A great example of a temporary chemical reaction is the process of rusting. Rusting is a slow reaction between iron, oxygen, and moisture in the environment that forms iron oxide, commonly known as rust. However, if you remove the moisture or the oxygen, the rust can be reversed back to iron through a reduction reaction.
In simpler terms, when you leave an iron object outside, it can react with water and air, creating rust. This is a temporary state because, technically, iron and rust are different chemical forms. If you were to expose rust to certain conditions, such as carbon monoxide, you could remove the oxygen, effectively reversing the reaction and returning almost all the iron back. Thus, while rusting results in the change of iron to rust, under specific circumstances, you can revert that process, representing the temporary nature of this chemical reaction.