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UNIT 4 ALLOYS

Vocabulary

• revision of the vocabulary

• Word formation: Nouns from verbs

Grammar and functions

• Defining and explaining

• Relative clauses

• WHAT vs WHICH

• Shortened relative clauses

TRANSLATION: METALS

Read the text and decide how best to translate the expressions given below.

1. usan los ingenieros 2. tantos metales 3. Hay 4. ofrece 5. F

ue

5.fuerza 6. su fuerza y tenacidad

Why DO ENGINEERS USE (1) SO MANY METALS (2) today when

THERE ARE (3) other materials, especially plastics, which are

available? A material is generally used because IT OFFERS (4)-------------------

the required STRENGTH (5) and other properties at minimum cost.

Appearance is also an important factor. The main advantage of metals is --------- THEIR STRENGTH AND TOUGHNESS (6). CONCRETE (7) may be cheaper and

FREQUENTLY/OFTEN USED (8) in building, but even concrete DEPENDS ON (9)

its core/nucleus of steel for strength.

7.El hormigón 8. se usa a menudo 9.depende de 10. más ligeros y más resistentes a la corrosión 11.qué tenemos que hacer 12. pueden descomponerse (TO BREAK DOWN) 13. débiles 14. se mezclan 15. una aleación 16. que es mucho más fuerte 17. obtener 18. una serie de diferentes

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Plastics are LIGHTER AND MORE/BETTER CORROSION RESISTANT/RESISTANT TO CORROSION (10) but they are not usually as strong. Another problem with plastics is WHAT (WE HAVE) TO DO (11) with them after use. Metal objects CAN BE BROKEN (12) down and the metals recycled;

plastics can only be dumped or burned. Not all metals are strong, however. Copper and aluminium are both

fairly WEAK (13), but if (THEY ARE) MIXED (14) together, the result is AN ALLOY (15) called aluminium

bronze, WHICH IS MUCH/FAR STRONGER (16) than either pure copper or pure aluminium. Alloying is

an important method of OBTAINING/ACHIEVING/(GETTING) (17) whatever special properties are

required: strength, toughness, resistance to wear, magnetic properties, high electrical resistance or corrosion

resistance.

The properties of a metal can be further improved by use of heat treatment. Heat treatment is the term given to

A SERIES/GROUP/NUMBER/SET OF DIFFERENT (18) procedures IN WHICH (19) the properties of

metals and alloys are changed. It usually CONSISTS OF/IN HEATING (20) the metal or alloy to a selected

temperature BELOW ITS MELTING POINT (21) and then COOLING IT (DOWN)/LETTING IT COOL (22) at a certain rate to obtain those properties which are required. For example, hardening is used to

make metals harder. Tempering MAKES THEM SOFTER AND LESS BRITTLE (23)

Annealing is carried out to make a metal soft so that it can be machined MORE EASILY (24).

It is easier to machine more easily machined more easily machineable

(IN) THIS WAY/THUS (25), metallic materials can be produced to meet every kind of engineering

specification and requirement. Meet specification/requirements=to fulfil full+fill

Methods of extracting, producing and treating metals ARE BEING DEVELOPED (26) all the time to meet engineering requirements. This means that there is an enormous variety of metals and metallic materials FROM WHICH TO CHOOSE/TO CHOOSE FROM (27)

18. una serie de diferentes 19. en los que 20. consiste en calentar 21. por debajo de su punto de fusión 22. enfriarlo 23. los hace más blandos y menos quebradizos 24. más fácilmente 25. De esta forma 26. se están desarrollando 27. de los que elegir

CONCRETE 7)-------- may be cheaper and (IT) IS OFTEN/FREQUENTLY/WIDELY/COMMONLY/(USUALLY)

USED 8) in building, but even concrete DEPENDS ON (9) its core of steel for strength.

Plastics are LIGHTER AND MORE CORROSION RESISTANT (10) but they are not usually as strong. Another

problem with plastics is –WHAT (WE HAVE) TO DO (11) with them after use. Metal objects –CAN BE

BROKEN (12) down and the metals recycled; plastics can only be dumped or burned.

