There is much media talk and public interest about environmental issues like climate change, renewables, air quality, plastics and pollution. There are school children marches. Penalties for diesel cars to discourage nitrogen dioxide and particulate emissions are being introduced, and, astonishingly, the Tesla electric car company’s market value at £40 billion has now overtaken Ford’s despite only achieving a fraction of Ford’s sales. The UK Government is phasing out petrol engine cars by 2040 in favour of electric. What can we say about the inclusion of these topics in Science GCSE? Well, firstly, there are lots of examples, and “environment” is one of the few certain, banker questions in the whole of the GCSE syllabus. Secondly, examiners are looking for proof that students understand some of the technical language involved. Let’s take a look in more detail.
Questions about the environment in general have become so popular in Chemistry, Biology and Physics papers, in both core and triple science alike, that I sometimes think you just have to mention “carbon dioxide” and you are half way to a pass ! Even if you are a climate change skeptic, suspend that view until after the GCSE’s! Certainly the payback on a relatively small amount of revision on a not-too-difficult subject is high since one or more questions will almost certainly feature – which cannot be said about all science topics. After last year’s “drunken rat” controversy, students tweeted that they had learned their CGP Biology guide religiously, yet so little of the syllabus cropped up.
1. All three of the sciences begin this topic with fossil fuels, which are mainly oil and derivatives like petrol, also coal and gas.
2. There are two separate consequences of fuel combustion. On the one hand, the generation of the greenhouse gas carbon dioxide as a natural but increasing product of combustion. Then on the other hand emissions of bi products such as sulphur dioxide and soot which cause pollution and smog.
Candidates should ensure they understand both the advantages of fossil fuels and derivatives (fairly cheap, easily available, engines designed for them) and disadvantages (may run out, greenhouse gas generation, pollution, scars on the landscape). Similar pro and con assessments should be learned for individual, different renewables.
The basic mechanics of global warming should be understood. Rays from the sun entering the earth’s atmosphere bounce off the surface , and we need this to happen to a certain extent to provide warmth yet prevent overheating; but increased CO2 concentrations in the earth’s atmosphere don’t allow enough long wavelength infrared radiation to escape, leading to a small but significant warming of the earth. (This is the way greenhouse glass works).
Students should be able to interpret graphs such as global temperatures rising on the y-axis – but note the typically narrowed scale – with time on the x-axis, especially since the industrial revolution. These show global average temperatures rising around 1 degree C to 14.5 degrees, which alongside CO2 atmospheric concentrations rising from 0.028 to 0.038 % seem to provide a link.
Now let us summarise what revision is needed in each of the three sciences in addition to the above, and the type of question likely to be asked. (More detail is available in my coaching card lesson plans). Each science begins with the basic assertions above, particularly the part played by carbon dioxide in global warming, then develops different angles.
Pupils should understand how fractional distillation of crude oil works, including generating products such as petrol and diesel fuels as described in this BBC video about Grangemouth refinery where I visited many times in my work.
Students should learn the basic word equations associated with combustion of fuels which are generally alkane hydrocarbons .
Hydrocarbon + oxygen –> carbon dioxide + water + energy released
and one example, for natural gas combustion.
CH4 + 2O2 → CO2 + 2H2O
And also the word equation for acid rain, which damages buildings and statues, especially limestone :
Sulphur Dioxide + Water -> Sulphuric Acid
Students should also know the formulae of Nitrogen Dioxides (NO and NO2) and also understand how incomplete combustion produces sooty carbon particles (turning bunsen burners yellow) and in extreme circumstances the poisonous carbon monoxide (CO). Methods of reducing emissions are important such as scrubbers at power stations and catalytic converters on cars.
(In a sense I am pleased to see nitrogen and sulphur oxides (called colloquially “NOX and SOX”) being given priority once more. As a performance analyst in BP in the 1990’s I collated the emissions data from BP Chemicals’ factories including NOX and SOX. When CO2 was suddenly elevated to a much higher importance, I always worried that focus on these polluters might be lost).
The alternative fuels of particular interest in Chemistry are ethanol, bio-fuels like bio-diesel, and hydrogen along of course with their pros and cons. A further branch to revise is the benefits of electric cars and the two main means of powering them namely re-chargable batteries and hydrogen fuels cells. At typical question would provide data for energy use, cost, mileage and ask you to “evaluate” the alternatives which means recommend the best with justification.
The cracking of alkanes to alkenes and subsequent polymerisation also features in this context both for the fossil fuel origin and the non biodegradable nature of plastics.
Another branch of pollution features in metals extraction and mining, with heavy metal dis-colouration of rivers a possible disadvantage as seen in this article about the Colorado river.
