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- Concepts
- Alloy, density, strength, brittle, corrosion, ductile, malleable,
conductivity, additive, steel, carbon steel, alloy steel, mild steel,
stainless steel
- Skills
- Core:
- Name uses of aluminum and relate them to its properties
- Describe the conversion of iron into steel using basic oxides and
oxygen
- Describe the idea of changing the properties of iron by the controlled
use of additives to form steel alloys
- Name uses of mild steel and stainless steel
- Describe the reasons for the use of copper and (steel-cored) aluminum
in cables, and why plastics and ceramics are used as insulators
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- Extension:
- Name uses of copper and relate them to its properties
- Name uses of zinc for galvanizing and making brass
- Account for the apparent unreactivity of aluminum in terms of the oxide
layer which adheres to the metal
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- One of the common usage of a metal is as an alloy.
- An alloy is a mixture of two or more metals.
- Most alloys are mixtures of two different metals
- For example bronze (copper and tin) but other alloys such as mild steel
also contain non-metals (such as carbon).
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- They are produced by mixing the molten metals and allowing them to cool
slowly.
- Notice that there are empty spaces within the lattice of a metal.
- These empty spaces can be filled with atoms (ions) of another metal and
that is the structure of an alloy.
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- Here are some of the reasons why alloys are used in everyday life:
- Alloying strengthens a metal.
- For example, gold is a very soft metal, but if it is alloyed with
copper it becomes much stronger.
- That is because the empty spaces in gold would now be occupied by
copper ions making it more compact and thus giving it more strength.
- Copper is also a soft metal.
- It is often mixed with small amounts of zinc to make a much harder
alloy called bronze.
- Alloys can be designed to have different physical properties.
- For example, iron is strong but it corrodes easily.
- But when iron is mixed with chromium (and nickel) an alloy (stainless
steel) is formed which cannot corrode.
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- 1. White with a bluish tinge
- 2. melts at 658°C
- 3. very light (low density), but is strong, possesses great toughness
and tensile strength
- 4. malleable, ductile, can be easily bent and shaped
- 5. resistant to corrosion
- 6. good conductor of heat and electricity.
- 7. can be polished to achieve a highly reflective surface.
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- 1) Low density and strength make it ideal for construction of aircraft,
lightweight vehicles, and ladders.
- An alloy of aluminium called Duralumin is often used instead of pure
aluminium because of its improved properties,
- 2) Easy shaping, corrosion resistance (to natural acids), resistance to
weathering and low density make it a good material for a host of uses
such as
- Food packaging (drink cans) uses anodized aluminum (aluminum with
artificially thickened oxide layer by electrolysis)
- External structures such as roofing materials, electrical cables,
greenhouses and window frames.
- Often electrical cables are steel-cored aluminum wires
- 3) Good conduction of heat leads to its use for boilers, cookers and
cookware.
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- 4) Good conduction of electricity leads to its use for overhead power
cables hung from pylons (low density gives it an advantage over copper).
- 5) High reflectivity makes it ideal for mirrors, reflectors and heat
resistant clothing for fire fighting.
- Manufacture of steel, manufacture of alloys (bronze Al & Cu),
surgical instruments, Al-powder used in paint are some more uses of
aluminum.
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- Iron is one of the three magnetic metals (the others being cobalt and
nickel).
- Iron from the Blast furnace contains about 5% carbon which comes from
the coke in the furnace.
- It is therefore extremely brittle which means it is prone to shatter or
crack.
- However, it has a greater resistance to corrosion than either pure iron
or steel.
- It is cast into moulds called pigs, and the iron is called cast iron or pig
iron.
- Cast iron finds use as manhole covers.
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- The carbon in cast iron can be easily removed and controlled addition of
carbon to iron produces steel. (See next few slides.)
- Pure iron, which has had all the carbon removed, is called wrought iron.
- Wrought iron is malleable (easily shaped) and is mainly used in
ornamental work for gates.
- Iron is the catalyst in the Haber process (which you will study about
next year).
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- Carbon is removed from molten cast iron by bubbling oxygen through it in
a tilting furnace.
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- Impurities that do not produce gaseous oxides, such as silicon and
phosphorus, lime (CaO) is added to the furnace.
- The basic oxide of calcium react with the impurities forming a ‘slag,’
just as it does in the blast furnace when extracting iron from its ore.
