3.5.7 Iron, Steel and other metals Flashcards
What is rusting?
The chemical process by which iron is oxidised to form rust.
What is the chemical name for rust?
Hydrated iron(III) oxide.
What is the balanced equation for rusting?
Fe(s) –> Fe2O3(s) –> Fe2O3.xH2O(s)
What are the physical changes from iron to rust?
Grey Brown
Shiny —> Dull
Malleable Brittle
What are the two stages of rusting?
Iron is oxidised by oxygen to from iron(III) oxide.
Iron(III) oxide is hydrated by water to form hydrated iron(III) oxide.
What is a method to prevent rusting? (b)
Using barriers: coating the iron in paint, oil, grease or plastic prevents the iron coming in contact with oxygen or water.
What is a method to prevent rusting? (s)
Sacrificial protection: attach a block of a more reactive metal (magnesium) to the iron. this works by displacing the iron from the rust as soon as it forms.
What is a method to prevent rusting? (g)
Galvanising: coating the iron in zinc. Prevents iron contacting oxygen or water and if there is a crack, zinc is more reactive and so acts as sacrificial protection as well.
What is an alloy?
Alloys are a mixture of a metal with one or more other elements.
What are three commonly known alloys?
Steel - Iron + Carbon
Brass - Copper + Zinc
Bronze - Copper + Tin
Why are alloys harder and less malleable than pure metals?
Alloys have different sized ions which prevent the layers of metal ions from sliding over each other.
What is a use of iron?
Making steel because steel is more useful than iron.
What is a use of low-carbon steel?
Ships, cars, bridges etc. because it is strong but it can still be hammered into different shapes because it is low carbon.
What is a use of high-carbon steel?
Tools because it is less malleable.
What is a use of stainless steel?
Cutlery, cooking utensils, kitchen sinks because Cr forms oxide layer that resists corrosion, so it stays shiny and clean.
