Four iron nails are kept for a week. Nail 1 is in tap water open to the air, and nail 2 is in…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Four iron nails are kept for a week. Nail 1 is in tap water open to the air, and nail 2 is in boiled water under a layer of oil. Nail 3 is in dry air over calcium chloride, and nail 4 is in salt water open to the air.
- Which nails rust?
- Which rusts the most?
- What do you learn?
Need a reminder? The key ideaShow
Iron rusts only when both air (oxygen) and water are present; salt speeds it up. Rusting is prevented by painting, oiling, galvanising with zinc, or alloying. Rancidity is the oxidation of fats and oils; antioxidants, airtight packs, cold and nitrogen gas slow it.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Nails 1 and 4: they have both air and water.
Step 2. (b) Nail 4: salt speeds up rusting.
Step 3. (c) Iron needs both oxygen and water to rust, and salt makes it faster.
Answer: as above.
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