Using Resources- Chemistry

• Humans use the Earth’s resources to provide warmth, shelter, food and transport.
• Natural resources, supplemented by agriculture, provide food, timber, clothing and fuels
• Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials.
• Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
• Metals, glass, building materials, clay ceramics and most plastics are produced from limited raw materials. Much of the energy for the processes comes from limited resources. Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts.
• Some products, such as glass bottles, can be reused. Glass bottles can be crushed and melted to make different glass products. Other products cannot be reused and so are recycled for a different use.
• Metals can be recycled by melting and recasting or reforming into different products. The amount of separation required for recycling depends on the material and the properties required of the final product. For example, some scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore.
• Rusting is an example of corrosion. Both air and water are necessary for iron to rust.
• Corrosion can be prevented by applying a coating that acts as a barrier, such as greasing, painting or electroplating.
• Some coatings are reactive and contain a more reactive metal to provide sacrificial protection, eg zinc is used to galvanise iron.
• Most of the glass we use is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone
• Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than soda-lime glass.
• Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating in a furnace.
• Composites are when one material is embedded in another. Fibres/ fragments knows as reinforcements are surrounded by a matrix- binder. Properties depend on the properties of the materials used
• Fibre glass is when fibres of glass are embedded in a matrix of plastic. Low density and very strong. Example of a composite
• Carbon fibre- reinforcements are from carbon atoms in a long chain bonded together or carbon nanotubes. Example of a composite
• Concrete is an aggregate in cement. Strong. Example of a composite
• Wood is when cellulose fibres are held together by organic polymer matrix. Example of a composite
• iron needs both oxygen and water to rust
• rusting can be prevented with paint, galvanising (coating iron with zinc) and passivation (creating a protective layer)
• galvanisation prevents rusting because it creates a barrier between the metal and oxygen in air
• iron + water + oxygen -> rust
• 4Fe(s) + 3O2(g) +2H2O(g) -> 2Fe2O.H2O
• salt and other electrolytes increase the rate of rusting
• Aluminium does not corrode as it reacts with the oxygen in the air to create aluminium oxide. This creates a protective layer over the aluminium to prevent corrosion
• life cycle assessments


  getting the raw materials- energy required, manufacturing and packaging- waste products etc, using the product-amount of uses, product disposal- recyclable etc.
• some life cycle assessments can have an element of bias as it does not take into account actual values but processes instead
• potable water is water that has been treated or is naturally safe for humans to drink. chemists won't call it pure. important thing is that the level of dissolved substances is low and the pH is between 6.5 and 8.5
• rainwater is a type of freshwater. water from freshwater sources has to be treated to make it safe.
• process to make freshwater safe

  filtration- wire mesh screen- solids.

  sterilisation- kill any harmful bacteria and microbes. chlorine, ozone or UV
• in some dry countries desalination is used to treat water and make it safe. it is expensive and not practical for large quantities of water. see required practicals
• waste water comes from homes, agricultural systems and industries. it has to be treated to remove organic matter and kill harmful substances and microbes.
• sewage treatment


  -screened- remove large solids

  -stand in a settlement tank- sedimentation- heavier products move to bottom and lighter floats

  -effluent (lighter) is removed and treated by aerobic digestion- break down organic matter

  -sludge is removed releasing methane gas which could be used as an energy source.

  -waste water containing toxic substances- chemicals and UV etc
• sewage treatment requires more processes than fresh water and less energy than desalination.
• haver process is to produce ammonia which can be used in fertilisers
• formulated fertilisers are better than manure as they are widely available, dont smell and easier to use
• 3 main elements in a fertiliser is phosphorus, nitrogen and potassium. NPK
• potassium chloride and potassium sulphate can be mined and used as a source of potassium
• phosphate rock is mined but phosphate is insoluble.