Give three definitions for oxidation.

Imagine you have a wallet full of cash, and suddenly you start giving away your money. In chemistry, we can compare this to atoms or molecules that 'give away' electrons, which is known as oxidation. During electron transfer in oxidation, an atom, molecule, or ion loses electrons, resulting in an increased oxidation number.

Let's look at a simple example: when sodium (Na) reacts with chlorine (Cl) to form sodium chloride (NaCl), the sodium atom donates an electron to chlorine, becoming a positively charged sodium ion (Na+). Meanwhile, chlorine gains an electron, becoming a negatively charged chloride ion (Cl-). In this transaction, sodium is oxidized, and its oxidation state increases from 0 to +1.

Understanding electron transfer is crucial because it helps to explain redox reactions, which are the foundation of many processes both in natural systems, like respiration, and industrial applications, like battery operations.

The term 'oxidation' might make you think about rust, and you wouldn't be wrong. Rust is a result of oxidation, where oxygen from the air reacts with iron to form iron oxide. This concept comes from the historical definition where oxidation literally meant adding oxygen to a substance. Many chemical reactions, such as the combustion of fuels, involve the addition of oxygen.

When a molecule gains oxygen, this often changes its chemical properties. Take, for instance, the burning of methane (CH₄) in the presence of oxygen (O₂), resulting in carbon dioxide (CO₂) and water (H₂O). Here, the carbon in methane gets oxidized as it bonds to oxygen. This conversion is a basis for producing energy in power plants and car engines.

In contrast with gaining oxygen, oxidation can also mean losing hydrogen. This might sound less intuitive, but remember that hydrogen atoms usually come with electrons. When they leave the molecule, they take their electrons along for the ride.

For example, when ethanol (C₂H₅OH) is converted into acetaldehyde (CH₃CHO), it loses two hydrogen atoms. This removal is considered oxidation. A practical application of understanding this form of oxidation includes biochemistry, where enzymes in our bodies oxidize alcohol, transforming it into compounds that can be further broken down and eliminated. Knowing how hydrogen removal constitutes oxidation is important for students studying organic chemistry or involved in biochemical research.