1. Rusting – Lesson Objectives Understand how salt water affects rusting. Understand that rusting is an oxidation reaction (iron reacts with oxygen forming an oxide). Construct the word equation for rusting Explain why aluminium does not corrode in moist conditions.

2. What has caused this iron to turn red? Can you guess why it happened?

3. When iron rusts… Rusting

4. … it reacts with oxygen and turns back to the iron oxide it was made from.

5. But things are not that simple.

6. Iron does not rust in the desert, even though there is plenty of oxygen in the air.

7. Rusting also needs water. Iron + Oxygen + Water  Hydrated Iron (iii) Oxide

8. Redox Reactions Redox is a short way of saying: Reduction and oxidation Oxidation meant adding oxygen to a substance. Rusting (iron becoming iron oxide) is an example of oxidation. Reduction meant taking oxygen away. Extracting iron from iron oxide in the blast furnace is reduction. Early on in chemistry these words had very straightforward meanings.

9. Redox reactions: oxidation and ions Whenever metals react with oxygen they form ionic compounds and the metal loses electrons to form positively charged ions. Eg. When magnesium burns to form magnesium oxide magnesium atoms (no charge) become magnesium ions (2+ charge) by losing 2 electrons to oxygen atoms. Mg O 2 e - to give Mg 2+ O 2- Oxidation involves loss of electrons.

10. Redox Reactions: oil rig Oil Rig An easy way of remembering this is “Oil Rig”! O oxidation Iis L loss R reduction Iis G gain of electrons

11. Prevention Cover in oil Paint Galvanise – coat with Zinc Stainless steel – mixture of Fe and C and Chromium (Cr)

12. Here’s a puzzle ironmystery metal identical nut and bolt in identical conditions! identical except that one is made of iron and the other is made from a mystery metal

13. the mystery metal is aluminium aluminium does not corrode in moist conditions so it is suitable for window frames

14. …. and other things that get wet

15. How does it happen? aluminium reacts quickly with the oxygen in the air a layer of aluminium oxide forms no more oxygen can reach the metal

16. What is rust? – Write and answer in your book. E/F – Rust requires both air AND water. It is and Orange/brown substance. C/D - Rust is ‘Iron Oxide’ B/C - Iron + Oxygen + Water  Hydrated Iron (iii) Oxide