Metals and their uses Flashcards
Define an ore
A rock which has enough metal in it to make it economical to extract the metal
The economics of extraction may change over time
How are unreactive metals such as gold produced?
Most metals?
Found in the Earth pure
Found as compounds which need chemical reactions to extract the metal
How are metals less reactive than carbon extracted from their oxides?
How is iron extracted from its oxide?
Reduction with carbon (removing oxygen by reacting it with carbon to form CO2)
Reduced in a blast furnace to make iron
How are metals more reactive than carbon extracted (such as aluminium and titanium)?
Why is this not ideal?
Electrolysis of molten or dissolved compounds
Electrolysis uses large amounts of energy, and the processes consist of many stages, which makes it very expensive, making the metals themselves expensive to buy
How is copper extracted from copper-rich ores?
Why do we need to be able to extract copper from low-grade ores?
Heating the ores in a furnace (smelting), then purifying by electrolysis
Copper-rich ores are being depleted; traditional mining and extraction have major environmental impacts
Describe the process of phytomining
Plants absorb metal compounds, then the plants are burnt to produce ash containing metal compounds
Describe the process of bioleaching
Bacteria produce leachate solutions containing metal compounds
How can copper be obtained from solutions of copper salts?
Electrolysis or displacement reactions (such as using scrap iron)
(During electrolysis, positive (metal or ammonium) ions move to the negative electrode
Why should we recycle metals?
Extracting them uses limited resources
Extraction is expensive in terms of energy and effects on the environment
Define an alloy
A metal made up of a mixture of metals and/or carbon
Why does iron from the blast furnace have limited uses?
How is it used and why?
It contains 96% iron, and the 4% impurities make it brittle
Cast iron because it is quite strong in compression
How is most iron we produce used?
It is converted into steel by mixing it with carbon, and some steels contain other metals
How does the quantity of carbon in steel affect its properties?
Low-carbon steels are easily shaped, whereas high-carbon steels are hard
What is a stainless steel?
An alloy of iron, carbon and other metals such as nickel to make it resistant to corrosion
Why are pure copper, gold, iron and aluminium not very useful?
How are they made useful?
They are too soft for many uses
They are mixed with small amounts of similar metals to harden them, ready for everyday use
