. Many people in Los Angeles speak/speaks Spanish.

9. Schoolchildren don't/doesn't usually wear uniform.

 

Ex. 7. Ten sentences are wrong and two sentences are right. Correct the mistakes where necessary.

 

1. David never take the bus to work.

2. Go you to the office every day?

3. My car don't work when it is cold.

4. What time the film starts?

5. Ben's sister don't speak French but Ben do.

6. How many eggs you want for breakfast?

7. Does the 9.30 train stop at every station?

8. What does do your father?

9. I not write many letters. I usually use the telephone.

10. What Sue usually have for lunch?

11. How much do these apples cost?

12. Charlie plays basketball but he doesn't enjoys it.

 

Ex. 8. Present continuous or present simple? Complete the sentences choosing the right verb form.

1. … learning English? (Do you like / Are you liking)

2.... this programme. (I'm not understanding / I don't understand)

3. Jim and his father.... They are asleep. (aren't watching / don't watch TV)

4. Tony is upstairs in the bathroom. He... his hair. (washes / is washing)

5. Why...? Are we late? (do we run / are we running)

6. There are some strange noises in the sitting room. What...? (is Tom doing / does Tom do)

7. What time... every day? (does John get up / is John getting up)

8. Fred and I are good dancers but we... to discos very often. (don't go / aren't going)

9. A: ... from Denmark? B: No, I'm Swedish. (Are you coming / Do you come)

10. … in the same hotel in New York. (I always stay / I'm always staying)

11.... in winter in your country? (Does it snow / Is it snowing)

12. Joanna... the dinner at the moment. (isn't cooking / doesn't cook)

13. She... on the phone, (talks / s talking)

 

Ex. 9. Complete the sentences. Put the verbs into the present simple (e.g. do) or present continuous (e.g. I'm doing), positive or negative.

 

1. A: Have a chocolate. В: No thank you. I … (like chocolate)

2. A: Let's have lunch in the garden. В: No, we can't. It’s … (rain)

3. A: What...? B: Pam? She's a doctor. (do)

4. Tony... at the moment. He's on holiday. (work)

5. A: Why...? B: Because I'm happy. (smile)

6. Sandra and her husband are vegetarian. They... (eat meat)

7. A: What...? B: A letter from my sister. (read)

8. A: What time...? В: Me? About 7.00 a.m. usually. (get up)

9. A: Where's Dave? B: He's in the kitchen. He....(make coffee)

10. A: How...? B: I usually catch a bus. (go to work)

11. A: I think Shaun and David are asleep. B: Mmm. Turn the TV off. They... (watch it)

12. John and I want to go to Greece for our holidays, so we.... (learn Greek)

 

UNIT 2

 

GRAMMAR: PAST SIMPLE. PAST CONTINUOUS.

TEXTS: THE CELL. CELLS

 

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