Not all metals are strong, however. Copper and aluminium are both fairly WEAK/BRITTLE(13), but if THEY

ARE MIXED (14) together, the result is AN ALLOY (15) called aluminium bronze, WHICH IS MUCH/FAR

STRONGER (16) than either pure copper or pure aluminium. Alloying is an important method of OBTAINING

(17) whatever special properties are required: strength, toughness, resistance to wear, magnetic properties,

high electrical resistance or corrosion resistance.

7.El hormigón 8. se usa a menudo

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9.depende de 10. más ligeros y más resistentes a la corrosión 11.qué tenemos que hacer 12. pueden descomponerse (TO BREAK DOWN) 13. débiles 14. se mezclan 15. una aleación 16. que es mucho más fuerte 17. obtener 18. una serie de diferentes 19. en los que 20. consiste en calentar 21. por debajo de su punto de fusión 22. enfriarlo 23. los hace más blandos y menos quebradizos 24. más fácilmente 25. De esta forma 26. se están desarrollando 27. de los que elegir

The properties of a metal can be further improved by use of heat treatment. Heat treatment is the term given to

A SERIES/GROUP/NUMBER/SET OF DIFFERENT 18) procedures IN WHICH (19) the properties of metals

and alloys are changed. It usually CONSISTS OF/IN HEATING (UP) (20) the metal or alloy to a selected

temperature BELOW ITS MELTING POINT (21) and then COOL IT (DOWN) (22) at a certain rate to obtain

those properties which are required. For example, hardening is used to make metals harder. Tempering –

MAKES THEM SOFTER AND LESS BRITTLE (23) Annealing is carried out to make a metal soft so that it can

be machined (MORE) EASILY (24). SO/THUS/(IN) THIS WAY(25), metallic materials can be produced to meet

every kind of engineering specification and requirement.

Methods of extracting, producing and treating metals ARE BEING DEVELOPED (26) all the time to meet

engineering requirements. This means that there is an enormous variety of metals and metallic materials

FROM WHICH TO CHOOSE (27)------------------

Make a list of all the properties given in the text and write down the corresponding NOUN or ADJECTIVE for each of them

STRENGTH- STRONG WEAKNESS-WEAK BRITTLENESS-BRITTLE LIGHTNESS-LIGHT RESISTANCE-RESISTANT MAGNETISM-MAGNETIC HARDNESS-HARD

Resistance to wear = to wear – wore – worn Worn out

GIVING DEFINITIONS: RELATIVE CLAUSES

When defining, we normally mention a specific item which belongs to a general class and then we add the characteristics which make that item different from the other members of the class. The main structure used in definitions is the RELATIVE CLAUSE.

FUNCTION SUBJECT OBJECT POSSESSIVE PREPOSITION

DEFINING that (which/who)

that(0) whose + NOUN NOUN + of which

PREP + which

NON-DEFINING

which (who)

which (whom)

whose + NOUN NOUN + of which

PREP + which

The elements that/which compose steel are iron and carbon Iron, which is a component of steel, is a common metal Iron and carbon, of which steel is composed, have different properties , which steel is composed of, Steel, whose components are iron and carbon, is a metal , the components of which are iron and carbon, is a metal

An ITEM is a GENERAL CLASS: -Which(that)+vb-s: Stainless steel is an alloy WHICH/THAT DOES NOT CORRODE. -Which(THAT)+IS VB-ED: Al. is a metal WHICH/THAT IS PRODUCED from bauxite.

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-PREP+WHICH: Acoustics is a branch of physics IN WHICH sound is studied.

A. The structure PREP+REL is very common in Scientific English. Decide which is appropriate.

1. The nucleus is the part of the atom (around which/to which/by which) smaller particles rotate.

2. Corrosion is a process (which/by which/of which) cannot be totally avoided.

3. The magnitude of a force is equal to the number of grams constituting the mass (at which/on which/about which) it acts multiplied by the number of cm/sc.

