Template:HideTOC The rusting of an old car. A burning campfire. A toy battery-operated car. The chemical processes in your body that break down carbohydrates to produce water, carbon dioxide and energy. The ripening of fruit. It's not easy to see what all of these types of reactions have in common, but they all belong to a very important category of chemical reactions known as oxidation-reduction (or redox) reactions. 16.1: The End of the Internal Combustion Engine? 16.2: Oxidation and Reduction: Some Definitions "Redox" is short for "oxidation and reduction", two complimentary types of chemical reactions. The term oxidation originally referred to substances combining with oxygen, as happens when an iron bar rusts or a campfire log burns. We often refer to these two examples as corrosion and combustion. Reduction originally referred to the process of converting metal ores to pure metals, a process that is accompanied by a reduction in the mass of the ore. 16.3: Oxidation States - Electron Bookkeeping Redox reactions are all about electrons being transferred from one substance to another, so it would be useful if we had a system for keeping track of what gains and what loses electrons, and how many electrons are involved. We do - our record-keeping system is called Oxidation Numbers. You may remember from earlier chemistry classes something called electronegativity. 16.4: Balancing Redox Equations Another way to balance redox reactions is by the half-reaction method. This technique involves breaking an equation into its two separate components - the oxidation reaction and the reduction reaction. Since neither oxidation nor reduction can actually occur without the other, we refer to the separate equations as half-reactions. 16.5: The Activity Series: Predicting Spontaneous Redox Reactions Single-replacement reactions only occur when the element that is doing the replacing is more reactive than the element that is being replaced. Therefore, it is useful to have a list of elements in order of their relative reactivities. The activity series is a list of elements in decreasing order of their reactivity. Since metals replace other metals, while nonmetals replace other nonmetals, they each have a separate activity series. 16.6: Batteries: Using Chemistry to Generate Electricity Electrochemical cells used for power generation are called batteries. Although batteries come in many different shapes and sizes there are a few basic types. You won't be required to remember details of the batteries, but some general information and features of each type is presented here. Batteries are one way of producing this type of energy. Many important chemical reactions involve the exchange of one or more electrons, and, therefore we can use this movement of electrons as electricity. 16.7: Electrolysis: Using Electricity to Do Chemistry Galvanic cell produce electricity from chemical reactions. Some reactions will, instead, use electricity to get a reaction to occur. In these reactions, electrical energy is given to the reactants causing them to react to form the products. These reactions have many uses. For example, electrolysis is a process that involves forcing electricity through a liquid or solution to cause a reaction to occur. Electrolysis reactions will not run unless energy is added to the system. 16.8: Corrosion: Undesirable Redox Reactions Corrosion of metals is a serious economic problem. Corrosion occurs as a result of the spontaneous electrochemical reaction, as the metal undergoes oxidation.