Page 905 - Chemistry--atom first

Chapter 17 | Kinetics 895
Chapter 17 Kinetics
Figure 17.1 An agama lizard basks in the sun. As its body warms, the chemical reactions of its metabolism speed up.
Chapter Outline
17.1 Chemical Reaction Rates
17.2 Factors Affecting Reaction Rates 17.3 Rate Laws
17.4 Integrated Rate Laws
17.5 Collision Theory
17.6 Reaction Mechanisms
17.7 Catalysis
Introduction
The lizard in the photograph is not simply enjoying the sunshine or working on its tan. The heat from the sun’s rays is critical to the lizard’s survival. A warm lizard can move faster than a cold one because the chemical reactions that allow its muscles to move occur more rapidly at higher temperatures. In the absence of warmth, the lizard is an easy meal for predators.
We have now developed a relatively complete picture of chemical and physical processes, encompassing the contributions of energy (enthalpy changes) and entropy (order and disorder). Each ultimately contributes to the determination of reaction spontaneity – that is, whether or not a process will take place spontaneously. We have also looked at the important concept of zero free energy change, where a system comes to equilibrium. What we have not yet examined is whether a process reaches equilibrium quickly or slowly.
Consider, for example, the advertising slogan “Diamonds are forever.” Are they? A look at the table of enthalpy and entropy values tells us the thermodynamically stable form of carbon is actually graphite, not diamond. Further, a calculation shows us that the conversion of diamond into graphite is indeed a spontaneous process – the G value is negative. So why do we not see diamond spontaneously forming graphite? The answer is found in the topic of this