4. Polymers are the elements (on which/in which/ which) plastics are based

5. Dynamics is a discipline (in which/which/for which) movement is studied in detail.

6. The coating (with which/at which/in which) the system is covered costs ten thousand pounds.

7. A thermostat is a device (on which/around which/with which) temperature can be controlled.

8. A thermometer is a device on which temperature can be displayed

9. Our engineers are designing a technique (for which/by which/which) energy loss can be significantly decreased.

10. The way [(at which/in which/for which)] these components are assembled is not the ideal one.

11. The glass (which/from which/by which) retorts are made must be fire-proof

12. A container of hot water gives off heat to the objects (which/by which/in which) it is surrounded.

13. The melting point is the temperature (in which/by which/at which) metals change from solid to liquid

1. Strength is the main property which/that steel offers. 2. The process that/which is known as polymerization consists of joining different polymers

of/by which plastics are composed. 3. Electrons, the electrical charge of which/(whose electrical charge) is negative, are the

responsible particles for the production of electricity. 4. The high speeds at which the rotor in a generator turns produce large amounts of

electricity. 5. An electrolytic cell is the place in which/(where) the electrolytic process takes place. 6. The discovery of semiconductors allowed the mass production of chips, which reduced

the cost of computers significantly. 7. Lead, whose symbol is Pb, is the heaviest metal. the symbol of which

8. There are many different ways in which we may change the properties of materials.

B. Join these sentences with the appropriate relative structure 1. Atoms are the particles by/of which all matter is composed. 2. Strength is the main property which/that/0 steel offers. 3. The process which/that is known as polymerization consists of joining different polymers

of/from which plastics are made. 4. Electrons, the electrical charge of which is negative [whose electrical charge is negative],

are the responsible particles for…electricity. 5. The high speeds at which the rotor in a generator turns produce large amounts of electricity. 6. An electrolytic cell is the place (where)/in which the electrolytic process takes place. 7. The discovery of semiconductors allowed the mass production of chips, which reduced the

cost. 8. The temperature at which iron melts is 1550ºC. 9. Lead whose symbol is Pb, is the heaviest metal.

10. There are many different ways in which we may change the properties of materials. 11. The lower part of the atmosphere, (where)/in which weather phenomena occur, is known as.. 12. Ductility is the main property that/which/0 copper possesses

that which who whose 0 PREP+which

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that/which

that/which OF/BY which

(WHOSE electrical charge)

OF which

AT which

In which where

which

whose

In which

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SHORTENED RELATIVE CLAUSES

SHORTENED RELATIVE CLAUSES are very common in technical texts. Relative clauses can ONLY be shortened when the Relative Pronoun is the SUBJECT of the relative clause. There are two possibilities:

When the verb in the Relative clause is in the passive voice = VB-ED Aluminium is a metal that/which is produced from bauxite => Aluminium is a metal PRODUCED from bauxite.

When the verb in the Relative clause is in the active voice = VB-ING: A tangent is a straight line that/which touches a curve. => A tangent is a straight line TOUCHING a curve

Tin is a metal BELONGING to the carbon group WHICH/THAT BELONGS The triangle, WHICH IS SURROUNDED by a circle, represents the nucleus SURROUNDED The circle WHICH SURROUNDS the triangle contains electrons The circle SURROUNDING the triangle...

Steel is an alloy that/which consists of Fe and C CONSISTING OF

EXERCISES

SHORTENED RELATIVE CLAUSES Write the verb in brackets in the -ED or -ING form

1. Alloys are materials CONTAINING (CONTAIN) at least one metal. 2. The cables SUPPLYING (SUPPLY) the electricity were damaged in the storm. 3. This report contains the results OBTAINED (OBTAIN) from the test. 4. The temperatures SHOWN (SHOW) in the graph are given in degrees centigrade. 5. Coolant NOT FLOWING (NOT FLOW) through the radiator may cause overheating. 6. The mixture FED (FEED) to the machine is then processed. 7. We analyzed the samples TAKEN (TAKE) from polluted water. 8. A new synthetic material DEVELOPED (DEVELOP) last year is already being produced on a commercial scale. 9. The metal SURROUNDING SURROUND) the engine must resist high temperatures. 10. The metals KNOWN (KNOW) as ferrous metals, contain iron.

1. The test-tube CONTAINING the solution

The solution CONTAINED in the test tube 2. The cables SUPPLYING the electricity

The electricity SUPPLIED by the cables 3. This report contains the results OBTAINED

from the test. 4. The temperatures SHOWN in the graph are. 5. The liquid FLOWING through the pipe is low

grade oil. 6. The mixture FED to the machine is then

processed.

