19 Questions
Why are alloys harder than pure metals?
Alloys have different sized ions that disrupt the regular arrangement, preventing layers from sliding easily.
Which metals are commonly used in gold jewellery alloys?
Silver, copper, and zinc
What property of ions in pure metals makes them softer?
Regular arrangement of same size ions
How do different sized ions in alloys affect the layers?
Disrupt the regular arrangement and prevent sliding
What makes the ions in alloys different from those in pure metals?
Different in size
Why can layers slide easily over each other in pure metals?
Regular arrangement of same size ions
What is the process used to extract iron from its ore?
Reduction
Which metal is extracted by electrolysis instead of carbon reduction due to its reactivity?
Aluminium
In the extraction of aluminium, what is used as the positive electrode?
Carbon
What gas is produced during the extraction of iron from its ore using carbon?
Carbon dioxide (CO2)
Why are metals like aluminium extracted by electrolysis and not by reduction with carbon?
They are more reactive than carbon.
Which process involves some plants absorbing metal compounds through their roots and burning them to produce metal-containing ash?
Phytoextraction
What is the property of aluminium that makes it suitable for use in aircraft and overhead power cables?
Corrosion resistance
What is the main reason pure copper, gold, iron, and aluminium are not used in everyday objects?
They are too soft
Which type of steel is known for its resistance to corrosion and is commonly used for cutlery and sinks?
Stainless steel
What is the primary characteristic of high-carbon steel that makes it ideal for cutting tools?
Hardness
In the context of metal alloys, what is the function of mixing small amounts of other metals with pure metals like copper and gold?
To improve hardness for everyday use
What property of iron from the blast furnace makes it unsuitable for most uses?
Brittleness
Which metal extraction method involves bacteria that absorb metal compounds and produce solutions containing the metals?
'Bacterial extraction'
Study Notes
Metal Extraction
- Metals that react with carbon can be extracted by electrolysis.
- Alternative methods of metal extraction include phytoextraction and bacterial extraction.
Phytoextraction
- Some plants absorb metal compounds through their roots and concentrate them.
- These plants can be burned to produce an ash containing the metal compounds.
Bacterial Extraction
- Some bacteria absorb metal compounds and produce solutions called leachates containing the metals.
Metal Properties and Uses
- Aluminium: low density, corrosion-resistant, used for aircraft, trains, overhead power cables, saucepans, and cooking foil.
- Copper: soft, good conductor of electricity, doesn't react with water, used for electrical wiring and plumbing.
- Iron: hard but too brittle, converted to steel, pure iron is too soft for many uses.
- Steel:
- Low-carbon steel (0.25% carbon): easily shaped, used for car body panels.
- High-carbon steel (2.5% carbon): hard, used for cutting tools.
- Stainless steel (chromium and nickel): resistant to corrosion, used for cutlery and sinks.
Alloys
- An alloy is a mixture of a metal and one or more elements, usually other metals or carbon.
- Most metals in everyday uses are alloys.
- Alloys are harder than pure metals because they have different-sized ions that disrupt the regular arrangement of layers.
Why Alloys are Harder
- In pure metals, ions are all the same size and in a regular arrangement, allowing them to slide over each other easily.
- In alloys, different-sized ions prevent layers from sliding over each other easily, making them harder.
Iron Extraction
- Iron is extracted through the reaction 2Fe2O3(s) + 3C(s) -> 4Fe(l) + 3CO2(g) in a blast furnace.
- This reaction is carried out at high temperatures.
Extraction by Electrolysis
- Metals that are more reactive than carbon, e.g. aluminium, are extracted by electrolysis of molten compounds.
- Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode).
Test your knowledge on alternative methods of extracting metals including electrolysis and phytoextraction. Learn about how plants absorb metal compounds and concentrate them in their tissues. No detailed knowledge on specific metal extraction processes is required for this quiz.
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