CFCs or chlorofluorocarbons are organic substances made from alkanes which have been halogenated. This means that one of the halogens, from group 7 of the periodic table, have been added to the molecule. This gives them useful properties. The halogens which are usually added are fluorine and chlorine; hence the name chlorofluorocarbons. CFCs were first made by Thomas Midgley Jr. in the 1920s. CFCs are used in a range of different applications, and they can be very helpful to us. So why are we phasing out their use? Well it turns out they are more dangerous than we ever thought.
Firstly, CFCs are very helpful to us. They are both non-toxic and non-flammable. This means that for humans, they are completely harmless. They will not explode when exposed to heat, and they will not kill us if we inhale them. So they sound great. Well, they have certainly been helpful in the production of many modern day applications. They are used in flame retardant clothing, as they help to prevent the materials from igniting. This is particularly important for children’s nightclothes. They are also used in aerosol sprays, because the vapours are not harmful to people or animals in any way. As well as aerosols the vapour forms are used in fire extinguishers, because they have a low boiling point, so the liquid in the storage cylinder can be converted to a gas when the CFCs hit the flames.
Our modern day life has been fuelled by CFCs, as they are used in circuit boards; which are found in pretty much all technology and electrical equipment. They prevent the circuit boards from igniting, which they might do if they were used for too long. They are also used in fridges, as refrigerants. Refrigerants are used to remove the heat from the fridge, in order to keep it at a cool temperature. With all these applications, it is difficult to see life without CFCs.
So if they are so useful – why do governments worldwide, along with most scientists want to see them gone. Well the reason is that the ozone causes damage that we do not see. They cause damage in places that we wouldn’t imagine it could.
The Earth’s atmosphere is a series of layers as you can see in the image to the right. In the stratosphere you will find a layer of gases called the ozone layer. This is a relatively thin layer (compared to the rest of the atmosphere), but it’s job is fundamental for life on earth.
In fact without it, no life would survive. The ozone layer is made up of O3 molecules of ozone. This is actually toxic to humans, but way up in the stratosphere it helps us to survive. What they do is they absorb most of the UV rays which arrive at the Earth’s atmosphere from the sun. The ozone breaks down as it absorbs the UV rays, but once the UV has been absorbed the ozone re-forms. This is a consistent reaction, since although the ozone is broken down, it forms again so overall the level of ozone is constant.
The problem with CFCs is, they go up into the stratosphere, where the UV rays present hit the CFCs, and causes them to break down too. However they form highly reactive chlorine free radicals. Free radicals are highly reactive particles which react with any particles nearby. Unluckily, it happens that these chlorine free radicals attack the ozone, breaking it down into oxygen, O2.
This may sound like a good thing – more oxygen means more air to breathe. However, we do not need any more oxygen, but we desperately need the ozone. The ozone is broken down very quickly, because one chlorine free radical reacts with one ozone, but it is not used up, since it acts as a catalyst for the break down of the ozone. Catalysts are not used up, so the chlorine can go on and react with thousands of ozone molecules, breaking them down more quickly than the ozone can form again.
This causes holes to form in the ozone layer, which is bad news for us. If more UV rays can penetrate through the ozone layer, it means more cases of skin cancer, cataracts and other UV related disorders. The image shown right is the hole over Antarctica. it seems confusing that the hole would form there, because no CFCs are released from the continent. However, the fact is that there is a catalyst in the Antarctic skies which helps to cause fasten the pace of ozone depletion even more.
In the Antarctic winter, the ozone is rebuilds itself and the hole shrinks. This is because there is 6 whole months of complete darkness. The sun never rises. However, when the 6 months of complete summer comes, this is where the problems begin. During the winter, icy stratospheric winds cause huge ice clouds to form. These clouds act as a catalyst, to make the breakdown of ozone happen faster. When the summer comes, so does the UV rays. The CFCs are already present, waiting for their chance to break down the ozone. When the UV rays come with the summer sunlight, there is 6 months of constant breakdown of ozone. During this time the hole grows again. This happens in a cycle, but overall, adding more CFCs into the atmosphere, will only make the depletion worse.
Therefore, in 1987, the Montreal Protocol was signed. This was an agreement that all countries would phase out the use of CFCs. It was first planned that developed nations like the USA, the UK and other such places would phase out the use of CFCs by 1995. However there have been a series of amendments to this date. Developing nations were given until 2010 to phase out their use of CFCS, however there were also amendments made to this number.
Alternatives have since been found. The most promising is HCFCS. These break down in the lower atmosphere, which means that they pose a much smaller risk to the ozone layer than the CFCS. However, they are still a form of CFC and they are still contributing to the depletion of the ozone layer. Therefore under the Montreal protocol, it has been agreed that these should also be phased out. HFCs have also be synthesised, but they are actually potent greenhouses gases. There are debates about who should decide the fate of HFCs. The Montreal Protocol should only deal with CFCs, so there are calls for the United Nations to take over the control of the use of HFCs.
However, no country has found a real safe alternative. Developed nations fear that safer alternatives may be expensive, and since they would like to pay as little as possible, this is a big concern. Will we have to give up our developed lifestyles, and be prepared to go without the fancy gadgets and modern developments that we have depended on for so long?
Fullick, Ann; McDuell Bob Edexcel AS chemistry ISBN 9781405896351 Pages 214 to 215