Outline and examine some uses of different metals through history, including contemporary uses, as uncombined metals or as alloys.

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Metals

  • Outline and examine some uses of different metals through history, including contemporary uses, as uncombined metals or as alloys.

Native metals- gold, silver, copper

6000 BC                Copper first use

3000BC-2500 BC        Bronze Age (90% Cu &10%Sn)

1000 BC                On Set of Iron Age (Weapons harder and more powerful)

AD 1856        Development of Bessemer converter meant Cast Iron could be turn to Steel

AD 1886                Production of Aluminium

Today                        A variety of metals and alloys are used for different purposes.

LOOK AT ESSAY FOR BRONZE AND IRON AGE!

  • Describe the use of common alloys including steel, brass and solder and explain how these relate to their properties.

An alloy is a homogenous mixture of a metal with one or more other elements, which has been developed for a given purpose.

For example:

  • Steel: iron straight from the blast surface contains many impurities. It is called pig iron and is 96% pure. Too brittle to use in industries therefore converted to steel. Oxygen passed to remove carbon and lime to remove other impurities. Nickel and chromium help steel to resist corrosion.

Uses- Buildings, cutlery, white goods (high tensile strength, economical, resists corrosion)

  • Brass: alloy of copper (70%) and tin (30%)

Uses- Ornaments, Door hinges, Musical Instruments (shiny, attractive, lustrous, does not erode quickly and durable)

  • Solder: alloy of lead (70%) and tin (30%).

Uses- glues, metals together (low melting point, adheres firmly to other metals when molten)

  • Explain why energy input is necessary to extract a metal from its ore

For nearly all metals a chemical reaction is used to extract the metal fro its ore. Chemical reactions are accompanied by either release or absorption of heat, a form of energy. For most metals the extraction reactions require the input of considerable amounts of heat.

Energy is needed to mine the ore and to purify or concentrate it. Energy is required to maintain the high temperatures needed to make the extraction reaction go, and energy is needed to purify the raw metal or to form it into useful alloys.

To extract a metal from its ore it is normally heated up and therefore needs an input of energy. This heat separates the different metals because of its melting point and boiling point.

To make a compound energy is given out, so when a compound is extracted energy needs to be put in.

  • Identify why there are more metals available for people to use now than there were 200 years ago

The discovery of numerous new metals can be seen as evidence, in relation to the developments in science and technology within the past two hundred years. The discovery of the periodic table of elements and the electronic structure of atoms, revolutionised previous concepts and isolated elements based of their properties. With this new knowledge scientists now had insight into how different elements functioned and developed new ways of recognising them. The advancement of technology paralleling these new ideas, also played a significant role. A classics example would be electricity. Electricity opened up doors for new and improved extraction processes and new ways of isolating elements (e.g. electrolysis), which enabled scientists like Davy to isolate sodium, potassium, calcium and strontium. Faraday’s principle of electromagnetic induction led to the development of the dynamo, this meant that electricity could be produced in sufficient quantities for the use in Hall-Heroult processes involving the electrolysis of molten aluminia and cryolite to produce aluminium. The development of advanced machinery sped up chemical processes, allowed more accurate results to be obtained and reduced the costs involved in the process; for example the use of open cut mining of low grade ores and the flotation process, led to lower extraction costs. The creation of heavy machinery, and improved knowledge on their properties and extraction methods, have enabled mining processes to run sufficiently, further, allowing better access to a variety of metals.

  • Describe observable changes when metals react with dilute acid, water and oxygen.

All metals should (expect copper, silver, gold, platinum) react with dilute HCL and H2SO4 to form hydrogen gas. Effervescence can be seen and the test tube starts to heat up, as it is an exothermic reaction. For reactive metals, bubbles of H2 gas are observed on the metals surface. The reactive metals will eventually dissolve in the excess acid to form solutions of the metal salt.

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Metal + acid  salt + hydrogen

Some metals react with water or steam but others do not. When reactions occur with water the products are hydrogen gas and the metal hydroxide. Bubbles of colorless gas form and the solution produced is clear.

Metal + water  metal hydroxide + hydrogen

Most metals react with oxygen to form oxides, the changes occur over a significantly long period of time. When they slowly react at room temperature they lose their shiny lustrous appearance. And some metals such as aluminium become coated with a dull layer of adhering oxide that ...

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