Complete the sentences using present simple or present continuos: 1. look! ) the flowers in the garden! 2. more and more ) on the net nowadays 3. /wear) my t-shirts. i hate it! 4. ) the ball to neymar and ) a goal! 5. the train to ) at six 6. ) to australia next week? 7. ) at 100 c 8. excuse me, coat/belong) to you? 9. ) of moving house. i don't like this neighborhood 10. he ) to his emails immediately 11. ) that consumerism is like a disease: people cannot resist buying useless things. 12. ) sad, maybe, because she broke up with her boyfriend yesterday 13. why isn't john at work? -) well today 14. ) the soup to see if it needs salt 15. /be) so rude? i just asked you a question! is that so bad? 16. yuk! your ) awful! open the window! 17. ) of moving to germany. my husband was offered a great job with high monthly salary. it's a very good oppartunity to pass up 18. now ) that we underestimated her. we should have believed more in her and supported her 19. /look) at? -there's a crazy man shouting in the street! 20. ryan ) in a new film that will be at the theatres soon 21. to bag/belong)? it's been here for ages! 22. ) fred tonight. we're going out for dinner 23. global ) worse as time goes by 24. /see) that man over there? he's the mayor 25. can you stop doing that? /shout) while i'm studying!
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:
Secondly, it is the global warming as well as the environmental pollution. Every day the climate of the planet is changing more and more, reserves of fresh water are depleted, the environment is being polluted. All this is the result of human's activities, and if we continue to do this, the death of humanity within a few generations is inevitable.
Poverty, famine and homelessness are the causes of death for many years. To date, the number of people suffering from hunger and malnutrition has reached 1 billion people. It creates a serious threat to the international security.
The last thing I would like to say is about endangered species of animals and plants. Their habitats are being destroyed. This is due to global warming, logging, fire, mining. To sum up, it is necessary to make conclusions about the global problems of extinction of organisms.