Unit 10 - Using Resources

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Ceramics, Composites and Polymers

Ceramics are non-metal solids with high melting points that aren't made from carbon-based compounds. Clay is soft when dug up but when burned it hardens to form a clay ceramic when fired. Glass is also ceramic, it's transparent, can be moulded when hot and can be brittle when thin. Soda-lime glass is made by heating a mixture of limestone, sand and sodium carbonate until it melts.

Composites are made on one material embedded in another. Fibre and fragments of a material are surrounded by a matrix acting as a binder. The properties of a composite depend on the properties of the materials it's made from.

Two things can influence the properties of a polymer - how it's made and what it's made from. The monomers that a polymer is made from determine the type of bonds that form between the polymer chain. These weak bonds between the different molecule chains determine the properties of the polymer.

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Properties of Materials

Ceramics include glass and clay ceramics such as porcelain and bricks. They're insulators of heat and electricity, brittle and stiff. 

Polymers are insulators of heat and electricity, they can be flexible and easily moulded. Polymers have many applications including in clothing and insulators in electrical items.

The properties of composites depend on the matrix/binder and the reinforcement used to make them, so they have many different uses.

Metals are malleable, good conductors of heat and electricity, ductile, shiny and stiff. Metals have any uses, including in electrical wires, car body-work and cutlery.

Alloys are made by adding another element to the metal. This disrupts the structure of the metal, making alloys harder than pure metals. 

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Corrosion

Corrosion is where metals react with substances in their environment and are gradually worn away.

Corrosion only occurs on the surface of a material, where it's exposed to the air. Rust is a soft crumbly solid that soon flakes off to leave more iron avaliable to rust again. This means that eventually all the iron in an object corrodes away even if it's not initially at the surface. 

Word equation for rust:

           iron + oxygen + water ----> hydrated iron (III) oxide

There are two ways to prevent rusting:

  • One way is to coat the iron with a barrier to keep out the water and oxygen.
  • Another way is the sacrificial method, this involves placing a more reactive metal such as zinc or magnesium with the iron. Water and oxygen then react with the sacrificial metal instead of with the iron.
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Finite and Renewable Resources

Natural Resources form without human input, they include anything that comes from the earth, sea or air. Some of these natural products can be replaced by synthetic products or improved upon by man-made processes. Agriculture provides conditions where natural resources can be enhanced for our needs.

Renewable resources reform at a similar rate to, or faster than, we use them. Finite resources aren't formed quickly enough to be considered replaceable. Finite resources include fossil fuels and nuclear fuels . Metals and mierals found in ores in the earth are also non-renewable materials. After they've been extracted, many finite resources undergo man-made processes to provide fuels and materials necessary for modern life.

Many modern materials are made form raw, finite resources for example most plastics, metals and building materials. People have to balance the social, economic and environmental effects of extracting finite resources.

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Reuse and Recycling

Sustainable development is an approach to develpoment that takes into account of the needs of the present society while not damaging the lives of future generations. Not all resources are renewable so it's unsustainable to keep using them as well as extracting resources due to the amount of energy used and waste produced.

Copper is a finite resource:

  • Bioleaching is one way to to extract copper from a low-grade ore - bacteria are used to convert copper compounds, seperating out the copper from the ore in the process.
  • Phytomining - this involves growing plants in soil that contains copper.

Recycling metals often uses much less energy than is needed to mine and extract new metals, conserves the finite amount of each metal in the earth and cuts down on the amount of waste getting sent to landfill.

Glass recycling can help sustainability by reducing the amount of energy needed to make new glass products, and also the amount of waste created when used glass is thrown away. Glass bottles can often be reused without reshaping.

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Life Cycle Assessments

A Life Cycle Assessment (LCA) ooks at every stage of  product's life to assess the impact it would have on the environment:

  • Getting the raw materials - extracting raw materials needed for a product can damage the local enivronment, result in pollution due to the amount of energy needed. Raw materials ofen need to be processed to extract the desired materials and this often needs large amounts of energy.
  • Manfacture and Packaging - manufacturing products and their packaging can use a lot of energy resources and can also cause a lot of pollution. You also need to think about any waste products and how of dispose of them.
  • Using the product - using the product can damage the environment and how long a product is used for or how many uses it gets is also a factor.
  • Product Disposal - products are often disposed of in landfill sites, this takes up space and pollutes land and water, energy is required to transport the waste to landfill.

