C1- Metals and their Uses Flashcards
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).
Define alloy.
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?
Bauxite.
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 can titanium be used?
- Replacement hips and elbow joints.
- Aircraft.
- Pipes.
Where are transition metals found on the periodic table?
The transition metals are found in the central block of the periodic table.
