Chemistry - Physical Properties and Uses of Metals (AQA)
Copper has many uses, one of which is to make pipes for carrying water.

Chemistry - Physical Properties and Uses of Metals (AQA)

The various materials that are used in building is one of the topics covered in GCSE Science. This is the sixth of seven quizzes on that particular subject and it looks specifically at the different physical properties of metals and suitable uses that can be found for them.

It is hard to imagine life without metals. They are strong and can be bent, beaten and stretched into shape without breaking. They also conduct both heat and electricity. Some of the less reactive metals can be found 'native' but the majority are obtained as ores. Ores are naturally occurring rocks that provide an economic starting point for the manufacture of metals. Iron ore is used to make iron and steel. Some metals, for example copper, can be easily extracted whilst others are more difficult. Our metals come from the crust of the Earth and will one day run out - they are non-renewable.

Different metals have different properties and so are suitable for different tasks. The uses of metals are linked to both their chemical and their physical properties. Copper conducts electricity extremely well and is soft - therefore, one of the uses it is most suitable for is as electrical wires. Although it is soft, it is hard enough to be used for plumbing and is an improvement on the original material, lead, as it does not react with water. It is not used for the cables that carry the electricity of the national grid - aluminium is used for that purpose as it is much lighter than copper. Most metals expand and contract by large amounts as they become hotter and cooler which is why the cables used for the national grid are slack. If they were tight, in the winter, they would contract, stretch and become weakened.

An interesting use of the expansion and contraction of metals is in bimetallic strips. These rely on the fact that different metals and alloys expand and contract by different amounts. When pieces of the same length of two different types of metal are joined firmly together, when the strip is heated or cooled, it will bend towards the metal that expands the least. This makes it useful for devices such as thermostats. Bimetallic strips are also used to make some types of thermometer and can even be used in analogue clocks and watches to help to regulate them as temperatures change.

Take this quiz to see how well you understand the physical properties of metals and how these affect their possible use.

Which of the following is not a physical property of titanium?
Low density
Corrosion resistant
Conducts electricity
Very strong
Corrosion resistance is a chemical property
Why are the metals magnesium and titanium used to make alloys for aircraft frames?
They are light metals
They are heavy metals
They are transition metals
They are silver coloured metals
When they are alloyed with aluminium, they form light but extremely strong alloys
Why do metals conduct electricity?
They have ionic bonds
They have covalent bonds
They have free electrons
The layers of ions in a metal
Some of the atoms in a metal lose an electron from their outermost energy level (shell) and these are free to move through the structure. Electricity is a flow of electrons
Why can metals be bent and pulled into shape?
The atoms of metals are soft
The layers of metal ions are able to slide over and past each other
The ions of a metal are able to break free of each other
They are ionically bonded
We say metals are ductile (can be pulled into shape) and malleable (can be hammered or bent into shape)
House electrical systems require a good earthing system to make them safe. The earthing system carries electricity safely into the ground and causes the safety devices in the house to 'trip', preventing electric shocks. Electricians sometimes fix the earth wires of a domestic electrical system to copper pipes used for the plumbing. Why is this?
The water in the pipe conducts electricity to earth
Copper is a good conductor of electricity
The pipes will stay cool in the event of an electrical emergency
It is an easy thing to do and saves them the time and trouble of putting a proper system in place
Water pipes are buried in the ground. Copper is a very good electrical conductor. Putting the two together makes a good way of providing an earthing system for older houses in particular. In newer houses that use plastic for the plumbing, a different system is used
Aluminuim is not as good a conductor of electricity as copper so why is it used for making the electrical cables for the National Grid?
It is easier than copper to make it into wires
It doesn't expand or contract
It is silver coloured so birds and pilots can see and avoid the cables
The density of aluminium is less than that of copper
There are several reasons but one of the important ones is that cables carrying electricity in the National Grid need to be large and therefore will be heavy. Using a low density metal like aluminium keeps the weight down as far as possible
Tungsten is a transition metal that is used for making the filaments of some electric light bulbs. What is the most likely reason for this?
Tungsten has a high density
Tungsten has a high boiling point
Tungsten has a high melting point
Tungsten is very cheap
Tungsten isn't one of the metals that you are required to know about but the examiners will often throw in questions about materials that you don't know. They are testing to see if you can make logical choices using what you know about the physIcal properties of metals being linked to their uses
Many people who ride mountain bikes buy parts made from titanium alloys. Which of the following is not a practical reason for making this choice?
Titanium alloys are lightweight
Titanium alloys have a high melting point
Titanium alloys are durable
Titanium alloys are resistant to metal fatigue
Titanium alloys are particularly of interest to racing cyclists who need tough, reliable and lightweight parts for their bikes. The melting point is of no concern to them at all!
Steel corrodes but it is still the best metal for making car bodies. Why is this?
Steel is shiny and makes cars look good
Steel conducts electricity
Steel conducts heat well
Steel is strong and malleable
A car body needs to be able to protect the occupants and to be easy to shape
Which of the following metals would be suitable for making a hammer?
Cast iron
Cast iron is too brittle and would break, copper is too soft and titanium would be too expensive
You can find more about this topic by visiting BBC Bitesize - Metals and alloys - AQA

Author:  Kev Woodward

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