7. We analyzed the samples TAKEN from polluted water.

8. A new synthetic material DEVELOPED last year

9. The metal SURROUNDING the engine must The engine SURROUNDED by the metal

10. The metals KNOWN as ferrous metals

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NON-DEFINING RELATIVE CLAUSES

The elements that/which compose steel are iron and carbon Iron, which is a component of steel, is a common metal Iron and carbon, of which steel is composed, have different properties

Steel, whose components are iron and carbon, is a metal , the components of which are iron and carbon, is a metal The circle SURROUNDING the triangle has electrons The triangle SURROUNDED by the circle is the nucleus

In NON-DEFINING RELATIVE CLAUSES the relative pronoun WHICH (WHO) cannot be

replaced by THAT. They usually follow a comma. Remember that when the Rel. Pronoun is replacing an entire sentence, it is ALWAYS a Non-

Defining Relative Clause, and therefore the only possibility is WHICH:

E.g.: One of the most commonly used metals is steel, WHICH consists of Fe and C. We cool the metal slowly, WHICH releases the internal stresses.

Note the difference between WHAT and WHICH. WHICH always needs a specific

reference in the previous sentence whereas WHAT has no specific reference at all.

I gave her just what she needed John got the job, which surprised everybody

What I’d like is a digital watch Steel, which is an alloy of Fe and C Do you want to hear what she said?

USES of THAT

THAT has 4 main uses: (+1) (+Demonstrative adjective)

• Relative pronoun (THAT or WHICH) : e.g. The materials (THAT /WHICH are) used in structures must be very strong

• Conjunction: THAT (after vbs such as TO SAY, TO STATE, TO KNOW). E.g. She said THAT it was raining

• Pronoun (= THE ONE(S) usually with adjectives): THAT / THOSE. They are generally used in comparative constructions and are normally followed by preposition or shortened relative clause (THAT/THOSE + Rel Clause or Prepositional phrase = el(los) que // el(los)de :

I like the blue bag but not the RED ONE The density of iron is higher than THAT OF/the one of zinc The results are better than THOSE/the ones presented last year The properties of alloys are better than those/the ones of their components I have two articles. I think I’ll read that/the one about materials first

EXERCISE

The melting point of Hg is far/much lower than that of the rest of metals

(the melting point of the rest of metals)

The melting points of alloys are usually higher than those of their components

Decide the function of THAT / THOSE in the following sentences

1. The microscope showed that the membrane of TiNi was thicker than that of stainless steel

2. The result is a plethora of choices that enable today’s engineers to fine-tune the selection process

3. Natural materials such as obsidian and tektites have compositions and properties similar to those of synthetic glass.

4. Plastics have a lower melting point than that of metals

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5. The results obtained in the experiment are compared to those given in the specifications

6. The toughness and hardness of a steel that is not heat treated depend on the amount of carbon that is added to the mixture

7. The results that were obtained during the experiment show clearly that the elasticity of steel is higher than that found in pure iron.

8. this alloy has a high tensile strength, comparable to that of the duplex stainless steels Engineers must choose the materials that they consider best suited for a particular purpose

9. Wilm discovered that the alloy increased in hardness when left to age at room temperature

10. Polymers can never have a degree of order equivalent to that of low molecular materials like ice or common salt

. EXERCISES

A. Decide whether WHAT or WHICH should be used in the following sentences

1. The mixture of copper and tin is WHAT is known as bronze, WHICH was probably the first alloy used by man.

2. We need to benefit from solar energy, WHICH is difficult in some countries.

3. They were not surprised at WHAT this device can detect, because they knew WHAT to expect.

4. The maintenance engineers did WHAT they could, WHICH wasn't much.

5. Many companies don’t know WHAT to do with their waste, WHICH makes for serious environmental problems.

6. He is familiar with several programming languages, WHICH makes him suitable for the job.

7. We don’t know WHAT caused the accident in the power plant.

8. WHAT goes up must come down.

9. It doesn’t matter WHAT you do, the system won’t work properly anyway.

10. I am sure that WHAT the technicians say is correct, but we should look for better alternatives to provide clean energy. (TO PROVIDE THE CITY WITH CLEAN ENERGY/ TO SUPPLY)

EXERCISES

A. Join these pairs of sentences by means of a relative. Use shortened relative clauses whenever possible.

1. H.Oersted discovered the relationship between electricity and magnetism. He was a Danish scientist.

2. Light moves at 300.000 Km/s. (The speed..... (a la que se mueve la luz ...)

3. An atom has a nucleus. Electrons orbit around the nucleus.

4. The figure shows an apparatus. It is used to measure the specific heat of a metal.

5. Steel contains very little carbon. It is known as mild steel.

6. Venus is a planet. The surface of Venus is thought to be at least 200ºC

7. An axis is an imaginary line. A body rotates around this line.

8. Conductors are a kind of material. Electricity flows through them.

9. Electrons, protons and neutrons make up an atom. An atom is composed of these particles. (Electrons, protons and neutrons are the particles ....)