Exam Questions have ranged from simple (what type of reaction is burning fuel in oxygen?); to numeric (compare the parts per million figures for particulates, carbon dioxide, nitrogen dioxide for several types of fuel); to everyday experience (why do supermarkets charge for plastic bags?); to involved (describe how a fractional distillation column works).
For Physics pupils need to know more detail about individual energy sources both conventional and renewable. The energy transfer steps for several of these should be understood. So for power stations running on fossil fuels, the transfer is from chemical (in the fuel), to thermal (burning it), to kinetic (turbines and generators); to electrical (the grid).
Nuclear power involves a plentiful supply of uranium and plutonium but they are finite resources so counted as non-renewable. And of course though they have the advantage of being green in a sense – no carbon dioxide emissions – the disadvantages include waste disposal and impact of major break downs (albeit rare) like Chernobyl.
The major renewable sources to learn are: solar panels (see this video of solar powered city) and solar cells; wind turbines and wind farms; geothermal hot rocks; hydroelectric power; and tidal barriers. For each of these students should learn the energy transfer process, and advantages and disadvantages, perhaps two of each. For instance, for wind energy the transfer is from from kinetic wind energy to kinetic blade energy to electrical. The advantages include it’s renewable, and has zero carbon dioxide emissions and pollution; but it is not always available (when calm), the turbines can scar the landscape, and though costs are reducing they are expensive to build and maintain.
Typical questions have included: is global warming of 5 degrees C over the next 100 years a fact, a guess or a prediction?; why are copper pipes under a solar panel painted black?; calculate the cost of waste energy from a food processor and how it is manifested; why do chemical salts used to store solar energy need a high specific heat capacity?; explain the difference in actual versus maximum electrical output percentages for a variety of energy sources; give 2 advantages and disadvantages of running gas fired versus nuclear power stations; why are transformers used between power stations and the national grid?; and what is the payback time on a project costing £1000 yielding savings of £500 per year (answer : a 2 year payback).
Finally, although electric cars are not specifically on-syllabus, that won’t stop AQA or Edxcel throwing in a wildcard question like “compare the advantages and disadvantages of electric cars versus conventional petrol or diesel engine cars”. Answers should include reference to easy availability of petrol (difficult for electric chargers); petrol is from fossil fuel and so contributes to global warning (electric cars do not – though the charger itself has to be charged); petrol and especially diesel cause particulate, sulphur and nitrogen dioxide pollution whereas electric cars do not; and conventional cars currently have a higher mileage range than electric.(Note that a £300m electric taxi factory is opening in Coventry – truth is stranger than fiction as 3 years ago an A Level Business Studies question case study was built around just such a possibility, Even Business Studies is not immune from our topic ! )
Photosynthesis and the carbon cycle are highly relevant in this context. This is a must for Biology exams, not just for the environment question. The word equation for photosynthesis must be learned:
Carbon dioxide + water (with sunlight) –> glucose + oxygen
6CO2 + 6H2O light –> C6 H12 O6 + 6O2
(The reverse equation for respiration of course also is important)
The carbon cycle includes the absorption of carbon dioxide through photosynthesis in leaves, and the production of carbon dioxide through respiration and also decay of dead animals, which eat vegetation. This has been in balance until recently when from the industrial revolution onwards fossil fuel combustion is producing more carbon dioxide – only by a fraction but enough to mean an increase in the concentration of carbon dioxide in the atmosphere, which in turn links through to the so-called greenhouse effect and global warming.
In Biology, further emphases include the generation of another greenhouse gas methane through more intensive farming, and the reduction in CO2 adsorption through Amazon rain forest depletion, in tandem with the production of CO2 from burning those forests.
Fossil fuel pollution includes damage to leaves from acid rain because their waxy layer for mineral absorption is damaged, while health is affected by carbon monoxide because in red blood cells it binds more strongly to haemoglobin than oxygen.
Typical questions include; describe the main points of the carbon cycle and the role of photosynthesis; what can we do to slow global warming?; interpret a bar chart of billions of tonnes of carbon dioxide produced at each stage of the carbon cycle.
Environment as a subject is as near to a banker question as you can get, and one of the few where parents can easily help children, especially as GCSE age is just young enough for pupils to still accept parental advice! Further, you will hear almost daily on the news stories about this topic, whose science may well feature in GCSE and so a round table discussion could follow at dinner. The key points are to start with are fossil fuels, but distinguish between carbon dioxide emissions – said to cause global warming; and sulphur and nitrogen oxides, bi product polluters causing building damage and health issues. Then candidates should be able to explain the science and list some solutions for these problems. The examiners want balanced arguments, so be prepared to list both the pros and cons for conventional and renewable energy sources.