Chemistry 14, Using Earth's resources

Give two examples of natural products that are supplemented by agriculture and two which are replaced by synthetic products

-Chicken -Wheat (both in larger quantities due to agriculture organisation -Cotton is replaced by polyester in clothes and wood replaced by PVC in construction

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What is sustainable development?

Meeting the needs of the current generations without compromising the ability of future generations to meet their own needs

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What is potable water?

Water that is safe to drink. It has low levels of dissolved salts and microbes in so isn't pure water

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How do you get potable water from a source such as a river or lake?

-Passed through large object filter -Small sediment sinks out -Aluminium carbonate is added, clumps particles, more sediment sinks -Passed through sand to remove grit and mud -Treated with chlorine, ozone or UV to remove microbes -pH is checked

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What are the two methods of desalination? Briefly describe them

1. Distillation, salt is evaporated out, water condeses 2. Reverse osmosis (using membranes) Pressure is applied which forces the smaller water particles through the membrane but prevents the larger salt molecules from fitting through

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What are the issues with the methods of desalination?

Both of the processes require lots of energy, Distillation too heat the water and reverse osmosis for the pressure, which is expensive to create

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Describe the steps of sewage treatment (minus the sludge)

•Grit and large objects are removed by screening •Water is left and sediment settles out forming sludge •The watery liquid called effluent moves into the next tank •Effluent is aerobically digested and aerated then put back into rivers

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Describe how the sludge formed from waste water is treated

•It is digested anaerobically by microorganisms •It can be broken down to form biogas which is burnt for energy; either for the sewage plant or for electricity for the area •It can be further cleaned to form methane and pumped into the gas supply

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Give four ways in which copper can be extracted

-Smelting -Using sulphuric acid -Bioleaching -Phytomining

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Why are new methods for extracting metals becoming necessary?

Rich ores are being quickly used up and are not very available. Methods of extracting metals from low grade ores have had to be developed to make the most of the metals left. These new methods include bioleaching and phytomining

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Explain bioleaching

•Bioleaching involves using bacteria •When some bacteria are breaking down materials they absorb copper (or other metal) compounds which are then released as leachate that can be electrolysed or displaced to give the metal

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Explain phytomining

•Involves plants which absorb metal compounds in their roots •The metal collects in the plant and becomes concentrated •The plants are harvested and burnt producing ash containing the metal compound •A metal oxide forms that can be leached/displaced

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What is an LCA (life cycle assessment)?

It assesses the environmental impact of product in each of these stages: -Extracting and processing raw materials -Manufacturing and packaging -Use and reuse -Disposal -Transport and distribution are included at each stage

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What is an issue with LCA's

Not entirely objective as allocating numerical values to pollutant effects is not easily quantifiable so will be subjective

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Why do we need to reduce the use of earth's resources?

So that they don't run out but also because quarrying and mining cause environmental impacts such as noise, dust, visual pollution, destroying habitats and contaminating water with metal ores

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Chemistry 14, Using Earth's resources

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