Home Random Page





27 Recrystallization is just one of a number of separation methods and processes. Choose one of those listed below and search the Internet for information. Then write 5 key words on the board and do a mini-presentation on your findings to the class, giving the most important details (what the method or process is based on, how it works, where it is used).


Adsorption, centrifugation, chromatography, decantation, distillation, drying, electrophoresis, extraction, flocculation, filtration, magnetic separation, precipitation, recrystallization, sieving, stripping, zone melting (also called zone refining).





28 Go back to Unit 2 ex. 21 and look at the underlined words in the text. What is their role? Assign the words to the relationship categories shown in the table below:



Relationship Linking word or expression
Addition and, in addition, moreover, also, as well  
Contrast despite, in spite of, in contrast, while, nevertheless, on the one hand……on the other hand, not only……but also  
Reason as, due to, because of  
Purpose in order to, so as to, with the aim of  
Result so, as a result  
Condition unless, otherwise, as long as  
Similarity similarly  
Summary on the whole, on balance  


29 What are the rules? Choose the correct options.


In formal writing, so/therefore is used to connect ideas within one sentence, while so/therefore can be used in a single sentence or to connect two sentences.
Sentences do not usually begin with therefore/but in written English.

You should not use in addition/and to start a sentence when you are writing a scientific paper.

Although most linkers are followed by a verb clause, because of, despite and in spite of /because, although and however are followed by a noun or an –ing form.



30 Choose the best alternatives to complete the “teenager’s kitchen experiment”.


If/Because you put an egg in a container with vinegar, the egg shell will soften and, after certain time, disappear. The explanation is as follows.

Egg shells are quite hard because/because of they contain calcium carbonate. But/However, vinegar contains C2H4O2; due to/because that, the acid reacts with the calcium carbonate, and/in addition carbon dioxide is released, forming bubbles in the vinegar. The chemical reaction continues until all the carbon is used up. It is not a very fast process because/therefore C2H4O2 is a weak acid. Nevertheless/In contrast, after a day or two the shell dissolves completely. The egg is then soft as/so as to all of the carbon floated out of the egg in those little bubbles.

Once/Despite you take the egg out of the container and leave it exposed to air, a reverse reaction will start. The calcium remaining in the egg shell will bond with the carbon from the carbon dioxide in the air. In order to/As a result, the egg becomes hard again.

Similarly/On balance, you can experiment with e.g. chicken bones. Immerse them in vinegar in order to/whereas make them soft. Consequently/But, you will be able to bend them, make different shapes of them, or even tie them in a knot. Take them to school so that/although your friends can share the amusement. Unfortunately/Accordingly, there is no guarantee that the bones experiment will improve your chemistry school mark, but at least it will be fun.



31 Look at the sentences in ex. 30 and decide wheather the following punctuation statements are true of false.


Words connecting two sentences (e.g. Similarly, In addition, etc.) are usually followed by a comma.

There is never a comma before and.

Except for inserted clauses, there is usually no comma before if.

Usually there is no comma before because.

Usually there is no comma before but.


32 Transform the sentences, using the words given.


The shell disolved because the liquid was acidic.

(because of)



Although we have run the separation process several times, we have not been able to obtain a pure substance.





You must dilute the mixture, otherwise the concentration will be too strong.


(in order to)





33 Before listening, discuss the following questions:

· Do you use any plasticware in your laboratory?

· Do you expect plasticware to be affected by chemicals more easily than glassware?


34 Listen to the recording and decide whether these statements are true (T) or false (F). Correct the false ones.


a. The scientists expected the influence of ammonium chloride concentration in reaction with an enzyme linked to Parkinson’s desease.

b. This influence has been confirmed.

c. The scientists found several chemicals that came out of the polypropylene containers.

d. Di HEMDA is used to stop anything growing in the container.

e. Oleamide has similar usage as Di HEMDA.

f. These experiments prooved plasticware not to be generally suitable for laboratory work.

g. Plasticware will not be used in laboratories in future.


