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Activity 1.2 Chemicals from seawater offers an opportunity to introduce some basic and standard practical techniques to the students (the need for this will depend on the prior experience of the students on earlier courses). It also links well with Worksheet 1.10 The acidification of the oceans.
Common misunderstandings and misconceptions These areas surrounding water availability, pollution and the water cycle are relatively straightforward and provide a way into discussing both the broad issues of the provision of clean drinking water to populations and the basic ideas of the changes of state involved in the water cycle. The chemistry of the oceans also gives an entry into discussing solubilty, both of solids and gases.
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Worksheet 1.10 The acidification of the oceans Exercise 1.3 Clean water is crucial
Topic 4 The Earth’s crust Coursebook section 1.4 (pp. 14–18)
Teaching ideas Illustrate the usefulness of mineral resources by discussing the usefulness of limestone. Introduce hydrogen as an alternative source of energy for the future, including hydrogen fuel cells ◆
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Limestone is a very useful mineral and it is used here as an example of a resource that can be quarried and processed to give useful products. The ‘limestone cycle’ is a useful introduction to some basic chemical ideas (Activity 1.3 Thermal decomposition of calcium carbonate). Activity 1.3 also offers an opportunity to introduce some basic and standard practical techniques to the students. The need for alternative energy sources has been touched on earlier and the ‘hydrogen economy’ offers one possible way ahead. The use of hydrogen to power cars raises some important introductory issues and again introduces some useful chemical ideas relating to exothermic reactions and the production of electrical energy from chemical reactions. Activity 1.4 Hydrogen power – communicating the benefits offers a good occasion to develop students’ research and presentation skills in an area where some will have keen interest. Activity 1.5 Using solar and hydrogen power offers a novel introduction to electrochemistry and the power that is available form the reaction between hydrogen and oxygen. The demonstration can be made quite spectacular, and also the difference between generating electricity and using electricity to split compounds can be introduced.
Common misunderstandings and misconceptions There are some cautions here in terms of the timing of the introduction of some aspects of the material. Both the treatment of limestone as a resource and hydrogen as a fuel are topics that will benefit from revisiting later in the course. It is suggested that any equations at the initial stages of these topics are restricted to word equations (depending, of course, on the prior experience of the students involved). Full chemical equations can be introduced when these topics are revisited. Note too that the syllabus specifically states that electrode equations for the hydrogen fuel cell are not required. One other area where care is needed is the terminology involved in the limestone cycle. This involves some relatively old-style English vocabulary and it is worth being careful to define the terms limestone, lime (quicklime) and limewater clearly.
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Use Activity 1.4 Hydrogen power – communicating the benefits as preparation for a class discussion/debate/ presentation. Exercise 1.5 Hydrogen as fuel Worksheet 1.3 Clean energy using hydrogen Worksheet 1.8 Fuel cells Original material © Cambridge University Press 2014
© Cambridge University Press 2014 IGCSE Chemistry
Teaching ideas: Chapter 1
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