| define corrosion | the destruction of materials by the chemical reactions with substances in the environment |
| what things can only be described as rusting | iron or alloys of iron like steel |
| other metals apart from iron and alloys of iron are described as | corroding |
| describe the experiment for rusting | -3 test tubes, one containing an iron nail and water, one containing and iron nail in boiled water and with a layer of oil on top and one containing an iron nail in anhydrous calcium chloride power and a rubber bung
-leave for several days, the first test-tube's nail should be covered in rust, the others should have no rust |
| why is the water in test tube 2 boiled | it removes any dissolved oxygen in the water |
| why is anhydrous calcium chloride powder in test tube 3 used | it removed any water from the air in the test-tube |
| explain the results | corrosion requires both air and water to take place |
| how can corrosion be prevented | using grease, paint or electroplating to act as barriers |
| what is commonly used as electroplating a metal and why | aluminium as it reacts with oxygen in the air to form a thin layer of aluminium oxide which prevents the metal from corroding |
| coating a metal in zinc is called | galvanisation |
| what happens if the zinc gets scratched | it still prevents corrosion as zinc is more reactive than iron so zinc corrodes instead of iron |
| what is it called hon a more reactive metal is used to coat a less reactive metal | sacrificial protection |
