When water is present, what substance combines with iron to form rust?
O2 oxygen !!!! Ferrous oxide, Ferric oxide whatever
When water is present, the substance that combines with iron to form rust is oxygen.
When water is present, the substance that combines with iron to form rust is oxygen. Oxygen is an essential component required for the process of rusting to occur. Here's how you can arrive at this answer by following a logical thought process:
1. Start with the given information: "When water is present, what substance combines with iron to form rust?"
2. Recall the process of rusting: Rusting is an electrochemical process where iron reacts with oxygen in the presence of water to form iron oxide, commonly known as rust.
3. Identify the two main components involved: In the context of rusting, there are three main elements: iron (Fe), oxygen (O), and water (H2O). However, iron is not combining directly with water in this reaction but rather with one of the components.
4. Evaluate the options: We need to determine which substance combines with iron to form rust when water is present. Given the three options (iron, oxygen, and water), we can eliminate iron itself since it is already present and not the one being combined. This leaves us with oxygen and water as the remaining options.
5. Understand the role of water: Although water is required for rusting to occur, it does not directly combine with iron to form rust. Instead, it acts as a facilitator by providing the necessary medium for the reaction to take place.
6. Identify the combining substance: Now we are left with the substance oxygen as the answer. In the rusting process, oxygen combines with iron atoms to form iron oxide (Fe2O3) or hydrated iron oxide (Fe2O3 ยท xH2O), commonly known as rust.
Therefore, the substance that combines with iron to form rust when water is present is oxygen.