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6. An unwanted reaction between metals and the atmosphere and water.
7. Chemical like sodium hydroxide with a pH value greater than 7.
10. Iron corrodes in the presence of air and water to form ...
12. Most common magnetic element. Corrodes to form rust.
14. Industrially important form of iron used for car bodies and structural girders.
15. Soft, reactive, low density metallic element used in yellow street lights.
16. Mild corrosion of silver, for example.
17. The most common solvent - contains the elements hydrogen and oxygen.
18. The lowest density metallic element. It is soft and reactive.
19. Non metallic gaseous element needed for respiration.

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1. Unreactive metallic element with extremely high electrical conductivity used for coins.
2. Chemical with a pH value less than 7. Sulphuric or hydrochloric are examples.
3. Orange metallic element used for household electrical wiring.
4. Very unreactive, expensive yellow metallic element used for jewellery.
5. Where iron is produced in industrial quantities (5,7).
8. Soft, reactive, low density metallic element, important for healthy plant growth.
9. Silver-white low density metallic element used for saucepans and bicycle wheel rims.
11. Soft, dense, unreactive grey metallic element used in car batteries.
13. When a complete reaction takes place between acid and alkali they are said to ...