Английский. пособие Химики АЯ. Introduction

• Название: Introduction
• Анкор: Английский
• Дата: 20.09.2022
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2. Do you now how to describe an experiment? Read the description and complete the task.

Describing an Experiment

Beakers are filled with water, and into one a quantity of sugar is stirred. A quantity of sand is placed in the other and the liquid in both beakers is stirred vigorously. It will be, observed that the sugar seems to disappear completely, whereas the sand can still be seen clearly. No matter how vigorously or how long the sand is stirred in the water, it will not disappear, and when the stirring ceases the particles (or grains) of sand start to settle at the bottom of the beaker. In theory, no matter how long the liquid containing sugar is left standing, the sugar will not separate out from the liquid. Even if the sugar and water is left standing for a year or more, no sugar particles will be seen in the liquid. (This assumes that no evaporation of water takes place.) On the other hand, the sand will not dissolve in the water even if this beaker is heated while the mixture is being stirred.

Sugar

-water - sugar and water after vigorous stirring

sand

water- sand particles sand and water after vigorous stirring
From this demonstration, it can be seen that particles of sugar have dispersed throughout the water, and under normal conditions they will remain dispersed in this way. The sugar and water have formed a solution. However, despite vigorous stirring, the sand particles have failed to disperse in the same way. They have, remained completely separate and formed a suspension.

Now complete the account of what will happen if another experiment involving solutions is carried out. Complete the text with the correct form of the future tense of each verb.

Take some salt and stir it into some water in a beaker. It (dissolve) readily. Now do the same with some chalk. Very little (dissolve). It (observe) that chalk is less soluble than salt; chalk can be said to be relatively insoluble.

Continue to add salt to the salt solution, stirring continually. A point (reach) where the salt fails to dissolve. When no more salt (dissolve) in the water, the solution is said to be saturated. It (notice) that adding more salt (result in) the salt being deposited as a sediment at the'bottom of the beaker.

Consider what (happen) if a saturated solution is boiled. As the solution is heated, more salt (dissolve) until the boiling point is reached, and the solution is again saturated. Boiling (cause) the water to evaporate, and therefore the volume of the water (reduce). The salt, however, (remain) in the solution, so that the same amount of salt (be) present in a smaller volume of water. The smaller volume of water (not able) to hold all the salt in solution, so salt (begin) to appear as a solid. When a substance is deposited as a solid while a solution is being heated, it is said to crystallize out.
4. Very often it is necessary to use a variety of tenses when describing and discussing something, for example, when outlining the procedure for an experiment stating what will be observed. You will notice this in the following passage. Read the paragraphs carefully, and answer the questions which follow each one.

Add a quantity of copper sulphate crystals to some cold water Jn a beaker. Stir the water until all the crystals have dissolved. Continue to add crystals, still stirring the solution, until no more will dissolve and solid crystals are seen to float in the solution.

1. What has happened to the solution?

2. Why won't any more copper sulphate crystals dissolve?

3. What will happen if the stirring is stopped and the solution left to stand?

Now heat the solution gently. It will be noticed that the excess copper sulphate begins to dissolve. Continue heating gently until all the crystals have dissolved, and then begin to add more crystals. It should be possible to dissolve quite a lot more copper sulphate in the heated solution. Without letting the liquid boil, continue to dissolve copper sulphate in the solution until it has absorbed as much as possible.

4. What has this procedure demonstrated?

Now allow the solution to cool. As it cools, the solution will be less able to maintain such a high concentration, so that copper sulphate crystals will again begin to appear in the solution. The cooler the solution becomes, the more crystals will appear. When the solution has reached room temperature, there will be a quantity of solid crystals and the solution will be saturated.

5. Why will more crystals appear as the solution cools?

6. What will be the situation when the solution has reached loom temperature?
5. Complete the extract using the verbs in brackets in appropriate tenses.

