How are most metals found in the Earth?
Most metals are found as compounds. They have to be extracted by chemical reactions. The extraction method depends on its reactivity.
Unreactive metals such as gold are found in the Earth as metal.
What is a 'reduction' reaction?
A reduction reaction uses carbon to remove the oxygen from the oxide to produce the metal.
This only works in metals that are less reactive than carbon.
Why is most iron converted into steel rather than cast, wrought or pure?
Iron from a blast furnace (cast iron) is too brittle for many uses because of the impurities although it is hard, strong and does not rust.
Wrought iron is made by removing the impurities from cast iron and is almost pure iron. It is much softer than cast iron and used to make objects like gates.
Removing the impurities and carbon makes pure iron, which is too soft for many uses.
How is iron made?
Iron oxide (mainly found in the ore haematite) is reduced in a blast furnace to make iron.
What are steels?
Steels are alloys of iron (a mixture of iron with carbon and other elements).
An alloy is a mixture containing one or more metal.
Why is steel harder than wrought iron?
Steel consists of atoms of different sizes therefore the atoms cannot pack together to form a regular structure.
Because of this irregular structure the layers of atoms cannot slide over each other as they can in wrought iron, therefore steel is much harder.
Describe briefly some properties of low-carbon steel.
Low-carbon steels are soft and easy to shape.
Low-carbon steels are used for objects such as car bodies.
Describe briefly some properties of medium-carbon steel.
Medium-carbon steels are harder, stronger and less easy to shape as low-carbon.
Medium-carbon steels are used for objects such as hammers.
Describe briefly some properties of high-carbon steel.
High-carbon steels are hard, strong, brittle and hard to shape.
High-carbon steels are used for objects like razor blades.
Why is stainless steel a very widely used alloy, and why is this?
Stainless steel is extremely resistant to corrosion.
This is because it contains larger quantities of other metals- approx. 70% iron, 20% chromium and 10% nickel.
How do you prevent iron from rusting?
Rusting involves oxidation and is accelerated by salt water or by acid rain.
Iron can be prevented from rusting by completely removing it from contact with either oxygen or water (i.e: painting or coating iron in plastic or oil).
Define an ore.
An ore is a rock which contains enough metal to make it economically worthwhile to extract the metal.
Why does aluminium have to extracted by electrolysis?
It cannot be reduced using carbon because it's more reactive than carbon.
Why is aluminium and titanium so expensive?
Because extracting them involves many stages and requires large amounts of energy.
What is the main aluminium ore?
How does electrolysis of aluminium work?
-Dissolve aluminium oxide in cryolite.
-Positive aluminium ions attracted to negative electrode.
-Positive ions pick up electrons to form aluminium atoms.
-Negative oxide ions attracted to positive electrode.
-Negative ions lose electrons to form oxygen molecules.
-Oxygen reacts with carbon electrode to form CO2.
How can aluminium alloys be used?
Aluminium alloys combine high strength with low density.
It is useful for products like aeroplanes and mountain bikes.
It is also a good electrical conductor.
What is the main ore of titanium?
The main ore of titanium is rutile.
How is titanium extracted?
-The titanium oxide is converted to titanium chloride.
-The titanium chloride is reacted with sodium or magnesium.
How can titanium be used?
-Replacement hips and elbow joints.
How can copper-rich ores be extracted and why is this only used with copper-rich ores?
Smelting- heating the ore strongly in a furnace. This produces impure copper which can be purified by electrolysis.
Smelting and purifying copper require huge amounts of heating and electricity.
Scientists have developed ways of extracting coppers from low-grade ores which have less environmental impacts than smelting.
What is phytomining?
Phytomining uses plants to absorb copper compounds from the ground. The plants are burnt and produce ash from which the copper can be extracted.
What is bioleaching and what are some advantages and disadvantages with it?
Bioleaching uses bacteria to produce solutions containing copper compounds.
A- Simpler and cheaper than smelting.
A- Less damage to environment than smelting.
D- Very slow process.
Where are transition metals found on the periodic table?
The transition metals are found in the central block of the periodic table.
Describe some properties of transition metals.
Transition metals are good conductors of electricity and heat, have high melting points and a high density.
Many of them are strong, malleable and hard wearing.
Why and how do we use alloys?
Most of the metals we use are alloys. This is because pure iron, copper, gold and aluminium are soft and easily bent.
-Iron is made into steel.
-Gold used for jewellery is usually an alloy.
-Copper alloys include bronze and brass.
-Most aluminium used for buildings and aircraft are alloyed.
What are the advantages and disadvantages of using metals in construction?
A- Bent into shape.
A- Can be made into flexible wires.
A- Good electrical conductors.
D- Getting metals from ores causes pollution and uses up limited resources.
D- Metals are more expensive than materials such as concrete.
D- Iron and steel can rust.
Describe how cast iron is converted into steel (2 marks).
Tip: refer to oxygen and waste gases.
Carbon in cast iron reacts with oxygen to make CO2.
This removes the carbon, making the iron less brittle.
Aluminium and copper are good conductors of electricity.
State one property that makes aluminium more suitable than copper for overhead cables.
Less dense, therefore lighter.