Chemistry

4 April 2017

Iron is much harder than bronze. * Modern Age (1 CE – Present) – main metals are iron, aluminium and steel, which were used for pipes, buildings, transport and electrical cables. This is the age where technology of iron and steel improved. Around the 1880’s, there was a significant move towards new alloys and metals, including tungsten steel (cutting tools), manganese steels (railway lines and digging tools), silicon, chromium, nickel and vanadium. * Uses of metals Iron and steel – railways, bridges, roofing, motor car bodies, ships, fire hydrants, domestic appliances, heavy industrial machinery, pipes, nails.

They developed a table the illustrated the periodic law: properties of the elements vary periodically with their atomic weights. Mendeleev recognized that there were undiscovered elements and left gaps in his table. In 1913, Henry Mosely proposed a modified period law: properties of elements vary periodically with their atomic numbers. We now know that it is actually the electron configuration that determines the properties of elements.

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| Across a Period| Down a Group| Ionization energy| Increases| Decreases| Atomic radius| Decreases| Increases|

Melting point/boiling point| Increase in metals, and then decrease in gases| Increase| Valency| Increases| Stays the same according to group number| Electronegativity| Increases| Decreases| Reactivity | Decreases| Increases| Extraction of Metals * The ease of extraction depends on the reactivity of the element. The less reactive, the easier. * A mineral is any pure crystalline compound that occurs in the Earth’s crust, and is considered an ore if it is economically viable to extract a substance from the mineral. * The cost of metals is also important when choosing appropriate metals. * Less abundant ores are generally more expensive Some metals are expensive to extract from their ores (aluminium requires electrolysis, and is therefore more expensive then iron or copper) * Cost of transportation – ores found in remote areas require extensive, and sometimes specialized transport *

The yield is the amount of a product as a percentage of what is scientifically expected, and is important because it is critical when determining whether a mining or industrial venture is economically viable. * Eg. With a reaction of copper (I) sulfide with oxygen, the expected amount of copper is 2. 33 tonnes, but it is only 1. 97 tonnes. Therefore the yield is: 1. 972. 3 x 100 = 85% * The extraction of copper from sulfide ores (chalcopyrite – CuFeS2): * Concentration through froth flotation, where air is blown through tiny jets into a detergent solution, forming froth. The detergent means the sulfide particles are un-wettable and therefore will not be drawn into the bubbles. (2-25% Cu) * Heat the ore with sand, leaving Cu2S, producing the immiscible liquids of copper (I) sulfide, and the unwanted iron. This is known as smelting, where the substances are heated to high temperatures to form a molten material to extract a metal. 2CuFS2(s) + 5O2(g) > 2Cu(l) + 2FeO(s) + 4SO2(g)

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