Add a moderate quantity of salt to a beaker of water and stir the mixture vigorously until all the salt (dissolve). Continue to add salt, still stirring the solution until no more (dissolve) and a deposit of salt (observe) in the bottom of the beaker. Heat the solution (which is now saturated) gently. It (notice) that the excess salt begins to dissolve. Continue heating gently until all the salt (dissolve). Consider what (demonstrate) by this procedure. Now transfer the solution to an evaporating dish and heat it more strongly until it (boil). After a while it (observe) that the liquid level (reduce) as the water (evaporate), but at the same time salt (begin) to appear in solid form. Consider what (cause) salt to appear as the water (evaporate). Continue to boil the solution until all the water (evaporate).Attempt to deduce from the above discussion of solutions what will cause the solid salt to appear when a saturated solution of salt is boiled.
6 (a). The abbreviations and symbols below could all be used in a scientist’s lab notebook. In pairs, discuss what each one means. Match the abbreviations or symbols (1–12) to the correct meanings (a–l).

1. ∆	a) about; approximately
2. RT	b) at
3. ±	c) because
4. w/v	d) change
5. @	e) energy
6. .’ .	f) increases
7. . . ‘	g) leads to
8. →	h) more or less (to show the deviation from the number stated)
9. ↑	i) room temperature
10 E	j) therefore
11. w/	k) weight per volume
12.	l) with

6 (b). In pairs, decide how you might represent each of the following in a lab notebook. What other abbreviations do you often use in your lab notebook?

1. decreases	6. volume per volume
2. degrees Celsius	7. without
3. kelvin	8. two to one ratio
4. greater than or equal to	9. hours
5. positive	10. concentration

7. In pairs, discuss the following questions.

1. 
   What processes do you need to describe in your field of research? Who do you describe them for?
   
2. 
   How much detail do you need to include in your descriptions?
   
3. 
   What do you think are the most important points to remember when describing a process for other scientists?
   
4. 
   How do you keep a record of your experiments?
   
5. 
   Have you ever used a lab notebook software package?
   
6. 
   How does the lab notebook protocol in your current lab compare to other labs you have worked in?
   

8. A сhemistry student is summarising an experiment he has run. The language in the summary is grammatically correct, but the style is inappropriate. Read the three extracts (A–C) below. Then in pairs, first find examples of inappropriate style in the extracts. Then discuss what the student could do to improve the style of his report.

9. Vocabulary choice is very important to style. Below is a summary of another experimental procedure. For 1–10, underline the word or phrase which you think is in the most appropriate style for a formal scientific report.

In order to (1) determine / find out the value of n from (2) just one / a single experiment, (3) you should / it is necessary to have a range of stress levels actingwithin a (4) one thing / single specimen. (5) You can do this / This is achieved bymaking the sample into a coil. The stress (6) comes from / is provided by the weightof the coil itself, so that the upper part of the coil (7) experiences / gets more stressthan the lower parts. The stress in a particular turn of the coil is (8) proportional to/ changes at about the same speed as its number, N, where the turns are numberedbeginning from the bottom turn and ending at the top. The shear stress τ in each turn(9) is totally different / varies from zero at the centre of the turn (axis of the coil) toa maximum value at the edge of the coil. The average local strain rate (10) is thus / must be kind of related to the spacing between turns, s, and the time, t.
10. Write a description of a chemical experiment you have carried out recently. Use the words and phrases from previous exercises to help you.

Text 3
Active Vocabulary

make observations (phr) – делать наблюдения

notice (v) – замечать, обращать внимание

remain (v) – оставаться

take place (phr) – происходить, случаться, состояться, иметь место

require (v) – требовать(ся)

produce changes (phr) – вызывать изменения

draw a conclusion (phr) – делать вывод

conclude (v) – делать вывод, выводить заключение

state (v) – заявлять, утверждать, констатировать, формулировать

seem to (v) – казаться, представляться

account (n) – отчёт, сообщение, доклад

1. Think about an experiment you have done recently. Then in pairs, discuss 1–5.

1. 
   Briefly describe the experimental process.
   
2. 
   Explain what you predicted would happen.
   
3. 
   Describe what actually happened.
   
4. 
   Explain what you learned from the experiment.
   
5. 
   Explain what you did as a follow – up to the experiment.
   

2. When the report of the procedure of an experiment is complete, it is then necessary to describe the results, including the observations which were made, and then draw conclusions from the results. Here is a description of what was observed during the experiment and a conclusion based on the observations and results. Study it and answer the questions about the results.