10. Steel consists of carbon and iron. Steel is an alloy. B. Here are some of the most common mistakes made by students when using relative clauses.

Correct the wrong sentences (Not all sentences have mistakes, and some sentences have more than one mistake).

1. The properties of an alloy depend on the materials that IT contains.

2. Electrons orbiting farther from the nucleus are (MORE) easily drawn away.

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3. An electrolytic cell is the place in which ELECTROLYSIS takes place.

4. Alloying is a process in which several metals are involved.

5. Steel is an alloy WHOSE composition consists of carbon and iron.

the composition of which

6. Go on with what you were doing.

7. A compiler is the name GIVEN to the software that translates a program into machine code.

8. Conductors are materials which electricity can flow through./THROUGH which electricity can flow

9. The mixture of copper and zinc is called brass, (WHICH IS) the most common non-ferrous alloy.

10. Metals can be heated (UP) to a certain temperature above which their properties change.

11. The temperature AT WHICH iron melts is 1,550ºC.

12. The amount of electricity generated depends on the speed in which THE ROTOR turns the rotor.

LISTENING: ALLOYS

An alloy is a COMBINATION OF METALS with each other or with nonmetals, such as CARBON or phosphorous, and formed by MIXING the molten components. The properties of an alloy can be adjusted by varying THE PROPORTIONS of the constituents. Very few metals are used today IN (THEIR)/(A) PURE STATE. The most common alloys are the different forms of STEEL, all of which contain a large proportion of IRON and small amounts of CARBON and other elements. For example, alloy steel is CARBON STEEL to which various elements, such as CHROMIUM, COPPER, cobalt, manganese, molybdenum, NICKEL, tungsten or vanadium, have been added in sufficient amounts TO OBTAIN THE DESIRABLE PHYSICAL AND chemical properties. BRASS AND BRONZE, two well-known alloys of COPPER, are still used in industry. The properties of an alloy DEPEND ON THE PROPERTIES OF THE ELEMENTS (THAT) IT CONTAINS although the alloy behaves in a different way. For example, there is an alloy of IRON THAT IS EVEN MORE MAGNETIC THAN PURE IRON The usual method of making an alloy is to heat the different elements UNTIL THEY MELT (UP TO THEIR MELTING POINTS), then to mix them. Thus, an alloy is a solution RATHER THAN A SIMPLE MIXTURE. As you know, the properties of a solution are not simply a mixture of the properties of its components. Water for example, FREEZES AT 0ºC and sodium chloride MELTS AT 801ºC, but if sodium chloride is dissolved in water to form a strong solution of salt, THIS SOLUTION FREEZES AT –23ºC. In fact/ACTUALLY, as a general rule, A SOLUTION FREEZES AT A LOWER TEMPERATURE THAN ITS COMPONENTS (DO). And since alloys are SOLID SOLUTIONS, it should not surprise you to learn that THEY BEHAVE IN A SIMILAR WAY: an alloy usually has A LOWER MELTING POINT than the substances OF WHICH IT IS COMPOSED. For example, PURE IRON MELTS AT 1,500ºC and carbon at 3,350ºC, but cast iron, an alloy of iron and carbon, melts at 1,150ºC.

VIDEO: THE PERIODIC TABLE

One of the most striking elements in the earth's crust is gold. Its rarity, lustre, and resistance to corrosion make

it an ideal symbol of value and one that has underpinned the world's currencies throughout history. But there are

other uses for gold, such as in dentistry or microcircuitry, which indicate that the full understanding of the

properties of elements is needed to appreciate the true worth to technology. One of the most important clues to

these properties comes from the periodic table.

In this program, we're going to look at the periodic table and see how the order it imposes of elements gives us

a way of interpreting their properties. We can think of the elements around us rather like a group of chess

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pieces. Observed without context, their individual properties seem rather random, interesting, but hard to

deduce much. If we can impose the right framework, we can see an underlying structure that gives the relative

properties of each piece some meaning. If you're a chess player, you can see it's check mate. White is mated.

