Why not set up a "Chemical inquiry"? Four or five groups can look at a chosen chemical or synthetic material; each group will need two advocates to research advantages and another two looking into the disadvantages. Use texts or websites. They then present to the judgejury (maybe the rest of the class). The task is made a little difficult by the need for someone (teacher?) to look into the notion of "risk", and perhaps draw on some statistics... about as likely as "winning the lottery" and so on. As an example, the use of flame-retardants in furniture saves an estimated pound;1.1 billion a year in the UK (DTI figures); or illustrate risk with a simple experiment (add a metal to acid and make a salt, explaining the chemical hazards, noting that the industry takes the risks for us in manufacturing materials like nylon, medicines). Those debating the issue for or against need to think about:
* What are the "chemicals " used for?
* What is the nature, or characteristics (properties) of the chemical?
* Are there alternative materials?
* What are the advantages of the synthetic materials?
* What are the disadvantages of using the chemicals?
* What hazard symbol should the chemical carry?
A good pupil-friendly website on risks including statistics and chemical info is at: http:www.uyseg.orgrisked