Reporting Observations and Results. Stating Conclusions

The water in the calorimeter was observed carefully as the temperature approached 0 °C. It was observed that the temperature continued to fall for a short time without any ice forming. The temperature was seen to fall a few degrees below 0 °C while the water remained liquid. It was then noticed that the temperature rose to 0 °C and ice began to form. The temperature was found to remain constant at 0 °C when ice was present. The behaviour of the temperature of the water can be seen from the graph.

From the results, it can be seen that the temperature fell a few degrees below zero before ice formed. The temperature then rose to zero as the ice formed. A loss of temperature indicates a loss of heat energy, therefore it can be stated that as the temperature of the water fell below zero, the water continued to give out energy to the surrounding freezing mixture. Since the temperature rose as the ice formed, it can similarly be stated that energy was gained by the water as it became solid.

When the water froze, a change of state took place, as the water changed from a liquid to a solid state. It was noted that the temperature rose during this time. Heat energy must therefore have been absorbed by the water during the change of state.

It can therefore be concluded that energy was required in order to bring about a change of state in the water. The experiment demonstrates that energy is required to produce a change of state.

1. What was observed when the temperature was around 0 °C?

2. When did ice begin to form?

3. What does a fall in temperature indicate?

4. Why is it possible to state that energy was absorbed by the water as it solidified?

5. The water changed from liquid to a solid. What can we say took place?

6. What must have happened in order to produce this change?

7. How do we know this?

8. What is the conclusion of the experiment?
3. Read the sentence: The temperature continued to fall for a short time, but no ice formed. This is another way of saying: The temperature continued to fall for a short time without any ice forming. Study the following situations and then re-phrase the sentences using without.

1. 
   A metal wire was stretched 5 cm, but it didn't break.
   
2. 
   Mercury was cooled to –20 °C, but it didn't freeze.
   
3. 
   Sand was added to water and the mixture was heated gently for a long time, but the sand did not dissolve.
   
4. 
   Some aluminium was placed in water and left for some time, but no reaction was observed.
   
5. 
   A current was passed through a wire for a period of time, but no heating effect was detected.
   
6. 
   A substance was heated for a short time, but no rise in temperature was observed.
   
7. 
   Various substances were placed in diluted hydrochloric acid, but no gas was seen to be evolved.
   
8. 
   Some ammonium chloride was heated, but no ammonia was smelt.
   
9. 
   A lighted splint was held over the top of a test-tube of gas, but no explosion was heard.
   
10. 
    A suspended magnet was brought near to a coil of wire, but no effect was noticed on the magnet.
    

4 (a). Read the report of the results of an experiment and put the paragraphs in the correct order.

A) Since, at the end of the experiment, the level of solution in each cylinder was higher than the level of water in the beakers, it can be stated that the membrane must be capable of supporting a certain pressure of solution and preventing the solution from passing through it. Consideration of the diagrams showing the results of the experiment will show that there is a pressure of Xcm of solution acting on the membrane supporting the solution of concentration 5gdm‾³ and a pressure of 2Xcm acting on the membrane containing the solution of concentration 10gdm³. There will also be atmospheric pressure acting on both of the membranes.

B) If the membranes were punctured, the solutions would flow into the beakers until the levels of liquid inside and outside the cylinders were equal. It therefore seems that there is a driving force which causes the water molecules to pass through the membrane into the solution. However, the passage of water molecules through the membrane clearly stopped at some point when the column of solution reached a certain height. This can be explained as follows: as the column of solution rises up the cylinder, the pressure acting on the membrane will increase. When this pressure is equal to the driving force causing the water molecules to move across the membrane into the solution, a state of equilibrium is obtained. This means that there are "the same number of water molecules crossing the membrane from either side and so the height of the column of solution will not increase further.

C) It appears that water has been transferred through the membranes into the cylinders during the experiment, causing the levels of solution inside the cylinders to rise. Since the membranes used were semi-permeable, no protein could have passed into the solvent in the beakers. The movement was therefore from the solvent across the membrane into the cylinders.