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| Question | Answer |
| Complete the sentences: The double bonds in alkenes can open up and join together to make ____________. The individual, small alkenes are called ____________. This is ___________ polymerisation. | The double bonds in alkenes can open up and join together to make POLYMERS. The individual, small alkenes are called MONOMERS. This is ADDITION polymerisation. |
| What is the notation for repeating units of a polymer? |
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| Polymers are very unreactive. Why might that be advantageous? | Food doesn't react with PTFE coating on pans Plastic windows don't rot Plastic crates can be left out in the rain Etc. |
| Polymers are very unreactive. Why might this be disadvantageous? | Most polymers aren't biodegradable, so they're really difficult to dispose of |
| What are the 3 ways by which plastics can be disposed? | Burying waste plastic Recycling plastics Burning waste plastic |
| Where are waste plastics usually buried? | In landfills |
| Burying waste plastic in landfills is generally used when the plastic is... | Difficult to separate from other waste Not in sufficient quantities to make separation financially worthwhile Too difficult technically to recycle |
| What are the disadvantages of burying waste plastic in landfills? | The amount of waste we generate is becoming more and more of a problem, and the amount of free space for landfills is decreasing. Therefore, there is a need to reduce landfill as much as possible |
| Why should we recycle plastics? | Because many plastics are made from non-renewable oil fractions, it makes sense to recycle plastics as much as possible |
| Describe two ways in which plastics can be recycled | After sorting into different types, plastics can be: Melted and remoulded Cracked into monomers which can be used as an organic feedstock to make more plastics or other chemicals |
| What are the advantages of burning waste plastic? | The heat can be used to generate electricity |
| What are the disadvantages of burning waste plastic? | Toxic gases may be produced |
| How can the process of burning waste plastic be controlled to reduce toxic gases? | Waste gases from the combustion are passed through scrubbers which can neutralise gases (e.g. HCl) by allowing them to react with a base |
| What can biodegradable polymers be made out from? | Starch (from maize and other plants) The hydrocarbon isoprene (2-methyl-1,3-butadiene) |
| What are the advantages of using renewable raw materials? | Renewable raw materials aren't going to run out like oil. When polymers biodegrade, CO₂ is produced. If your polymer is plant-based, then the CO₂ released is the same CO₂ absorbed by the plant when it grew. BUT! With an oil-based biodegradable polymer, carbon is transferred from the oil to the atmosphere. Over their 'lifetime' some plant-based polymers save energy compared to oil-based plastics |
| What are the disadvantages of using renewable raw materials? | Whatever raw materials you use, at the moment the energy for making polymers usually come from fossil fuels. Biodegradable polymers still need the right conditions before they'll decompose, therefore you'll need to collect and separate the biodegradable from the non-biodegradable. At the moment, they're more expensive than oil-based equivalents |
| Describe the use of polyethene with starch grains | Plastic sheeting used to protect plants from the frost can be made from polyethene with starch grains embedded in it Over time, the starch is broken down by microorganisms and the remaining polyethene crumbles into dust. There is no need to collect and dispose of the old sheeting. |
| What other things could scientists to make processes involving polymers more environmentally-friendly? | Continuing to develop photodegradable polymers Developing better techniques for cracking polymers so that recycling becomes more efficient Finding new ways of making polymers from plant-based substances to reduce the use of finite raw materials Using processes with higher atom economy to reduce waste Developing new, more efficient ways of sorting and recycling polymers |
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