The sheer variety of elements is of course greater than that of the chess pieces and we're going to start off by

exploring how some of them behave, beginning with the most common element of all, oxygen.

The bubbles on the leaves of this plant are oxygen. It's a colourless, transparent gas. It's because air contains

some oxygen that our fires burn. If this splint is tapped out the oxygen in the jar recandles it. To stay alive, we

have to breathe oxygen gas.

But this element, chlorine, is a gas that we mustn't breathe. It was the first of the war gases. In the I World War,

thousands of men were killed or maimed in chlorine gas attacks.

There are two more chemical elements in these balloons: the red one contains hydrogen, the yellow one helium.

They are both colourless transparent gases, and both are lighter than air. Because of this property, both

elements were once put to a particular use, and still are at fair grounds. But in their chemical behaviour,

hydrogen and helium couldn't be more different. Hydrogen burns with a fiercely hot flame… Disasters like this

would never have happened if helium had been used instead of hydrogen. Helium doesn't burn. Indeed, it

doesn't react with anything. So today's manned balloons are lifted by helium. But most of the chemical elements

are not gases, but solids. A few solid elements are non-metals, like sulphur, which sometimes occurs beside

volcanic springs.

These two probes are wired to an electric bell. I can use them to find out if things conduct electricity. Now here's

a very handsome-looking lump of sulphur. I'll patch the probes across it. Well, that doesn't ring any bells.

Sulphur is a non-metal, and non-metals hardly ever conduct electricity. Now, here's a lump of aluminium.

Aluminium is a metal and metals are good conductors. Now, most of the solid elements are metals like

aluminium. Yet even among the metals there's great variety of behaviour. Mercury is a liquid at room

temperature. Caesium melts in the hand. To melt iron, you need a furnace as hot as this. And much, much

higher temperatures are needed to melt this element, tungsten, the metal with the highest melting temperature

of all. Here are five of the six noble gases: helium, neon, argon, krypton and xenon.

They're all colourless and transparent. Krypton and xenon form compounds only with difficulty. Helium, neon

and argon don't form compounds at all. As we descend the group in the periodic table, the atomic number, and

their relative atomic mass, increases, the gases get denser. Helium is lighter than air. Neon is just light. Argon

and krypton, I've just got to unstick these from the anchorage for a moment, argon and krypton are both heavier

than air and xenon, xenon is the heaviest of the lot. You heard of a lead balloon? Well, this is it.

One of the most striking elements in the earth's crust is__________. Its ___________ (RARE), lustre,

and ______________________make it an ideal symbol of value and one that has underpinned the world's

currencies throughout history. But _________________________, such as in dentistry or microcircuitry,

_______________ that the full ____________________ (UNDERSTAND) of

___________________________is needed to appreciate the true worth to _______________.

_______________clues to these properties comes from _________________________.

In this program, we're going to look at the periodic table and see _______________it imposes of

elements gives us ________________________ ___________. We can think of the elements around us

______________________ a group of chess pieces. Observed without context,

_____________________________ rather random, _______________, but _______________to deduce

___________. If we can impose the right framework, we can see an underlying structure _______________ the

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relative properties of each piece some meaning. If you're a chess player, you can see its check mate. White is

mated.

The sheer variety of elements is of course _______________that of the chess pieces and we're going to

start off by exploring ______________________________ _______, beginning with

_______________________________________________.

The bubbles on the leaves of this plant ____________________. It's _______________,

_______________. It's _________________________________ ___________ that our fires burn. If this splint

is tapped out, the oxygen in the jar recandles it. To stay alive, we

__________________________________________.

But this element, _______________, is a gas _________________________ _____. It was the first of

the war gases. In the I World War, _____________ ______________were killed or maimed in chlorine gas

attacks.

There are ______________________________________________: the red one contains

_______________, the yellow one _______________. They are both _______________________, and both

are _______________________________. ________________________________, both elements were once

put to a particular use, and they still are at fair grounds. But __________________________________ ,

hydrogen and helium couldn't be ________________________________________ __________with a fiercely

hot flame…

Disasters like this __________________________

_____________________ if helium had been used

_____________________________________________. Indeed, it doesn't

_______________with anything. So today's manned _________

__________________________ are lifted by helium.

But _____________________________________,

_______________________________ but solids.

____________________________ are non-metals, like sulfur, ______________________ beside volcanic

springs.

