Preliminary Assessment Task 1

Jackie Huang – 11 Chemistry

Preliminary Assessment Task 1 – ‘Metals’ Part A: 1. Define the terms mineral and ore. A mineral is a naturally occurring inorganic solid, consisting of a crystalline structure, a definite chemical composition, and an ordered atomic arrangement. An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element(s). 2. Describe the relationship between the commercial prices of common metals, their actual abundances and relative costs of production. Factors which affect the price of metals include: - The abundance and location of their ores, generally less abundant metals will have a higher commercial price. The location also determines the cost of metals, if the mining zone was highly populated; damages will be made to the environment and increases the cost of production. -The amount of energy input into extracting the metal from the ore. If a lot of energy is needed to purify and extract the ore, the extraction cost and the metal will also be raised. Titanium is an example of an expensive metal because of the difficulty to extract it from its ore. 3. Explain why ores are non-renewable resources. Metal ores are non-renewable resources because they have been naturally formed since the formation of the Earth and there is no way of forming anymore of them. 4. Describe the separation processes, chemical reactions and energy considerations involved in the extraction of copper from one of its ores. The first step to extract the ore is to mine it. Many ores which contain copper are also filled with other minerals, which makes copper generally 1-5% of the ore. In Australia, the most common ore with copper are sulphides, such as chalcocite (CuFeS2). The ore is then crushed into a powder and minerals are concentrated into slurry which is usually about 15% copper. Float flotation is then used to purify the ore by blowing air (adding oxygen) into a detergent solution. The copper will be raised by the bubbles, then the surface which usually contains 25-30% copper, is skimmed off as the unwanted minerals sink to the bottom because they have been wetted by the solution. 2CuFeS2 (S) + 302 (g) -----> 2CuS(s) + FeO(s) + 2SO2 (g) To extract the copper, the concentration goes through pyrometallurgical methods (smelting and roasting), which requires energy input to sustain the temperature at which the process takes place. The concentrated ore is roasted in air (placed in a furnace), which oxidises the FeS to FeO but leaves the Cu2S unaffected. Smelting of the copper concentrate and extraction by heat, flux and addition of oxygen. Sulfur, iron and other undesirable elements are removed and the product is called blister copper, which is generally 98% pure. Cu2S (s) + O2 (g) ----> 2Cu (s) + SO2 (g)

Jackie Huang – 11 Chemistry To purify the ore, the copper is put through electrolysis, producing high purity copper. The copper is dissolved at the anodes and 2 of its electrons are travelled through the wires to, migrating it back to the cathodes, where the pure copper ions collect its 2 electrons.

At the anode: Cu(s) → Cu2+(aq) + 2eAt the cathode: Cu2+(aq) + 2e- → Cu(s) 5. Recount the steps taken to recycle aluminium. 1. Collect the used metals from factories, homes and shopping centres. 2. Transport the collected materials to a recycling plant, checked and separated. 3. The aluminium is taken to a furnace to melt the material. 4. Then cooled and made into thin sheets. 5. This is then made into commercial products such as cans and other packaging. 6. Justify the increased recycling of metals in our society and across the world. The recycling of metals in our society is a necessity. The increase of metal costs and the diminishing of the amount of metals are a clear problem. Recycling is used to replenish the metals supply for the world. It is also much cheaper to recycle than mine and purify ores for the metal. The non-renewable natural sources of metals are conserved, which counter the problem of the Earth running out of metals. Recycling also helps control pollution levels. By recycling, there is less waste disposal which is also beneficial. Therefore, increased recycling in our society is needed to maintain a sufficient amount of metals. 7. Discuss the importance of predicting yield in the identification, mining and extraction of commercial ore deposits. Without being able to predict the yield of an ore deposit there is no way to know if it will be a profitable commercial investment. Yield is the amount of profit a company will make after the difference of its total spent. Mining is a costly business; companies will need to determine its yield on an ore deposit to determine if they should mine there. This is essential as companies will invest money to set up equipment and infrastructure without having a good idea of what quantities they will mine. It also helps determine how long the life time of the ore deposit and how long it will last. Companies need this information to decide whether to invest into these areas. 8. Analyse information to compare the cost and energy expenditure involved in the extraction of aluminium from its ore and the recycling of aluminium. Aluminium is the third most abundant metal in the Earth’s crust, but is more expensive to extract it from its ore than iron. To extract it, a large amount of electricity is used for electrolysis which increases the cost. To extract it from its recycled scraps, only 5% of the energy needed from extracting it from its ore is used. This clearly shows the difference of energy and cost in extracting from its ore and from its recyclables.

Jackie Huang – 11 Chemistry 24/5/12 http://www.gcsescience.com/ex13.htm

23/5/12 http://www.chemguide.co.uk/inorganic/extraction/copper.html 23/5/12 https://sites.google.com/site/fullynotes/metals

23/5/12 http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/rocks_metals/4_metals _alloys1.shtml 22/5/12 http://www.oum.ox.ac.uk/thezone/minerals/define/index.htm 23/5/12 http://www.scribd.com/doc/45878585/8-3-Metals-Notes

Roland Smith – Conquering Chemistry: Preliminary Course

23/5/12 http://resources.schoolscience.co.uk/CDA/11-14/chemistry/copch32pg2.html 23/5/12 http://wwwchem.uwimona.edu.jm/courses/copper.html 24/5/12 http://resources.schoolscience.co.uk/CDA/14-16/cumining/copch2pg4.html