Syllabus section 5
Topic A closer look at electrode reactions
40-minute periods
Resources in Coursebook
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Section 4.6
Resources in Workbook
Resources on this CD-ROM Worksheet 4.4 A colourful electrolysis – demonstration
Activity 4.3 The electrolysis of concentrated sodium chloride solution Activity 4.4 Electroplating copper with nickel Activity 4.5 Electrolysis of copper(ii) sulfate solution Questions 4.15 to 4.16 EOCQ 6
Topic 1
Chemical reactions and equations
Coursebook section 4.1 (pp. 89–91)
Teaching ideas This is an introduction to the idea of chemical change – new substances being made – in contrast to a physical change. ◆
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The focus of this introductory session is simply the key aspect of chemical reactions: namely, that new substance(s) are formed. The distinction is with physical changes where, no matter how spectacular, the substances involved remain unchanged. It is possible to move on from this first point to begin to discuss the idea that atoms are simply ‘changing partners’ in a chemical reaction – old arrangements are being broken down and new combinations established.
Common misunderstandings and misconceptions There are few misconceptions here, although particular examples may be misinterpreted and need explanation.
Homework ideas ◆ ◆ ◆ ◆
Worksheet 4.1 Recognising chemical reactions Exercise 4.1 Key chemical reactions Coursebook questions 4.1 to 4.3 and End-of-chapter question 1 are useful in this context. Worksheet 4.6 Chemical mnemonics gives some useful ways of remembering key ideas.
Topic 2
Equations for chemical reactions
Coursebook section 4.2 (pp. 91–94)
Teaching ideas Introduce the concept of the law of conservation of mass – in a reaction atoms are simply changing the way in which they are combined – balancing equations. An equation is presented as a summary of a chemical change. ◆
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The aim here is to introduce the two forms of equation that students will encounter on this course. Both build on the key ideas introduced earlier. Word equations stem from the idea of the elements/compounds present in a reaction mixture recombining to form new substances. Balanced chemical equations develop this further in that the elements present and their recombination are clearly evident in the formulae involved. The concept of balancing stems from the need to account for all of the atoms involved. Diagrams and/or molecular models can helpfully be used to visualise the changes taking place. The approach that seems most successful here is that of progressive repetition, with the examples involved developing in complexity with time. The terminology of reactants and products also needs to be introduced, but that is straightforward compared with some of the more complex examples of balancing. Original material © Cambridge University Press 2014
© Cambridge University Press 2014 IGCSE Chemistry
Teaching ideas: Chapter 4
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