Transcript UNIT 2 CLASSIFICATION

UNIT 3
COMPARISON & CONTRAST
Vocabulary
• Properties of Materials (Adj / Nouns / Vbs)
• WORD FORMATION: N/VB from ADJ
Grammar and functions
• Comparison: special structures
• ADJ vs ADV
• Comparing & Contrasting: connectors
PROPERTIES OF MATERIALS
• COPPER
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A non-ferrous metal
high electrical and thermal conductivity
high tensile strength
Ductile & malleable
• ZINC
•
– A non-ferrous metal
– low hardness & Very corrosion resistant
– A relatively heavy metal, but lower density than cast iron, copper or
lead
– relatively high fusibility but lower than that of lead
LEAD
– High density
– Melts very easily
– Low tensile strength
• ALUMINIUM
– Low density
– Ductile & malleable
– Relatively low tensile strength
Adj VS Adv
Such a concentration of lead is highly dangerous for
men.
2.- Hard steel is generally preferred when building huge
bridges.
3.- Magnesium is known as a metal which burns easily.
4.- The cable is to be covered by a thin rubber coating.
5.- Stainless steel consists of slightly high proportions of
chromium.
6.- If you put a pipe here, it should not be easily bent./
7.- This alloy performs well due to its exceptional
electrical conductivity.
8.- Researchers found extremely rare compounds on
Mars.
9.- Chalk is a good example of a soft material
10.- Protons are positively charged particles.
1.-
EXCERCISE: Comparison
1. As copper has become RARER and MORE EXPENSIVE, aluminium has
come into use even though it has a HIGHER resistance THAN copper.
2. In early days, people thought that the electric current flowed in THE SAME
way AS water
3. In Volta's cell, one of the metals is chemically MORE ACTIVE THAN the
other and gives off electrons which are attracted by THE LESS ACTIVE
metal.
4. If we let the bar cool FASTER than before, we obtain a metal which is
HARDER and MORE EASILY machineable.
5. Hydrogen is one of THE LIGHTEST elements while uranium is one of THE
HEAVIEST.
6. Electrons orbiting FARTHER from the nucleus are those which are MORE
EASILY drawn away.
7. In generators, THE FASTER the wires move, THE GREATER the
generation of emf.
8. Thermoplastics can be reheated AS MANY times AS required.
9. MOST (OF THE) scientists use computers in their work.
10. Oil is THE MOST WIDELY USED energy source
11. There are .SO MANY materials that we can always find the appropriate one
for our needs
12. We spend SO MUCH energy in producing electricity that we should
concentrate our efforts on other possibilities to generate it
EXERCISE: Comparison
Cast iron is the least malleable of these metals.
Similarly, high carbon steels are not very malleable
with less carbon, steels become more malleable.
Med. C steels are more malleable than H.C. steels.
Low carbon steels have even more malleability.
Wrought iron is the most malleable of these ferrous metals.
Wrought iron is also the most elastic of these metals.
L. C. steels are less elastic because they contain more carbon.
Medium carbon steels are less elastic than low carbon steels.
H. C. steels have less elasticity because they have more carbon
Cast iron has much carbon in it and therefore it is the least elastic.
The more C these contain, the less malleable and elastic they are.
W iron contains very little/the least C and it is the most elastic.
Cast iron contains more/the most carbon and it has the least
elasticity.
EXERCISE: expressions
• If we...COMPARE.. wrought iron and cast iron, we may find
some...SIMILARITIES..
• Both of them are ..SIMILAR IN THAT....they contain iron;
wrought iron, . LIKE/IN THE SAME WAY AS/SIMILARLY TO
cast iron,
• HOWEVER..., .ALTHOUGH they are very....SIMILAR IN ....
their composition, we may notice some ...DIFFERENCES...
REGARDING/WITH RESPECT TO/ AS REGARDS their
properties;
• thus ,wrought iron is very malleable, WHEREAS/WHILE cast
iron is THE LEAST MALLEABLE of all ferrous metals
• .. ON THE OTHER HAND, cast iron ...DIFFERS FROM
wrought iron in elasticity because WHEREAS/WHILE the
former has a very poor elasticity, the latter is very elastic.
• The..DIFFERENCE between these two metals comes from the
different amount of carbon content: THE HIGHER the content
of carbon, THE LESS MALLEABLE AND ELASTIC these
metals are.