Only for Amparo Diaz's students WRITING UNITS 2-3-4

Compare in 150 words alloys and pure metals(you can do a general comparison, compare an alloy with its components or compare an alloy and a pure metal) INCLUDE and UNDERLINE AT LEAST

-2 SHORTENED RELATIVE CLAUSES (-ED/-ING) (p. 50)

-3 other different types of RELATIVE CLAUSES. (pp.49, 51 & 52)

-2 VB from adjectives/nouns (-EN-) (p.36)

- 8 different expressions of comparison-contrast (pp. 39 & 42)

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EXTRA READING

WHAT IS HOT IN METAL ALLOYS

Let’s look at some of the new metal alloys which are being developed as materials for construction.

Recommending a material with the outmost in corrosion resistance may be the safest bet for certain process environments, but in most applications it may be tantamount to “gold plating.” Given the wide variety of new alloys available today, an alternative material may be a better choice. True, the latter option may not offer the lowest in corrosion rates, but may do the job within budget while satisfying the specified process requirements. (...)

Using new technologies, the manufacturers can now do several things: Lower carbon content economically; add nitrogen easily as a deliberate alloying element; reduce the amount of tramp elements (undesirable residuals that get carried along with the raw materials) significantly; and precisely control the amount of major alloying elements. The result is a plethora of choices that enable today’s engineers to fine-tune the selection process more precisely to the specific requirements of a particular process condition. And with this frequently comes a notable cost saving.

Nowadays, one can often consider the current selection process of less-costly alloys as an almost continuous progression of small steps, each step containing one or more alloys of increasing corrosion resistance. Austenitic stainless steels, also known as the Type 300 series stainless steels with 18% chromium, 8 to 10% nickel and often some molybdenum, still remain the corrosion-resistant workhorses for the chemical process industries (CPI). However, austenitic stainless steels with higher molybdenum contents, and therefore with more corrosion resistance are now finding increasing applications. Maybe the biggest news is the superaustenitics, in particular those called “6 Mo,” referring to their nominal molybdenum percent. These materials have made a very impressive impact given their good resistance to pitting and crevice corrosion, and new proprietary superaustenitics are still being introduced.

Among the nickel-based alloys that contain large chromium and molybdenum contents, Alloy C-276 (also known as Alloy 276) continues to be the mainstay. But here too, special compositions have come on the market and are finding specific niches, especially in cases when resistance to pitting, crevice corrosion, intergranular attack, and stress corrosion cracking or to mixed-acid solutions of an oxidizing nature are of particular importance. In addition to fatigue-resistant alloys (used in many CPI piping systems) and age-hardenable alloys (heat-treated so that ductility and toughness remain high), cobalt-based alloys are being developed to offer high corrosion- and wear-resistance to many aggressive environments. One example is Ultimet which has good resistance to cavitation erosion, slurry erosion and galling. Also, this alloy has a high tensile strength, comparable to that of the duplex stainless steels, which are traditionally used in situations requiring high resistance to chloride stress corrosion cracking (CSCC) and high mechanical properties. Other examples of newer alloys are those initially designed for handling chloride-containing chemicals in the pulp-and-paper industries and for seawater-cooled heat exchangers in electric power utilities. These new alloys have been found to be most useful for containing various highly corrosive fluids in vessels, piping and exchangers in the CPI.

To all this, add several new titanium alloys. Unalloyed titanium, referred to as chemically pure or C.P., has outstanding resistance to general and other forms of corrosion in many environments. But it is not resistant to crevice corrosion. A small amount of palladium markedly increases titanium’s resistance to this form of attack. Ti Grade 1 is one example of chemically pure titanium with high formability and ductility but lower strength. Another example is Titanium Grade 9 which has been recently approved for applications including pressurized service equipment.

Now instead of big jumps between candidate-materials groups, there are many stainless steels and alloys being offered with a spectrum of corrosion characteristics. Though the difference in corrosion resistance of a new alloy may be somewhat small compared with the older ones, this extra performance can often be the critical factor to the success of a project.

Source: “What’s hot in metal alloys: Materials of construction report: part 1” by Warren I. Pollock, Chemical

Engineering, October 1992, pages 78-88.