First and second conditionals 5 Write first or second conditional sentences. I / not mind / if you / be / a few minutes late (1st) I won't mind if you're a few minutes late. 1 I / be / in a band if I / live / in London (2nd) 2 what / you / buy / you / have / €250 /? (2nd) 3 where / you / wait / if it / be / raining / ? (1st) 4 I /be / happier if I / live / in a big city (2nd) 5 if you / meet / the

Plastics are non-metallic, synthetic, carbon-based materials. They can be moulded, shaped, or extruded into flexible sheets, films, or fibres. Plastics are synthetic polymers. Polymers consist of long-chain molecules made of large numbers of identical small molecules (monomers). The chemical nature of a plastic is defined by the monomer (repeating unit) that makes up the chain of the polymer. Polyethene is a polyolefin; its monomer unit is ethene (formerly called ethylene). Other categories are acrylics (such as polymethylmethacrylate), styrenes (such as polystyrene), vinys (such as polyvinyl chloride (PVC)), polyesters, polyurethanes, polyamides (such as nylons), polyethers, acetals, phenolics, cellulosics, and amino resins. The molecules can be either natural — like cellulose, wax, and natural rubber — or synthetic — in polyethene and nylon. In co-polymers, more than one monomer is used.The giant molecules of which polymers consist may be linear, branched, or cross-linked, depending on the plastic. Linear and branched molecules are thermoplastic (soften when heated), whereas cross-linked molecules are thermosetting (harden when heated).Most plastics are synthesized from organic chemicals or from natural gas or coal. Plastics are light-weight compared to metals and are good electrical insulators. The best insulators now are epoxy resins and teflon. Teflon or polytetrafluoroethene (PTFE) was first made in 1938 and was produced commercially in 1950.Plastics can be classified into several broad types.1. Thermoplastics soften on heating, then harden again when cooled. Thermoplastic molecules are also coiled and because of this they are flexible and easily stretched.Typical example of thermoplastics is polystyrene. Polystyrene resins are characterized by high resistance to chemical and mechanical stresses at low temperatures and by very low absorption of water. These properties make the polystyrenes especially suitable for radio-frequency insulation and for parts used at low temperatures in refrigerators and in airplanes. PET (polyethene terephthalate) is a transparent thermoplastic used for soft-drinks bottles. Thermoplastics are also viscoelastic, that is, they flow (creep) under stress. Examples are polythene, polystyrene andPVC.2. Thermosetting plastics (thermosets) do not soften when heated, and with strong heating they decompose. In most thermosets final cross-linking, which fixes the molecules, takes place after the plastic has already been formed.Thermosetting plastics have a higher density than thermoplastics. They are less flexible, more difficult to stretch, and are less subjected to creep. Examples of thermosetting plastics include urea-formaldehyde or polyurethane and epoxy resins, most polyesters, and phenolic polymers such as phenol-formaldehyde resin.3. Elastomers are similar to thermoplastics but have sufficient cross-linking between molecules to prevent stretching and creep.

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Not everyone knows how useful for our body is to ride a bicycle. most people spend hours these days in front of computer screens, which is not healthy at all. riding a bicycle has a number of benefits. first of all, it’s the time spent in the fresh air. it’s especially good when cycling is outside the city, for example, cross-country cycling or mountain biking. secondly, when we cycle we make our legs stronger, improve the overall endurance and respiratory system. thirdly, riding a bike one can save lots of money, which would be spent on city transportation of car fuel. besides, bicycles keep our environment in good ecological shape. many cities are now being supplied by special cycling lanes. as it’s been already mentioned, riding a bike has many health benefits, such as preventing vascular dystonia, increasing immunity, enriching blood with oxygen, reducing the risk of myopia, relieving stress, etc. one of the obvious things is the improved mood. many people note that after regular cycling they feel much better not only physically, but also morally. it is especially great if there is a friend who supports and enjoys riding as much as you. bicycle is highly recommended to those who want to lose weight. it is important to remember that cycling takes up lots of energy, so the balance can be restored by drinking plenty of water. in my opinion, the only danger connected with bicycles is the risk of frequent falls. to avoid them it’s good to check regularly the status of the brakes and tires.