Oxygen and Oxidation
OXIDATION AND REDUCTION
Oxygen makes up only about 20% of the air, yet is the essential component for so many reactions. Without it fuels would not burn, iron would not rust and we would be unable to obtain energy from our food molecules through respiration. Indeed animal life on the planet did not evolve until a certain concentration of oxygen had built up in the atmosphere over 600 million years ago. The term oxidation has been in use for a long time to describe these and other reactions where oxygen is added. Oxidation, though, is only half of the story, as it is always accompanied by the opposite process reduction, which was originally thought of in terms of loss of oxygen. Later, however the terms widened to include a much broader range of reactions. We now define these two processes, oxidation and reduction, as occurring whenever electrons are transferred from one reactant to another – and many of these reactions does not involve oxygen at all. For example photosynthesis, the process in which plants store chemical energy from light energy, involve oxidation and reduction reactions although oxygen itself is not used. Transferring electrons from one substance to another leads to a flow of electrons, in other words to an electric current. Thus chemical reactions can be used to generate electricity – a simple battery works by using a reaction of oxidation and reduction in this way. As we will see, we can also reverse the process and use an electric current to drive a reaction to oxidation and reduction – this is the process known as electrolysis which has developed to become one of the most important industrial processes on which we depend. An understanding of oxidation and reduction is therefore at the heart of understanding a large branch of chemistry both in the laboratory and beyond.
Chemistry
OXYGEN
Oxidation is the loss of electrons, reduction the gain of electrons.
The Nobel Prize in Chemistry 1992
The Royal Swedish Academy of Sciences awards
Oxygen makes up only about 20% of the air, yet is the essential component for so many reactions. Without it fuels would not burn, iron would not rust and we would be unable to obtain energy from our food molecules through respiration. Indeed animal life on the planet did not evolve until a certain concentration of oxygen had built up in the atmosphere over 600 million years ago. The term oxidation has been in use for a long time to describe these and other reactions where oxygen is added. Oxidation, though, is only half of the story, as it is always accompanied by the opposite process reduction, which was originally thought of in terms of loss of oxygen. Later, however the terms widened to include a much broader range of reactions. We now define these two processes, oxidation and reduction, as occurring whenever electrons are transferred from one reactant to another – and many of these reactions does not involve oxygen at all. For example photosynthesis, the process in which plants store chemical energy from light energy, involve oxidation and reduction reactions although oxygen itself is not used. Transferring electrons from one substance to another leads to a flow of electrons, in other words to an electric current. Thus chemical reactions can be used to generate electricity – a simple battery works by using a reaction of oxidation and reduction in this way. As we will see, we can also reverse the process and use an electric current to drive a reaction to oxidation and reduction – this is the process known as electrolysis which has developed to become one of the most important industrial processes on which we depend. An understanding of oxidation and reduction is therefore at the heart of understanding a large branch of chemistry both in the laboratory and beyond.
Chemistry
OXYGEN
Oxidation is the loss of electrons, reduction the gain of electrons.
The Nobel Prize in Chemistry 1992
The Royal Swedish Academy of Sciences awards