C2 Quiz

Questão	Responda
What are the 6 main ways properties are measured?	Melting point, tensile strength (force needed to break a material when it is being stretched), compressive strength (force needed to crush a material when it is being squeezed), stiffness (force needed to bend a material) and density (mass of a given volume of a material)
What do strength and stiffness of a material depend on and what are they measured in?	Cross sectional area; measured in pascals (Pa)
What are the main properties of metals, ceramics and polymers?	Metals- shiny, malleable, conduct electricity; Ceramics (e.g. clay, grass, cement)- hard, strong; Polymers- large molecules, can be made into rubbers, plastics and fibres.
Define synthetic materials	Materials manufactured by chemical reactions which join simple chemicals together to make new materials (can be designed for a particular purpose)
Give two examples of synthetic materials replacing natural materials	Neoprene and silicone rubbers have replaced natural rubbers; Nylon replaced silk
Define crude oil	Also known as petroleum, a mixture of thousands of different compounds, many of which are hydrocarbons
What are alkanes and what is their general formula? (also the mnemonic)	Alkanes are a group of hydrocarbons, found in crude oil, with similar properties and the general formula C(n)H(2n+2). Monkeys, eat, peeled, bananas.
What is the general formula of alkenes and show a useful reaction with water.	C(n)H(2n); ethene + water = ethanol
What is formed when hydrocarbons combust?	Carbon dioxide and water
What is fractional distillation?	The process is used to separate the substances in crude oil. It works by heating crude oil to about 400 degrees which turns all the substances into gases. The gas passes into a tower called a fractional distillation column where it rises cools and condenses to liquid at their respective boiling points. At seven or 8 points the liquid is collected and piped off.
What are the products formed at each fraction?	Higher the boiling point, the longer the molecule. Bitumen used for roads and roofing 580 C +; up to 580 fuels for ships and central heating; up to 490 C lubricating oils, waxes and polishes; 260-330C diesel fuels; 175-260 jet fuel; 40-175 petrol and chemicals for synthesis; bottled gas 40C
What is a polymer and by which process are they made? Give an example.	Polymer is a long chain of molecules called monomers made through polymerisation. Polyethene is the simplest polymer and is made of carbon and hydrogen (ethene is the monomer)
How can we change the properties of a polymer? Give an example.	By adding a different kind of molecule to a hydrocarbon e.g. polytetrafluoroethene made from a monomer where all hydrogen atoms in ethene are replaced by fluorine atoms
What is PET?	Polyethylenetetrphalate has replaced glass for bottled water and soft drinks. It is a strong monomer that does not shatter and has a lower density (trucks can carry more of it) than glass
What impact does the proximity of polymer molecules have?	If they are closer more force will be needed to pull them apart so they have a higher boiling and melting point.
What does having branches make a polymer weaker?	They keep the molecules further apart
Give two ways (other than removing branches) you can increase strength between molecules	Having a more crystalline (regular) structure (although this can make them brittle) and having atoms such as nitrogen, fluorine, chlorine and oxygen in the chains.
How does having longer molecules impact upon a polymer? Give an example of polymer with long molecules.	A larger force is needed to separate them, for example UHMWPE used in artificial hop joints and chopping boards
What is a plasticiser?	Small molecules that fit between polymer molecules keeping them apart and weakening the forces between them, making materials softer and more flexible.
What is cross linking and how does this link to thermoplastics?	If cross links (thing that connect all polymer chains into one giant molecule) are present will not change shape when heated. Thermoplastic materials do change shape when heated whereas thermosetting (with cross links) do not. Cross-linked polymers are used for electric plugs and sockets because they can withstand high temperatures
How can a polymer be turned into a fibre?	By drawing it through a tiny hole, making the polymer molecules line up and become more crystalline. This gives the fibre higher tensile strength.
Define 'nanotechnology'	Technology between 1 and 100 nanometers in size (a thousandth of a millimetre)
Which nano-particles can be used as a catalyst?	Gold- as they have much larger surface area (i.e. a greater percentage is exposed) than normal particles for the reaction to take place on
How else could gold nano-particles be used?	In Roman times they were used to make a red colour as they scatter light in a different way to larger pieces of gold
How can silver nano-particles be used?	Kill bacteria that get into dirty socks so used to stop them from smelling, also used in wound dressings and in plastics for food containers and packaging
What are titanium oxide nano-particles used for?	Used in suncream making it transparent and allows visible light, but not UV, to pass through
Why would we mix nano-particles with other materials?	Makes the combined material (composite) stronger and more hard wearing
What are carbon nanotubes?	A roll of sheets of graphene, which are one atom thick, multi walled carbon nanotubes are a hundred times stronger than stainless steel.
Give two specific and one general concern about nanoparticles	Silver- could be leaked into sewage and the environment killing useful bacteria Carbon nanotubes- breathing in could cause diseases in the lungs General- can slip through pours in skin and be absorbed into the blood it is not know whether they are harmful due to a lack of research in this area

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	Criado por harry.vinall mais de 10 anos atrás