- CaO(s) + SiO2(s) ® CaSiO3(l)
- The slag of course floats on top of the molten iron.
- The molten iron is poured off by tilting the furnace.
- Controlled amounts of carbon and other elements are added to make
different types of steel.
- The large majority of iron from the blast furnace is made into steel for
construction, steel contains 0.1% to 1.5% carbon.
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- The percentage of carbon determines the type of steel and therefore its
use.
- When carbon is alloyed with iron we call the alloy carbon steel.
- There are many different types of steel, it depends on the elements you
alloy iron with.
- The elements that are added to iron to convert it into an alloy are
called additives.
- Alloys contain more than one element and have the characteristic
properties of metals.
- Advantage with alloying is that the properties of the alloy surpass that
of the metal (iron in this case).
- Pure metals and alloys have different physical properties.
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- Mild steels for example contains less than 0.25% carbon.
- It is useful for chains, nails, car bodies, pylons etc.
- Other elements may also be added to make alloy steels.
- The most important iron alloy is stainless steel which contains Carbon,
Chromium, and Nickel.
- As it is tough and resistant to corrosion, it finds use in cutlery,
surgical instruments, kitchen sinks etc.
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- 1. An excellent conductor of electricity and heat.
- 2. Soft, easily bent and shaped
(malleable and ductile).
- 3. Resistant to corrosion (very unreactive).
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- 1. The main metal for electrical wiring (because of its ductility and
conductivity) and cables (because of its conductivity and resistance to
corrosion and weathering).
- 2. Copper cookware (not common).
- 3. Gas pipes.
- Being soft and ductile makes it an ideal material for pipes.
- 4. Water pipes.
- The same reason as 3.
- Also since copper is below hydrogen in the reactivity series, it does
not react with water.
- Copper is always used for plumbing in houses.
- Lead was used for plumbing in the past but has been replaced by copper
because lead compounds in water are toxic.
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- 5. Copper is mixed with other metals to form alloys, notably zinc for
brass, and tin for bronze.
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- Zinc is used in alloys such as brass (with combined with copper) and for
galvanizing (iron, which is used widely as roofing material). (See
Electricity & Chemistry: Electroplating.)
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- 1. J04/2/6 (d) The iron from the blast furnace contains up to 10% by
mass of impurities. The main impurities are carbon, silicon and
phosphorus. The diagram below shows one method of making steel from
iron.
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- (iii) The basic oxides react with the impurities in the iron and form
a slag. What information in the diagram suggests that the slag is less
dense than the molten iron? [1]
- (iv) Which one of the following is a basic oxide? Put a ring around
the correct answer.
- calcium oxide carbon
dioxide sulphur
dioxide water [1]
- (v) Why is steel rather than iron used for constructing buildings and
bridges? [1]
- (e) Special steels contain added elements such as vanadium, chromium,
cobalt or nickel. These are all transition metals.
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- State three properties of transition metals which are not shown by
non-transition metals. [3]
- (f) What is the name given to metals which are mixtures of more than
one metal? [1]
- 2. N03/2/2e. (e) The list below shows some of the substances which are
found in the liquid which drains through the waste.
- Aluminium Calcium carbonate
- Iron Lead
- Magnesium Nickel
- Sodium sulphate zinc
- From this list choose
- (i) a metal used to galvanise iron.
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- (ii) a transition metal.
- (iii) a metal which is in Group IV of the periodic table.
- (iv) a substance which will release carbon dioxide when an acid is
added.
- (v) a metal which is used to make aircraft bodies. [5]
- 3. J02/2/2. Candle sticks are often made of brass.
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- (i) Name an element from this table which is a transition element.
- Use the periodic table to help you. [1]
- (ii) Which element in the table is most likely to show non-metallic
properties. [1]
- (iii) Calculate the percentage of copper in this brass. [1]
- (b) Suggest why an alloy of copper and zinc is used to make
candlesticks rather than pure copper. [1]
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- (c) Gilding metal is a type of brass, which contains 90% copper and 10%
zinc. Which one of the following diagrams most accurately represents
this alloy. Put a ring around the correct answer.
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- (d) Brass ornaments tarnish after a time because the copper in them is
gradually oxidized to copper(II) oxide.
- (i) Complete the symbol equation for this reaction.
