DP Chemistry: A.7 Environmental impact - plastics

A.7 Environmental impact - plastics

Written specifically for students to provide help and support for the IB Diploma chemistry programme this page provides full coverage of the syllabus content of Option A - sub topic A.7. It encourages you to think critically and provides many questions with full worked answers so that you can monitor and improve your knowledge and understanding.

Learning outcomes

After studying this topic you should be able to:

Understand:

  • Plastics do not degrade easily because they contain strong covalent bonds.
  • The burning of polyvinyl chloride releases dioxins, hydrogen chloride gas and incomplete hydrocarbon as combustion products.
  • Dioxins contain unsaturated six-member heterocyclic rings that include two oxygen atoms, usually in the 1- and 4- positions.
  • Chlorinated dioxins can cause hormone disruption, leading to damage to cells and genetic material.
  • The recycling of plastics requires more processing than other materials.
  • The methods used to recycle plastics are based on different resin types.

Apply your knowledge to:

  • Deduce the equation for any given combustion reaction.
  • Discuss why recycling polymers is an energy intensive process.
  • Discuss the environmental impact of using plastics.
  • Compare the structures of polychlorinated biphenyls (PCBs) and dioxins.
  • Discuss possible health concerns of using volatile plasticizers to produce polymers.
  • Distinguish possible Resin Identification Codes (RICs) of plastics from an IR spectrum.

Relationships & vocabulary

Nature of science

The development and use of plastics is a good example of how scientific research often proceeds with perceived benefits in mind. Only later do the risks and implications become more apparent.

International-mindedness

Although a Mobius strip, designed in 1960s, is used as the international symbol for recycle, reuse and reduce, global recognition of this symbol ranks well below other symbols. What factors influence the recognition of symbols?

How can the problem of plastic floating in the Pacific Ocean gyre (known as 'the Great Pacific Garbage Patch' or 'Pacific trash vortex') be addressed internationally?

Vocabulary

dioxinpolychlorinated benzodioxin (PCCD)polychlorinated biphenyl (PCB)
phthalate estersResin Identification Code (RIC)

Learning slides

You can use this slide gallery for learning or for reviewing concepts and information. It covers all the key points in the syllabus for this sub-topic.

  

Something to think about

Three highly relevant items for ‘Something to think about’ have already been included elsewhere. The harmful effects of low molecular mass phthalate esters are discussed in  A.5 Polymers, the effects of PCBs on the environment are discussed in B.6 Biochemistry & the environment and the effects of the dioxins used in the Vietnam War are discussed in the practical on the Hydrolysis of halogenoalkanes.

This ‘Something to think about’ focuses on the Great Pacific Garbage Patch, which is alluded to under International Mindedness. A quick search will reveal many articles written on this. One good one is by Ocean CleIB Docs (2) Teamp. Essentially the Great Pacific Garbage Patch consists of not one but two separate patches, one located off the coast of Japan and the other between Hawaii and California.

The two 'Garbage Patches' in the Pacific Ocean - image from sdca.wordpress.com

They are caused by ocean gyres. A gyre describes the system of circular currents in the ocean caused by a combination of the Earth’s wind patterns and forces due to the Earth’s rotation. In the centre of these gyres the sea is relatively calm so all the debris collects there. Most of this is plastic due to the fact that most plastics do not degrade at all readily in the environment. You can find many videos on this but one of the comments often attached to them is “if this garbage patch is so big why do you not actually show pictures of it?” The reason is that although the plastics do not decompose chemically they do break down physically into ever more smaller particles known as ‘microplastics’ many of which are too small to be seen with the naked eye. The videos tend to concentrate on the larger pieces of plastic found in the stomach of birds etc. but the microplastics are also extremely harmful particularly to plankton feeders. They also reduce the amount of sunlight penetrating below the ocean’s surface. Because the plastics ‘belong’ to no one country and the cost of cleaning up the ocean would be huge, currently very little is being done to solve the problem. The effect on marine wildlife is huge and the problem is continually increasing even though eventually some of the plastic does sink to the ocean floor.

Test your understanding of this topic

(Note that your teacher may have restricted your access to some or all of these questions and worked answers if they are going to use them as a class test or set them as an assignment.)

For ten 'quiz' questions (for quick testing of knowledge and understanding with the answers explained) see MC test: Environmental impact - plastics.

For short-answer questions see Environmental impact - plastics questions together with the worked answers on a separate page Environmental impact - plastics answers.

More resources

1. Dioxins, what they are and their possible health effects by IAQ Video Network.

  Dioxins and their health effects

2. A sobering account of the effects of Agent Orange 35 years after the end of the Vietnam War.

  The after effects of Agent Orange

3. PCBs, what they are, where they are found and the problems they cause by Paul Cochrane.

  PCBs

4. Boyan Slat proposes a radical clean-up solution to the Great Pacific Garbage Patch problem.

  Solving the Great Pacific Garbage Patch problem

5. A good resource for the infrared spectra of various plastics can be found at the site by DoITPoMS from the University of Cambridge. One of the most obvious things it shows is the difference between PTFE and all the other plastics as there is no absorption at about 3000 cm-1 in the IR spectrum, since PTFE contains no C-H bonds.

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