All about Oxidation & Reduction
All about Oxidation & Reduction
  • 승인 2014.05.13 10:11
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The purpose of this section is to explain the phenomena that we can see and feel around us scientifically. At this point, it is impossible not to mention oxidation and reduction. Chemistry is the most closely related with modern life among the fields of science. Oxidation and reduction is one of the most important theories in chemistry in terms of what is close to our life. Then, let’s find out what the ‘Oxidation – Reduction Reaction’ is.

● Definition of Oxidation and Reduction

Historically, corrosion of steel structures such as buildings and bridges has been an important problem. Our ancestors already knew that the cause of this problem was a combination of metal and oxygen. They focused on oxygen and called this phenomenon ‘oxidation’. Then, ancestors defined ‘reduction’ as a reversed process of oxidation, or oxidized metal’s detachment into metal and oxygen.

- Oxidation Number
Oxidation number is the number of charge (charge is amount of electricity) that each atom in one compound has. The more electrons that exist, the less the oxidation number because electrons have a negative (or minus) temper. In other words, if oxidation number declines, then it means an atom gets some electrons. As reduction occurs, the oxidation number decreases. Thus, we call the reversed process of oxidation ‘reduction’ as it has the same meaning as decrease.

 Oxidation and Reduction in Our Lives
- Cleaning Our Clothes
We use bleach to get rid of stains on clothes or mold. However, you may have not recognized that the principle of bleach is an oxidation and reduction reaction. There are two kinds of bleach, oxidation bleach and reduction bleach. We are going to learn about only oxidation bleach because it is more common in our life.
When we use oxidation bleach, it produces oxygen. We call this oxygen active oxygen. Then, it is willing to take electrons from colored materials on the clothes like stain. Through this process, colored materials are decomposed from clothes and clothes recover their original color.

- Perming Our Hair
We can also find this phenomenon in a hair salon. When we get a perm, we use permanent waving agents. By using a reducing agent, it reduces (opposite meaning of oxidize) our hair and changes its atomic form. After curling our hair, we apply the oxidizing agent. It makes our hair oxidized and fixes changed form of the hair. We use thioglycolic acid as a reducing agent and hydrogen peroxide as an oxidizing agent.

- Iron’s rust

This chemical formula is a typical case of oxidation. This formula means that four solid state iron atoms and three gas state oxygen atoms react and make two solid state oxidized iron atoms. This formula explains the process of iron’s corrosion. Since iron combines with oxygen, we can call this phenomenon oxidation.

- Oxidation and Reduction in CSI
In the 18th episode of CSI(Crime Science Investigation) season 6, one criminal committed a crime using the oxidation-reduction reaction. The criminal attached sodium to a shower spigot. When the victim turned on the shower, an explosion occurred. Someone might suspect this phenomenon as to why sodium explodes when it meets water. Maybe that person misunderstands the difference between salt and sodium. Koreans are familiar with natrium(same term of sodium) as salt since they are sensitive to the content of natrium in salt. However, sodium is not equal to salt, just a component of salt.
Sodium is one kind of alkali metals which have huge reactivity and are most willing to lose an electron and oxidize among the elements. When it meets water, its process of oxidation is very fast and it reacts intensely. In this situation, its condition is too unstable and a large amount of heat is released. Consequently, an explosion occurs.

 Preventing Oxidation with the Principle of Oxidation and Reduction
As mentioned before, oxidation was big problem for our ancestors. To prevent oxidation, humans use the principle of oxidation and reduction. There are three methods to prevent metal’s oxidation.
Most people can easily think that painting is just for art. However, there is an important purpose for painting which is preventing metal from oxidation. This method is a kind of ‘Oxide Film Treatment’. It is blocking the metal from air so as not to contact with causes of oxidation like oxygen. By painting metal, a protective film occurs over paint that protects metal from oxygen.
The second method is making alloys. An alloy is mixed metals. If more than two metals are mixed, their tempers are changed. Their oxidation reactivity is no exception. If we mix two metals, their temper to easily oxidize disappears.
The last method is cathodic protection. This method is applied from metal’s reactivity. If someone wants to keep metal from oxidizing, they attach more reactive metal to another metal. Then the attached metal will be oxidized instead. For instance, vessels consist of iron. Since they always contact water, they can easily rust. By attaching more reactive metals like magnesium (Mg) and zinc (Zn), those are rusted instead of iron and we can prevent iron’s oxidation in water. Also, we can find this method in iron oil tanks, to which people attach magnesium and zinc because of the same mechanism of the former example.

- K>Ca>Na>Mg>Al>Zn>Fe>Ni>Sn>Pb>H>Cu>Hg>Ag>Pt>Au
This shows ‘Metal Reactivity’. The closer the metal element is to Potassium (K), the more willing it is to react with oxygen. For example, potassium is more willing to combine with oxygen than sodium (Na). Also, Aurum (chemical term for gold, Au) is unwilling to react with oxygen.

The more human technologies are developed, the higher the expectation and the more things produced in our life. Now, look around and think carefully about whether there are things which apply the ‘Oxidation – Reduction Reaction’. Can you find it? Then you may understand this reaction very well.

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