- 2Cu + …… ® 2CuO [1]
- (ii) Brass ornaments which have been tarnished can be cleaned with a
dilute solution of hydrochloric acid. The copper(II) oxide reacts with
the hydrochloric acid. Complete the word equation for this reaction.
- Copper(II) oxide + hydrochloric acid ® [2]
- (iii) Explain why copper(II) oxide is behaving as a basic oxide in
this reaction. [1]
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- 4. N01/2/2. The table shows some properties of five substances, A, B, C,
D and E.
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- (c) Which one of the substances A to E has the lowest melting point?
[1]
- (d) (i) Which one of the substances A to E is a gas at room
temperature? [1]
- (ii) Describe the arrangement and movement of the particles in a gas.
- (e) Two of the substances in the table are compounds. Explain what is
meant by the term compound. [2]
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- 5. J03/2/6 (e) Copper is alloyed with tin to make bronze.
- (i) State what is meant by the term alloy.
- (ii) Suggest why metals are often used in the form of alloys. [2]
- 6. N02/2/5 (e) Iron can be converted into steel, which is more resistant
to corrosion.
- (i) Describe briefly how iron is converted into steel. [2]
- (ii) State one use of mild steel. [1]
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- (f) In some conditions, steel corrodes more quickly than in others. The
graphs show the rate of corrosion of a particular type of steel under
different controlled conditions.
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- (i) How does pH affect the rate of corrosion? [1]
- (ii) How does temperature affect the rate of corrosion? [1]
- Explain this in terms of moving particles. [2]
- (iii) The presence of acidic gases in the air may increase the rate of
corrosion. State the name and source of one acidic gas found in the air
as a result of pollution.
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- 7. J04/3/5. (a) Copper has the structure of a typical metal. It has a
lattice of positive ions and a “sea” of mobile electrons. The lattice
can accommodate ions of a different metal.
- Give a different use of copper that depends on each of the following.
- (i) the ability of the ions in the lattice to move past each other
[1]
- (ii) the presence of mobile electrons [1]
- (iii) the ability to accommodate ions of a different metal in the
lattice [1]
- 8. N03/3/3 (b) A major use of zinc is to make diecasting alloys. These
contain about 4% of aluminium and they are stronger and less malleable
than pure zinc.
- (i) Give one other large scale use of zinc. [1]
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- (ii) Describe the structure of a typical metal, such as zinc, and
explain why it is malleable. [3]
- (iii) Suggest why the introduction of a different metallic atom into
the structure makes the alloy stronger than the pure metal. [2]
- (c) A solution of an impure zinc ore contained zinc, lead and silver(I)
ions. The addition of zinc dust will displace both lead and silver.
- (i) Write an ionic equation for the reaction between zinc atoms and
silver(I) ions. [2]
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- 9. J03/3/1 (d) Stainless steel is an alloy of iron. It contains iron,
other metals and about 0.5% of carbon.
- (i) State a use of stainless steel.
- (ii) Name a metal, other than iron, in stainless steel.
- (iii) The iron from the blast furnace is impure. It contains about 5%
of carbon and other impurities, such as silicon and phosphorus.
Describe how the percentage of carbon is reduced and the other
impurities are removed. [6]
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- 10. N02/3/4. For over 5000 years copper has been obtained by the
reduction of its ores. More recently the metal has been purified by
electrolysis.
- (a) Copper is used to make alloys.
- (i) Give two other uses of copper. [2]
- (ii) Alloys have similar structures to pure metals. Give a labelled
diagram that shows the structure of a typical alloy, such as
brass. [3]
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- 11. J02/3/1.(c) One property of aluminium is that it resists corrosion
because it is covered with a layer of its oxide.
- (i) Give one use of the metal that depends on this property. [1]
- (ii) Give another use of the metal that depends on a different
property.
- 12. N01/3/4. (a) Zinc is made by reducing zinc oxide. In 1695 Homberg
obtained zinc from calamine, zinc carbonate. At present zinc is
extracted from the ore, zinc blende.
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- (i) Suggest a way of changing calamine into zinc oxide. [1]
- (ii) Describe how zinc is extracted from zinc blende. [3]
- (b) Zinc oxide is used to make aqueous zinc chloride. This can be used
to preserve wood. Describe how this solution could be made. [3]
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- (c) Zinc is used to make alloys.
- (i) Name an alloy that contains zinc. [1]
- (ii) What is the other metal in this alloy? [1]
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Notes