As we have become more knowledgeable about our environment, we have also become aware of the effects that our activities have on it. Elements and compounds that we find useful can also cause damage to our environment in certain circumstances. We have to be aware that there may be an environmental cost for our use of chemicals.
1 The importance of the ozone layer has become apparent in recent years, and we often hear that it is being damaged and even destroyed. The damage is believed to be caused by a number of different pollutants. a) Where is the ozone layer to be found in the atmosphere? Why is it important? b) Draw up a list of compounds that are thought to contribute to the thinning of the ozone layer. What are these compounds used for? c) What is the formula of methyl bromide? Draw a simple diagram to show the arrangement of its atoms. d) List five uses of methyl bromide. e) How can soil be sterilised without using methyl bromide? f) Explain why the use of methyl bromide might have increased over the last 25 years. g) To which group of elements in the periodic table do bromine and chlorine belong? h) What do you think the term 'food miles'means? i) Suggest two reasons why food is tr avelling further before it reaches us. j) What implications does this have for our reserves of fossil fuels and for global pollution? k) Many foods need to be chilled or refrigerated during transport. Certain fruits and vegetables have to be sterilised, often using methyl bromide. Explain why these measures are necessary.
2 The ozone layer in the upper atmosphere is important for our survival, but the amount of ozone it contains appears to be decreasing. Meanwhile the amount of ozone present at ground level is increasing and this is thought to be dangerous. a) Why is low level ozone increasing? b) What is thought to be responsible for the formation of ground level ozone? c) Why is low level ozone thought to be dangerous? d) Which people are most at risk?e) What is meant by the term 'photochemical smog'? f) When and where is smog most likely to develop? g) Why were smogs or 'pea-soupers'common in London and other big cities from Victorian times up until the 1950s? h) Explain why a cheap and efficient public transport system would reduce the risk of smogs developing today. i) Would the use of catalytic converters on all cars relieve the problem of air pollution?
3 Many reports have suggested that pollution in the form of nitrogen oxides and ozone are responsible for the increase in the number of people who suffer from asthma. Other reports have suggested that asthma attacks and even heart attacks may be triggered by very small particles in the air we breathe. a) What is thought to be the main source of these particles? b) What are other possible sources? c) How large are these particles? d) Estimate how many of these particles you might breathe in one hour. Show clearly how you arrive at your answer and what assumptions (if any) you have made. e) From the information in the articles, is it possible to say whether cars with diesel engines are more 'environmentally friendly' than cars with petrol engines? f) What two explanations are offered for these small particles triggering heart attacks?
