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C3 Chemicals in Our Lives – Risks & Benefits

C3 Chemicals in Our Lives – Risks & Benefits. Lesson 8: Making Alkalis. Objectives. MUST interpret data showing that the chlorination of drinking water improved public health SHOULD describe the possible health risks of chlorine in water

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C3 Chemicals in Our Lives – Risks & Benefits

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  1. C3 Chemicals in Our Lives – Risks & Benefits Lesson 8: Making Alkalis

  2. Objectives • MUSTinterpret data showing that the chlorination of drinking water improved public health • SHOULD describe the possible health risks of chlorine in water • COULD understand how people perceive risk and how governments assess risk

  3. KeyWords • You need to be able to define the following: • Disinfectant

  4. Textbook Answers 1) Overcrowded living conditions; drinking water contaminated by sewage. 2) Chlorine is a disinfectant; it kills microorganisms. 3) a) 26–28; b) 10–12 years 4) The probability of death fell; from about 26 in 100 000 (about 1 in 4000) to 4 in 100 000 (about 1 in 25 000); a fall of over 80%. 5) 0.05 ÷ 0.2 × 100 = 25% 6) People are probably more scared of things they do not understand or are unfamiliar with, such as DBPs in water; so they overestimate the risk compared with risks they are familiar with. 7) Chlorine is a corrosive, toxic gas and can cause a great deal of harm; it can react with substances in water to make harmful compounds; but it is present in such a small concentration in water that it is a very low risk; the risk from diseases is greater than the risk from DBPs.

  5. Worksheet Answers Activity 1 (Low demand) 1) Should mention the dangers of untreated water, the correct dose and the hazard of using the disinfectant. 2) Should note the reduction cases of waterborne diseases. Activity 2 (Standard demand) 1) a) 4000; b) 20 000; c) 7–8 per 100 000; d) 14 000–12 500; e) death rate fell by over 70%. 2) a) Accurate bar chart; b) 1 in 1250; c) reduced the risk of catching cholera to 1 in 20 000. d) Chlorine solution is a hazard; particularly if drunk undiluted (it has happened). 3) Work of UNICEF, Médecins sans Frontières etc. Activity 3 (High demand) 1) Risk of bladder cancer in USA is 1 in 6000; risk of cholera in Haiti 1 in 170 (and possibly higher); cancers have other causes; suggests that risk without chlorination is much greater than the risk of cancers with chlorine. 2) a) E.g. fear of flying; the MMR vaccine debacle; smokers who do not give up. b) People tend to over-estimate the risk of unfamiliar things and under-estimate familiar risks. c) Education; rules on advertising

  6. Practical Answers

  7. Practical Answers Part D 1) sodium carbonate + hydrochloric acid  sodium chloride + carbon dioxide + water 2) hydroxide + acid  salt + water; carbonate + acid  salt + carbon dioxide + water 3) a) potassium hydroxide + nitric acid  potassium nitrate + water b) sodium hydroxide + sulfuric acid  sodium sulfate + water c) sodium carbonate + sulfuric acid  sodium sulfate + carbon dioxide + water d) potassium carbonate + nitric acid  potassium nitrate + carbon dioxide + water e) calcium hydroxide + hydrochloric acid  calcium chloride + water

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