There are problems with LCAs:

  • LCAs can be biased beacuse producing an LCA is not an objective method as it takes into account the values of the person carrying out the assessment.
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Portable Water

Portable water is water that has been treated or is naturally sfe for humans to drink. Pure wate only contains H2O molecules whereas portable water can contain lots of other dissolved substances. The important thing is that the levels of dissolved salts aren't too high (p.H 6.5 - 8.5.)

Freshwater needs to be treated to make it safe before it can be used. Filtration - a wire mesh screens out large objects and then gravel and sand beds filter out any other solid bits. Sterilisatiion - the water is sterilised to kill any harmful bacteria or microbes, this can be done by bubbling chlorine gas through it or by using ozone or ultraviolet light.

Distillation can be used to desalinate sea water:

  • Test the pH of the solution using a pH meter, if it's too high or too low it will need neutarlising. Carry out a titration to do this, but use a pH meter to detect when the solution is neutral.
  • You should then test for sodium chloride; carry out a flame test for soduim ions (yellow flame) and for chlorine ions add dilute nitric acid and silver nitrate (white precipitate).
  • To distil the water, heat the water so it boils and evapourates, the salt will be left behind. The water will then condense back to liquid in the condensing tbe into a beaker. Retest for NaCl.
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Waste Water Treatment

Waste water comes from lots of different sources: washing-up, the Haber process and nutrient run-off from fields. All this waste water is carried through the drains to sewage. Sewage treatment happens in several stages:

  • Before being treated the sewage is screeened, this involves removing any large bits of material as well as any grit.
  • Then it stands in a settlement tank and undergos sedimentation - the heavier suspened solids sink to the bottom to produce sludge while the lighter effluent floats on the top.
  • The effluent in the settlement tank is removed and treated by biological aerobic digestion. This is when air through the water to encourage aerobic bacteria to break down any organic matter - including any microbes in the water.
  • The sludge from the bottom of the settlement tank is also removed and transferred into large tanks. Here it gets broken down by bacteria in a process called anaerobic digestion.
  • Anaerobic digestion breaks down the organic matter in the sludge, releasing methane gas in the process. The methane gas can be used as an energy source and the remaining digested waste can be used as a fertiliser.
  • For waste water containing toxic substances, additional stages of treatment may involve ading chemicals, UV radiation or using membranes.
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The Haber Process

The Haber process is used to make ammonia from hydrogen and nitrogen using the folllowing reaction:

     nitrogen + hydrogen           ammonia (+ heat)

  • the nitrogen is obtained easily from the air, which is 78% nitrogen
  • the hydrogen mainly comes from reacting methane with steam to form hydrogen and carbon dioxide
  • the reactant gases are passed over an iron catalyst, a high temperature and a high pressure are also used
  • the reaction is reversible, some of the ammonia produced converts back into hydrogen and nitrogen, it eventually reaches a dynamic equilibrium
  • the ammonia is formed as a gas, but as it cools in the condenser it liquefies and is removed, the unused hydrogen and nitrogen are recycled so nothig is wasted
  • the ammonia produced can then be used to make ammonium nitrate - a very nitrogen-rich fertiliser
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NPK Fertilisers

NPK fetilisers provide plants with the essential elements for growth:

  • fetilisers replace the missing elements or provide more of them, if plants don't get enough of these elements their growth and life processes are affected
  • formulated fertilisers are better as they're more widely avaliable, easier to use, don't smell and have just enough of each nutrient so more crops can be grown
  • fertilisers help to increase the crop yield as the crops grow faster and bigger
  • the 3 main elements in fertilisers are salts of nitrogen, potassium and phosphorus al in the right percentages

Ammonia can be reacted with oxygen and water in a series of reactions to make nitric acid. You can also react ammonia with acids to get ammonium salts. This reaction is carried out differently in industry to how it is in the lab:

  • In the industry, the reaction is carried out in giant vats at high concentrations resulting in a very exothermic reaction, the heat released is used to evapourate water form the mixture.
  • In the lab, the reaction is carried out on a much smaller scale by titration and crystillisation, the reactants are at a much lower concentration than in industry, so less heat is produced and is safer for a person to carry it out.
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