MYP 10
 
 


Unit 10.1: Metals and materials


Objectives

  • To understand that metals can be differentiated by reactivity
  • To understand that reactivity is related to position in the periodic table
  • To know that metals react by losing electrons
  • To know that loss of electrons is oxidation and that the opposite is reduction
  • To understand that water contains hydrogen ions by dissociation
  • To understand that acids are characterised by high concentrations of hydrogen ions
  • To know how iron is extracted by chemical reduction
  • To understand that metal extraction has social and environmental consequences
  • To understand that the atmosphere is a hostile environment for many metals

Unit 10.1 contents:


E-assessment 2016

The requirements of the forthcoming e-assessment, which will take place on Wednesday May 18th, 2016, means that the following topics must be covered during Unit 1:

Periodic Table: metals, non-metals and transition metals

  • redox reactions
  • reactivity series
  • extraction of metals
  • corrosion
  • electrochemical cells *

Metals are very useful in our everyday lives.

Ores are naturally occurring rocks that provide an economic starting point for the manufacture of metals. Iron ore is used to make iron and steel.

Copper can be easily extracted but copper-rich ores are becoming scarce so new methods of extracting copper are being developed.

Aluminium and titanium are useful metals but are expensive to produce.

Metals can be mixed together to make alloys.

Candidates should use their skills, knowledge and understanding to:

consider and evaluate the social, economic and environmental impacts of exploiting metal ores, of using metals and of recycling metals

Extracting metals

a) Ores contain enough metal to make it economical to extract the metal. The economics of extraction may change over time.

b) Ores are mined and may be concentrated before the metal is extracted and purified.

c) Unreactive metals such as gold are found in the Earth as the metal itself but most metals are found as compounds that require chemical reactions to extract the metal.

d) Metals that are less reactive than carbon can be extracted from their oxides by reduction with carbon, for example iron oxide is reduced in the blast furnace to make iron.

e) Metals that are more reactive than carbon, such as aluminium, are extracted by
electrolysis of molten compounds. The use of large amounts of energy in the extraction of these metals makes them expensive.

Knowledge of the details of industrial methods of electrolysis is not required

f) Copper can be extracted from copper-rich ores by heating the ores in a furnace (smelting). The copper can be purified by electrolysis. The supply of copper-rich ores is limited

  • ¦ copper is extracted from its ores by chemical processes that involve heat or electricity
  • ¦ copper-rich ores are being depleted and traditional mining and extraction have major environmental impacts.

g) New ways of extracting copper from low-grade ores are being researched to limit the environmental impact of traditional mining.

Copper can be extracted by phytomining, or by bioleaching.

Candidates should know and understand that:

  • ¦ phytomining uses plants to absorb metal compounds and that the plants are burned to produce ash that contains the metal compounds
  • ¦ bioleaching uses bacteria to produce leachate solutions that contain metal compounds.

h) Copper can be obtained from solutions of copper salts by electrolysis or by displacement using scrap iron.

Candidates should know that during electrolysis positive ions move towards the negative electrode. They do not need to describe this in terms of oxidation and reduction, or to understand half equations

i) Aluminium and titanium cannot be extracted from their oxides by reduction with carbon. Current methods of extraction are expensive because:

  • ¦ there are many stages in the processes
  • ¦ large amounts of energy are needed.

Candidates do not need to know the details of methods used to extract these metals, but should be able to comment on and evaluate information that is given about the chemical processes that can be used

j) We should recycle metals because extracting them uses limited resources and is expensive in terms of energy and effects on the environment.

Candidates are not required to know details of specific examples of recycling, but should understand the benefits of recycling in the general terms specified here

C1.3.2 Alloys

a) Iron from the blast furnace contains about 96 % iron. The impurities make it brittle and so it has limited uses.

Knowledge of uses of blast furnace iron is limited to blast furnace iron being used as cast iron because of its strength in compression

b) Most iron is converted into steels. Steels are alloys since they are mixtures of iron with carbon. Some steels contain other metals. Alloys can be designed to have properties for specific uses. Low-carbon steels are easily shaped, high-carbon steels are hard, and stainless steels are resistant to corrosion.

c) Most metals in everyday use are alloys. Pure copper, gold, iron and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make them harder for everyday use.

C1.3.3 Properties and uses of metals

a) The elements in the central block of the periodic table are known as transition metals. Like other metals they are good conductors of heat and electricity and can be bent or hammered into shape. They are useful as structural materials and for making things that must allow heat or electricity to pass through them easily.

Knowledge of the properties of specific transition metals other than those named in this unit is not required.

b) Copper has properties that make it useful for electrical wiring and plumbing.

Candidates should know and understand that copper:

  • ¦ is a good conductor of electricity and heat
  • ¦ can be bent but is hard enough to be used to make pipes or tanks
  • ¦ does not react with water

c) Low density and resistance to corrosion make aluminium and titanium useful metals.

a) Metals conduct heat and electricity because of the delocalised electrons in their structures.

Candidates should know that conduction depends on the ability of electrons to move throughout the metal.

b) The layers of atoms in metals are able to slide over each other and so metals can be bent and shaped.

c)Alloys are usually made from two or more different metals. The different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other and so make alloys harder than pure metals.

d) Shape memory alloys can return to their original shape after being deformed, eg Nitinol used in dental braces.


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