2.1 Land versus water Mammals share a number of biological characteristics that mark them out as members of the class Mammalia. Many of these are adaptations to a life on land. For example: Mammals give birth to young at a relatively advanced stage of development and feed their young on milk. Most mammals have hair, or fur, covering part or all of the body. Mammals have a high metabolic rate and maintain a relatively high and constant body temp
7.4 Equilibrium positions and rates of reaction in this unit Section 7 showed that if a reaction is to occur at a particular temperature, two conditions must be fulfilled: its equilibrium constant must be sufficiently large, and its rate sufficiently great. We finish by pointing out how this crucial distinction between the equilibrium constant and the rate reveals itself in Figure 52. The f
7.3 Is the rate of reaction very slow? If the equilibrium position is very favourable, then the reason why Reaction 8.1 fails to occur at 525 °C must be that its rate is very slow. Usually, a reasonable response would be to increase the temperature yet further, but the structure and economy of the car gives us little scope to do this. The alternative is to use a catalyst, which leaves the equilibrium constant unchanged, while speeding the reaction up. Let us look at the changes that take place in the internal energy
7.1 Introduction So far, we have concentrated on the electronic and spatial structures of chemical substances, but we have not said much about chemical reactions. Now we turn to the question of why chemical reactions happen. To remind you of the basic ideas, we shall concentrate on one particular reaction which occurs in the modern motor car.
Table 2 shows typical percentages of the main constituents of the exhaust gas that emerges from a modern car engine. The two most dangerous pollutants are carbon
6.4 Summary of Section 6 Molecules have a three-dimensional shape. Bulky irregularities in the shape of a molecule around a reactive site can exclude a potential reactant. Such effects are described as steric. A sufficient refinement of the molecular shape in the region of the reactive site can make that site specific to just one particular reactant. Many enzymes operate in this way. The shapes of simple molecules can be predicted using valence-she
6.3.1 Refinements and difficulties In Section 6.2, we said that inter-axis repulsions vary in the order: non-bonded pair–non-bonded pair > non-bonded pair–bond pair > bond pair–bond pair There is evidence for this in the inter-bond angles in molecules. For example, in wat
6.1 Introduction Structural formulae of, for example, hexan-1-ol (Structure 6.1) and PF5 (Structure 5.13) merely tell us the immediate neighbours of any particular atom. They are two-dimensional drawings, which ignore the three-dimensional shapes of the molecules. But in studying the structures obtained by X-ray crystallography in Sectio
5.1 Molecular reactivity is concentrated at key sites Reactivity is not spread evenly over a molecule; it tends to be concentrated at particular sites. The consequences of this idea are apparent in the chemistry of many elements. However, in organic chemistry, the idea has proved so valuable that it receives specific recognition through the concept of the functional group. Structure 6.1 shows the abbreviated structural formula of hexan-1-ol, an alcohol. 4.5.4 Resonance structures Gaseous oxygen occurs as O2 molecules. But ultraviolet light or an electric discharge converts some of the oxygen to ozone (Box 6). This has the molecular formula O3. Many people know that gaseous ozone in the stratosphere protects us from harmful sola 4.5 More about covalent bonding So far, the valencies in Table 1 have just been numbers that we use to predict the formulae of compounds. But in the case of covalent substances they can tell us more. In particular, they can tell us how the atoms are linked together in the molecule. This information is obtained from a two-dimensional drawing of the structural form 2.2.4 Identifying the carbon heavyweights I've focused on two studies of the carbon footprint of UK individuals and households, but there are many others (e.g. WWF, 2006; Goodall, 2007 and Marshall, 2007a). 1.3.5 Corporate connections As I mentioned in Section 2, what was happening in the factories of overseas contractors was said to have appeared remote to most, if not all, the chief executive officers of the clothing multinationals in the 1980s. Overseas contractors were selected on the basis of market price, quality and reliability, not on whether forced or child labour happened to be employed to stitch the product together. However, all that changed in the early 1990s when the geographical ties between the big retailer 1.3.4 Bringing remote sweatshops within reach continued Another claim made by the movement is that we are all in some way connected to a market system which effectively allows sweatshops to exist in the first place. This is about more than targeting the big brand names and linking them directly to exploitation abroad; rather, it is about piecing together the global market machinery that ties the corporate buyer, the boardroom executive, the factory owner and the consumer into a system which establishes particular lines of responsibility (Ha 1.2.7 In praise of cheap offshore labour? Claims over the benefits of globalisation and the exploitation of cheap offshore labour generate strong feelings and, not surprisingly, divide opinion between those who favour the global marketplace and its detractors. The issue turns on whether the constant search for ever-cheaper manufacturing and service locations is seen as a good or a bad thing. It may appear odd, at first, to suggest that exploiting the poor of another country can, on any measure, be regarded as a good thing, but 1.2.5 Offshore fragments of industry: a pro-market standpoint From a pro-market standpoint, global market forces and the competitive pressures that they generate leave businesses with no choice but to take advantage of lower labour costs elsewhere. In the textile business or the toy business, lower wage costs are the key to profitability; if your competitors find a cheaper labour source, you either follow their example or go out of business. It is not, so the argument runs, because managers lack integrity or compassion that there are now more manufactur 1.2.3 Activity 2 Before you read on, I would like you to dwell for just a moment on the significance of this shift from direct investment by Western firms to the establishment of subcontracting ties with overseas partners. Aside from outside firms being able to p 1.2.2 Offshore fragments of industry The rise of global factories in the 1970s owed much to the rapid improvement in transport and communications technologies which took place at that time and which made it possible to keep in touch with, and control, production processes in different parts of the world. Just as significant was the fragmentation of industrial production whereby parts of the manufacturing process could be relocated over vast distances. Sewing in garment and footwear production, for instance, was among the 1.2.1 Introduction Looking back over the 1970s, it is perhaps hard now to appreciate just how dramatic were the changes to the global map of industry taking place at that time. As more and more of the world's industry shifted from the affluent nations to the poorer, less developed countries in search of a cheaper labour force, the global economic map had to be redrawn to take account of the borders crossed and the distances traversed by firms from wealthier countries seeking to generate higher profits by reloca 1.1.2 Activity 1 You have already glanced at Figure 1 and some of the worki Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material within this unit. Box 4: Four Scenarios for 2050, Royal Commission on Environmental Pollution, 22nd
Report, Energy– The Changing Climate, June 2000. Crown copyright material is reproduced under class licence number C01W0000065 with the p
Box 6: Ozone is blue
Table