35 Listen again; this time follow the transcription of the interview and fill in the missing words.


Interviewer - Chris Smith

Now to a way in which our experiments could be thrown into disarray, Matt tell us about this.

Interviewee - Matt Wilkinson

Yes, a team of Canadian ………………….. led by Andrew Holt at the University of Alberta have shown how chemicals leaching from plasticware can actually ………………….. the reactions that you do in them dramatically.

Interviewer - Chris Smith

So what were they doing? How did they find it?

Interviewee - Matt Wilkinson

Well, they were initially studying how an enzyme linked to Parkinson's disease, reacted with ammonium chloride, and surprisingly they found that it didn't seem to ………………….., how much they diluted that ammonium chloride, the ………………….. were still there.

Interviewer - Chris Smith

So something was amiss. How did they try to find out what it really was?

Interviewee - Matt Wilkinson

What they did was that they started off by seeing if they could extract anything from the ………………….. themselves and they found that there were two chemicals in particular that came out of the polypropylene containers, while they were doing these reactions that seemed to inhibit the enzyme. One of these is the disinfectant DiHEMDA, which is used to stop anything growing in the containers, while they're in ………………….. and the other is the lubricant, oleamide, that's used to stop the packages from sticking together during the ………………….. process.

Interviewer - Chris Smith

So where were these chemicals coming from? Were they actually in the plastic itself?

Interviewee - Matt Wilkinson

They're actually in the plastic themselves.

Interviewer - Chris Smith

And do we know how they were interfering with the chemical reaction that the researchers were trying to …………………..?

Interviewee - Matt Wilkinson

They've actually found that both of these chemicals are inhibitors of the enzyme itself.

Interviewer - Chris Smith

And this is obviously a bit of a canary in the cage, saying there are things in these plastic containers that could affect other reactions. Do they speculate as to how well this could throw a spanner in your scientific works?

Interviewee - Matt Wilkinson

Well, yes it kind of throws a spanner into any reaction that you're doing, that's ………………….. sensitive. If you're using any kind of plasticware from a container, through to a pipette, any plastic has the potential to leach some of its constituent chemicals out of it, the most interesting thing, I think, about this of course is that people have started using ………………….. plasticware to avoid the problems of incomplete cleaning of glassware.

Interviewer - Chris Smith

So, is this the death knell for laboratory plasticware then?

Interviewee - Matt Wilkinson

No, absolutely not, I think that it really emphasizes the need to run controlled experiments as we all should do anyway and you need to seriously control the plasticware that you do use, so that you can actually make sure that conditions are kept exactly the same.

Interviewer - Chris Smith

So maybe it's not always true the bad workman blame their ……... Thank you for that Matt.


36 Use the words you filled into the text in your own sentences



37 Compare the use of glassware and plasticware in the lab. Think of any pros and cons and draw a conclusion, using some of the linking words from the Text Building section (ex.28).




38 Work in small groups (3-4 people). Each group will be given a slip of paper with one word. Make a sentence which uses the word correctly, but instead of saying the word, say blip. If the other groups cannot guess the word, another member of your team makes another sentence with the same word.

Example: Water blip when heated to 100oC.




If you're not part of the solution, you're part of the precipitate!





Grammar File – Common Affixes and English Specific Infinitive Structures.





Ex. 24 Student B


Table B

Prefix Meaning Example Prefix Meaning Example
a-/an- without   milli-   millimetre
auto-   automation mono- one  
bi- two   multi-   multilevel
bio-   biology re- again  
co- together   semi-   semimetal
hydro-   hydrolysis tri- three  
kilo-   ultra-   ultraviolet
micro-   microscope un- not  



Date: 2015-01-12; view: 1037

<== previous page | next page ==>
doclecture.net - lectures - 2014-2021 year. Copyright infringement or personal data (0.004 sec.)