Grades 9 and 10 - Chemistry - High School - Chemistry - Physical Properties and Uses of Metals — Flashcards

Metals 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 - aluminum 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 analog clocks and watches to help to regulate them as temperatures change.