Grade 6 → chemical reactions ↓
Oxidation and Reduction
In chemistry, oxidation and reduction are two important concepts that occur during chemical reactions. These concepts may seem a bit complicated at first, but when we break them down into simpler terms, they become much easier to understand. This lesson will help you understand these concepts and their relation to chemistry.
What is a chemical reaction?
Before diving into oxidation and reduction, it is important to understand what a chemical reaction is. A chemical reaction is a process in which substances, known as reactants, undergo changes to form new substances, known as products. During this process, atoms are rearranged, and old bonds are broken to form new bonds.
Basic concepts of oxidation and reduction
Oxidation and reduction involve the transfer of electrons between atoms or molecules. Let's define them:
Oxidation is the process of losing electrons. When a substance loses electrons, it becomes oxidized.
Reduction is the process of gaining electrons. When a substance gains electrons, it is reduced.
To remember these concepts, you can use the mnemonic "LEO-GER": loss of electrons is oxidation, and gain of electrons is reduction.
Oxidation and reduction with examples
Example 1: Rusting of iron
If you leave an iron nail outside, it may eventually rust. Rusting is a type of oxidation reaction. Let's take a look at the process:
4Fe + 3O 2 → 2Fe 2 O 3
In this reaction, iron (Fe) combines with oxygen (O 2) to form iron oxide (Fe 2 O 3). The iron is oxidized, which means it loses electrons, forming Fe 2+ ions, and the oxygen is reduced, which means it gains those electrons.
Example 2: Combustion of hydrogen
Another common example of oxidation and reduction is the combustion of hydrogen gas.
2H 2 + O 2 → 2H 2 O
In this reaction, hydrogen (H 2) reacts with oxygen (O 2) to form water (H 2 O). Here, hydrogen is oxidized because it loses electrons, and oxygen is reduced because it gains electrons to form water.
Understanding oxidation numbers
In chemical reactions, understanding oxidation numbers can help identify which atoms have been oxidized and which have been reduced. Oxidation numbers are a way to keep track of electrons in atoms and molecules.
- Each atom in a molecule has an oxidation number.
- In simple ions, it is equal to the charge of the ion. For example, the oxidation number of Na+ is +1.
- For molecules, the oxidation number must be equal to the overall charge of the molecule.
Example: Oxidation number in water
The oxidation number in water (H2O) can be determined as follows:
- The oxidation number of hydrogen is +1.
- The oxidation number of oxygen is -2.
- The sum of oxidation numbers (2(+1) + (-2) = 0).
Using oxidation numbers, we can determine which element is oxidized and which is reduced in a reaction. For example, in the combustion of hydrogen, the oxidation number of hydrogen changes from 0 to +1, and the oxidation number of oxygen changes from 0 to -2.
Redox reactions
Oxidation and reduction always happen together which is what we call a redox reaction. In every redox reaction, there are two main parts:
- The oxidation part, where a chemical species loses electrons.
- The reduction part, where the other species gains those electrons.
Consider a simple reaction between zinc metal and copper ions:
Zn + Cu 2+ → Zn 2+ + Cu
In this response:
- Zinc (Zn) loses electrons and is oxidized to Zn2+.
- Copper ions (Cu2+) are reduced to copper metal (Cu) and gain electrons.
A simple redox reaction visualization
Visualizing the movement of electrons in a redox reaction can enhance understanding. Consider the zinc and copper reaction as shown below:
Here the electron flow is clear from zinc to copper, in which zinc is getting oxidized and copper is getting reduced.
Applications of redox reactions
Redox reactions are all around us and have many applications, including:
Batteries
Batteries work on the principle of redox reactions. For example, in a typical alkaline battery, zinc and manganese dioxide undergo a redox reaction to produce electricity.
Metabolism
Our body uses redox reactions in metabolism to release energy from the food we eat. In this process glucose is oxidized and oxygen is reduced, producing energy for our cells.
Photosynthesis
Plants carry out photosynthesis using redox reactions. During photosynthesis, carbon dioxide is reduced to form glucose, and water is oxidized to release oxygen.
Conclusion
Oxidation and reduction are fundamental concepts in chemistry that explain many phenomena around us. Understanding these concepts helps us understand how different chemical reactions occur and their significance in the natural world and technology. Remember, oxidation involves the loss of electrons, and reduction involves the gain of electrons, which always occur together in redox reactions. From rusting nails to running batteries, these reactions are vital to life and technology as we know it.