You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?
The iron nail dipped in oil will not rust.
Rusting requires both air (oxygen) and water to occur. The oil forms a protective coating over the iron nail, preventing both air and water from coming into contact with the iron surface.
The nail in water will rust because water alone can still allow some air to dissolve in it. The nail in vinegar will rust even faster because vinegar is acidic and accelerates the corrosion process.
Oil acts as a barrier, similar to how painting, oiling, and greasing are mentioned as methods to prevent rusting.
Explanation
The chapter explains through Activity 4.5 that rusting of iron requires both air and water. Brown deposits (rust) develop only when iron is exposed to moist air. The chapter also mentions that rusting can be prevented by painting, oiling, and greasing—these methods create a protective barrier that prevents contact with air and moisture. Oil coating on the iron nail serves the same protective function.
Solution Steps
The iron nail dipped in oil will not rust.
Rusting requires both air (oxygen) and water to occur.
Oil forms a protective coating that prevents air and water from contacting the iron surface.
The nail in water will rust because water allows some air to dissolve in it.
The nail in vinegar will rust faster because vinegar is acidic and accelerates corrosion.
Oil acts as a barrier, similar to painting, oiling, and greasing methods.