Which substance combines with iron in the presence of water to form rust?
oxygen, O2.
Oxygen combines with iron in the presence of water to form rust. The process of rusting involves the oxidation of iron, where oxygen molecules react with iron atoms to form iron oxide, commonly known as rust.
The substance that combines with iron in the presence of water to form rust is oxygen. Rust is a common term for the chemical compound iron(III) oxide, which forms when iron reacts with oxygen and water in a process called oxidation. Here's how you can arrive at this answer on your own:
1. Start by understanding the process of rust formation. Rust is a type of corrosion that occurs when iron or steel undergoes oxidation in the presence of moisture and oxygen.
2. Recall that oxidation is a chemical process in which a substance reacts with oxygen. In the case of rust, iron reacts with oxygen to form iron(III) oxide.
3. Now, you can deduce that the substance combining with iron to form rust is oxygen, as stated in the previous step.
So, in summary, oxygen is the substance that combines with iron in the presence of water to form rust through the process of oxidation.