Tweed River High School

TWEED RIVER HIGH SCHOOL 2006 PRELIMINARY CHEMISTRY

Unit 2 Metals

Part 1 Metals have been extracted and used for many thousands of years.

 Outline and examine sone uses of different metals throughout history, including contemporary uses, as uncombined metals or as alloys. Metals such as _____, ______and ______can be found as almost pure metals. The ability to _____ and _____ these metals into different shapes and their scarcity made them valuable to early civilisations. Archaeological evidence suggests that humans first started to use metals around 14000 years ago. The use of metals can be divided into ages, such as the ‘______Age’, the ‘______Age’ and the ‘______Age’.

The use of Copper throughout history. Archaeological records suggest that copper was the first metal to be extracted from minerals and used by humans. This period is sometimes referred to as the ‘Copper Age, (5000-3000BC).

1 To extract copper from ores such as ______(CuCO3.Cu(OH)2) and ______(CuFeS2), moderately high temperatures and an abundant supply of carbon are required. For this reason copper was probably first discovered as deposits in the bottom of campfires.

The Decomposition of Copper Ores The green coloured malachite, copper hydroxy carbonate, decomposes on heating to form ______according to the equation:

CuCO3.Cu(OH)2  2CuO + CO2 + H2O

The black copper(II) oxide then reacts with ______, in the form of ______, to form copper metal and carbon dioxide according to the equation:

2CuO + C  2u + CO2

The extraction of copper from chalcopyrite requires the addition of

______(SiO2) in the form of sand. This is added to remove iron as ______(FeSiO3). The modern extraction process occurs over several stages, but the overall extraction can be represented by the equation:

2CuFeS2(s) + 5O2(g) + 2 SiO2(s)  2Cu(l) + 4SO2(g) + 2FeSiO3

Early Uses of Copper Early uses of copper were ornaments, tools, weapons and cooking implements, (copper has excellent ______conductivity). Egyptians had copper beads and uses copper pipes to convey water. One of the disadvantages of copper is that it is a fairly soft metal.

2 Bronze is an alloy of copper. A small amount of _____ is added to copper. This improves the ______of copper. The early use of this alloy is called the ‘Bronze Age’, (3000-1000BC). Bronze has many advantages over copper. It allows tools such as axes and knives to maintain a good cutting edge and to be resharpened. Bronze shields and armour have also been discovered.

Contemporary uses of Copper Contemporary uses of copper relate to its excellent ______and ______conductivity, resistance to corrosion and its ability to form a huge range of alloys. Copper is used in electrical wiring, appliances, motors, water pipes, tanks and hot water systems. More than one thousand alloys of copper have been made.

The Use of Iron Throughout History

Iron ore is usually in the form of ______, (Fe2O3). In early times Hematite was added to ______and placed in a furnace with air being pumped through the mixture via a bellows to produce a high temperature. The overall reaction is:

2Fe2O3 + 3C  4Fe + 3CO2

The metal is then heated to red heat and hammered to expel ______leaving ______iron. The Hittites are thought to be one of the first to extract iron about 1500BC. By 1000BC the ‘Iron Age’ had replaced the Bronze age. Around 500BC, the Chinese had developed the first blast furnaces that could produce molten iron. This iron could then be poured into casts to produce ______iron.

3 Pure iron is susceptible to ______. Most iron today is made into and alloy with ______. Carbon-steels were probably first made about 1000BC, but large scale production did not begin until the middle of the nineteenth century. There are many types of steel which are used in construction, cars appliances and machinery. Homework: In the space below, copy Table 7.1, p110, Chemistry Contexts 1.

4 Aluminium Because aluminium was extremely difficult to extract from its ore, it was not used extensively until the beginning of the twentieth century when a commercially viable method of extraction was developed, (in 1886). Aluminium has a _____ density and is resistant to ______, (as it forms and outer oxide layer). This gives it many applications; (List the applications below)

Aluminium can be strengthened by the addition of other metals such as ______. This results in its suitability for use in spacecraft, aircraft and boat construction.

Titanium Titanium was discovered in 1791, but was not isolated until 1910. Titanium is the ______most abundant element in the earths crust. It occurs naturally in the minerals ______and ______. Titanium is a lustrous solid, (similar in appearance to stainless steel), it melts at _____ temperatures, has a _____ density, great ______and is very corrosion resistant. Titanium is used in aircraft, spacecraft, missiles and jet engines. Titanium alloys are ______and are used for surgical implants such as artificial knee and hip joints.

5  Describe the use of common alloys including steel, brass and solder and explain how these relate to their properties.

Homework: Pick four alloys from table 7.2, page 113, Chemistry Contexts 1 and copy them into a table below.

Steel Carbon-steel: Changing the amount of carbon in steel changes the ______and ______of the steel produced. The properties of steel can be further changed by forging, rolling processes, annealing, quenching and tempering. Annealing involves heating the steel to moderate temperatures and allowing it to cool ______. This makes the metal softer and more ductile. Quenching involves heating to moderate temperatures, followed by ______cooling. This produces hard but brittle steel.

6 Tempering is when quenched metal is heated to ______temperatures and allowed to cool. This reduces brittleness without losing hardness. Homework: Pick four alloys of steel from table 7.3, page 114, Chemistry Contexts 1 and copy them into a table below.

Solder Solder is an alloy of ______and _____. It has a lower melting point than either of the pure metals. This property allows it to be used for ______metals. It is extensively used in the ______industry and plumbing.

Brass Brass is an alloy of ______and ______. Its resistance to corrosion allows it to be used when corrosion is a problem. It is used in fasteners, household fittings, statues and figurines.

7  Explain why energy input is necessary to extract a metal from its ore. This point will be dealt with as a classroom discussion. You are to make brief notes in the space below.

 Identify why there are more metals available for people to use now than there were 200 years ago. This point will be dealt with as a classroom discussion. You are to make brief notes in the space below.

 Analyse information to relate the chronology of the Bronze Age, the Iron Age and the modern era and possible future developments. Homework: Prepare a brief timeline of the ‘Ages’ commenting on how improvements in technology has evolved the discovery and use of different metals.