1. What restaurant in place you live do you recommend?
2. Why is it a good place?
3. What is your opinion about eating out?
4. What food do you prefer most: homemade or take-away?
5. What are the eating habits in your country?
6. Are there any eating rules in your family?
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.
Объяснение:
1.Морозный зимний воздух состоит из миллионов ледяных кристалликов или крошечных пластинок. Изредка они выстраиваются в особом порядке и на закате или восходе отражают солнечный свет. В результате появляются вертикальные столбы света — будто мощный прожектор светит в небо (или с неба, как считают поклонники НЛО). По тому же принципу световые столбы могут возникнуть и ночью, при отражении света луны, уличных фонарей и автомобильных фар.
2.Когда луна находится невысоко и близка к полнолунию, напротив нее идет дождь, а небо темное и безоблачное, может возникнуть лунная радуга. Комбинация условий непростая, поэтому в отличие от солнечной радуги лунная встречается нечасто. Как правило, в дождливых местах или рядом с гигантскими водопадами — например, на Гавайях, Кавказе, в Йосемитском национальном парке в Калифорнии.
Объяснение:
3.NASA объясняет, что на самом деле каждая радуга — круглая, а с земли мы видим только ее часть. И если взглянуть на радугу с высокой горы или самолета, то при правильных условиях ее можно увидеть целиком, всю окружность. Шах и мат, лепреконы!
4.Вторичные радуги вызваны двойным отражением солнечного света в каплях дождя», — скучно бубнит энциклопедия. Но мы-то знаем, что двойная радуга — это просто красота в квадрате. Любопытно, что во второй, менее яркой радуге, цвета идут в обратном порядке — от фазана к охотнику.