10Using Different Materials 25/03/2017We use a variety of materials from a variety of different places:Cotton from plantsSilk from silkwormsWood and paper from treesThese are all “natural” materials – we can also use synthetic (man-made) ones like plastics – these are often made from materials from within the Earth like crude oil.
11Chemical formulae25/03/2017The chemical formulae of a molecule or compound is simply a way of showing the ratio of atoms in it. For example…NaCl= sodium chloride (NaCl)KI= potassium iodide (KI)OO= potassium nitrate (KNO3)KNO
12Chemical formulae Try drawing these: Water H2O Carbon dioxide CO2 25/03/2017Try drawing these:Water H2OCarbon dioxide CO2Calcium sulphate CaSO4Magnesium hydroxide Mg(OH)2
13Simple chemical reactions 25/03/2017MgOHClMagnesium oxide+Hydrochloric acidMagnesium chloride+WaterMgO+2HClMgCl2+H2OMgOCuSMagnesium+Copper sulphateCopper+Magnesium sulphateMg+CuSO4Cu+MgSO4Notice that the number of atoms on each side of the equation is the same!
14Hydrocarbons and crude oil 25/03/2017Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:Increasing lengthCHThese different “lengths” are called “_______” and most of them are used as _____. Some are used to make materials such as _______. Longer chains have higher _____ points.EthaneButaneCHWords – boiling, fractions, plastics, fuels
15Fractional distillation 25/03/2017Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:Fractions with low boiling points condense at the topFractions with high boiling points condense at the bottom
16Forces between molecules 25/03/2017Weak force of interaction hereLonger molecules = stronger force of attraction, leading to higher boiling points due to the molecules needing more energy to “pull” them away from each other.
17Polymers25/03/2017CHEtheneHere’s ethene. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics…Step 1: Break the double bondStep 2: Add the molecules together:This molecule is called POLYETHENE (i.e. polythene), and the process that made it is called POLYMERISATION
19Uses of addition polymers 25/03/2017Poly(ethene)Poly(propene)Poly(styrene)Poly(chloroethene), PVC
20Words – high, low, strong, weak, stretched, rigid Structure of Plastics25/03/20171) Some plastics have ____ intermolecular forces between each molecule – these have __ melting points and can be ________ easily2) Some plastics have _____ forces between each molecule. These have ____ melting points and are ____.Words – high, low, strong, weak, stretched, rigid
21Forces between molecules 25/03/2017As we’ve already said, longer molecules have stronger forces of attraction between them. This tends to lead to longer chain plastics being:StrongerStifferHarderMore difficult to melt (i.e. higher melting point)
22Modifying Plastics Polymers can be modified in a number of ways: 25/03/2017Polymers can be modified in a number of ways:Increasing the chain length...making it stronger2) Crosslinking...making it harder3) Plasticizing...making it softer and more flexible4) Packing more closely (a crystalline polymer)...making it stronger and more dense
24Nanotechnology25/03/2017Task: To find out what nanotechnology is and what it is used forWhat is nanotechnology?Define the terms nanoparticle and nanocompositeGives some examples of its usesDescribe some of the future uses of this technologyDescribe some of the ethical concerns over this technology
25Nanotechnology Definition: 25/03/2017Definition:Nanotechnology is a new branch of science that refers to structures built from a few hundred atoms and are 1-100nm big. They show different properties to the same materials in bulk, partly because they also have a large surface area to volume ratio and their properties could lead to new developments in computers, building materials etc.
26How nanoparticles are formed 25/03/2017Nanoparticles can be formed by a number of methods:They can occur naturally in sea sprayThey can also be formed during combustionOr they can be formed by grinding down materials
27Two examples of nanotechnology 25/03/2017The “Nano Carbon Pro” tennis racket uses nanoparticles to increase its strength.Silver nanoparticles can be used to give fibres antibacterial properties – look at what they do to e-coli bacteria:Normal e-coliE-coli affected by silver nanoparticles
28Nanoscience and health 25/03/2017Nanoparticles are obviously very small and, as we have said, have a large surface area to volume ratio. This makes them useful but can also make them dangerous. Nanoparticles could easily pass through a cell membrane:I’m going to die…How do these health concerns affect the development of nanotechnology?