Topic 10 - Using resources

• Ceramics are non-metal solids with high melting points that aren't made from carbon-based compounds
• Glass, another ceramic, is generally transparent, can be moulded when hot, and can be brittle when thin
• Most glass made is soda-lime glass, produced by heating a mixture of limestone, sand, and sodium carbonate (soda) until it melts.
• Borosilicate glass, with a higher melting point than soda-lime glass, is made heating a mixture of sand and boron trioxide
• Composites are made of one material embedded in another. Fibres or fragments of a material (reinforcement) are surrounded by a matrix acting as a binder
• Polymers' properties depend on how they're made and what they're made from
• Clay is a soft material when dug out the ground but can be moulded into different shapes. Clay ceramics are formed by firing clay at high temperatures, where it hardens. Clays ability to be moulded when wet and then hardened makes it ideal for making pottery and bricks
• Fibre glass (a composite) consists of fibres of glass embedded in a matrix made of polymer (plastic). It has a low density (like plastic) but is very strong (like glass). It is used for things like skis, boats and surfboards
• Carbon fibre composites have a polymer matrix like fibreglass. The reinforcement is either made from long chains of carbon atoms bonded together (carbon fibre) or from carbon nanotubes. These composites are very strong and light so are used in aerospace and sports cars manufacturing
• Concrete (a composite) is made from aggregate (a mixture of sand and gravel) embedded in cement. It's very strong. This makes it ideal for use as building material, e.g. in skate parks
• wood is a natural composite of cellulose fibres held together by an organic polymer matrix
• The properties of poly(ethene) depend on the catalyst that was used and the reaction conditions (the temperature and pressure) that it was made under:

  • Low density (LD) poly(ethene) is made from ethene at a moderate temperature under high pressure. It's flexible and is used for bags and bottles
  • High density (HD) poly(ethene) is also made from ethene but at a lower temperature and pressure with a catalyst. It's more rigid and is used for water tanks and drain pipes
• The monomers that a polymer is made from determine the type of bonds that form between the polymer chains. These weak bonds between the different molecule chains determine the properties of the polymer
• • Thermosoftening polymers contain individual polymer chains entwined together with weak forces between the chains. You can melt these plastics and remould them
  • Thermosetting polymers contain monomers that can form cross-links between the polymer chains, holding the chains together in a solid structure. Unlike thermosoftening polymers, these polymers don't soften when they're heated. Thermosetting polymers are strong, hard and rigid
• Pure metals are often too soft for everyday use due to their regular structure, so alloys are made by adding another element to disrupt the structure and make them harder
• Bronze (Copper + Tin) is harder than copper and used for medals, decorative ornaments, and statues
• Brass (Copper + Zinc) is more malleable than bronze and used where lower friction is required, like in water taps and door fittings
• Ceramics include glass and clay ceramics such as porcelain and bricks. They're insulators of heat and electricity, brittle (they aren't very flexible and break easily) and stiff
• Polymers are insulators of heat and electricity, they can be flexible (they can be bent without breaking) and easily moulded. Polymers have many applications including in clothing and insulators in electrical items
• The properties of composites depends 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 (they can be drawn into wires), shiny and stiff. Metals have many uses, including in electrical wires, car body-work and cutlery
• Gold alloys (zinc/copper/silver)are used to make jewellery. Pure gold is very soft. Metals such as zinc, copper and silver are used to harden gold. Pure gold is described as 24 carat, so 18 carats means 18 out of 24 parts of the alloy are pure gold. In other words, 18 carat gold is 75% gold
• Aluminium alloys are used to make aircraft: Aluminium has a low density which is an important property in aircraft manufacture. But pure aluminium is too soft for making aeroplanes so it's alloyed with small amounts of other metals to make it stronger
• Alloys of iron called steels are often used instead of pure iron. Steels are made by adding small amounts of carbon and sometimes other metals to iron

  
• This is a good example question on properties of materials - read over it

  
• Corrosion is where metals react with substances in their environment and are gradually destroyed
• The word "rust" specifically refers to the corrosion of iron, not other metals
• 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 available to rust again. This means that, eventually, all the iron in an object corrodes away even if it wasn't initially at the surface
• Aluminium also corrodes (like iron) when exposed to air. Unlike iron objects, things made from aluminium aren't completely destroyed by corrosion. This is because the aluminium oxide that forms when aluminium corrodes doesn't flake away. In fact it forms a protective layer that sticks firmly to the aluminium below and stops any further reaction taking place
• Experiments show that both oxygen and water are necessary for iron to rust:

  • If you put an iron nail in a boiling tube with just water, it wont rust (the water is boiled to remove oxygen and oil is used to stop air getting in)
  • If you put an iron nail in a boiling tube with just air, it won't rust (put calcium chloride in to absorb any water from the air)
  • However, if you put an iron nail in a boiling tube with air and water, it will rust (half subducted).
• The mass of a rusty nail will increase as the iron atoms in the nail have now bonded to oxygen and water molecules, resulting in a compound that is heavier than iron alone.
• There are two main ways of preventing iron from rusting: using a barrier and the sacrificial method
• The barrier method to prevent rusting (to stop water and oxygen getting to the iron):

  • Painting/coating with plastic - ideal for big and small structures. It can be decorative too
  • Electroplating - this uses electrolysis to reduce metal ions onto an iron electrode. It can be used to coat the iron with a layer of a different metal that won't be corroded away
  • Oiling/greasing - this has to be used when moving parts are involved, like on bike chains
• The sacrificial method of preventing iron from rusting involves pacing a more reactive metal such as zinc or magnesium with the iron. Water and oxygen then react with the sacrificial metal instead of the iron
• Some protection techniques employ both a barrier method and a sacrificial method. For example:

  • An object can be galvanised by spraying it with a coating of zinc. The zinc is firstly protective but if it's scratched, the zinc around the site of the scratch works as a sacrificial method
• Iron rusts when in contact with both oxygen and water (which are present in air), forming hydrated iron(III) oxide:

  
• Natural resources come from the earth, sea, or air and form without human input. For example, cotton for clothing or oil for fuel
• Some natural products can be replaced by synthetic products or improved upon by man-made processes, for example, rubber is a natural product that can be extracted from the sap of a tree, however it can be replaced by man-made polymers in uses like tyres
• Agriculture provides conditions where natural resources can be enhanced for human needs, like the development of fertilisers to produce high crop yields