Metals Flashcards
Chemical name for rust
hydrated iron (III) oxide
2 stages of Iron rusting
- Iron is oxidised by oxygen, forming Iron (III) oxide
- Iron (III) oxide is hydrated by water
Balanced equation for oxidation of Iron
- 4Fe + 3O2 –> 2Fe2O3
Balanced equation for hydration of Iron (III) oxide
Fe2O3 + H2O –> Fe2O3 x H2O
Rusting prevention methods
- Barriers
- Sacrificial protection
- Galvanisation
What is barrier protection (rust)
- Coating iron in paint, oil, grease or plastic to prevent iron coming into contact w/ oxygen or water
- only works when barrier is intact- if broken, rust happens
What is sacrificial protection (rust)
- Attaching block of more reactive metal (e.g magnesium) to the Iron
- Iron is displaced from rust as soon as it forms
-however Mg has to be replaced often
Equation for sacrificial protection
- Magnesium + iron(III) oxide –> magnesium oxide + iron
what is galvanisation (rust)
- Coating iron in zinc
- works initially as barrier protection, but if it cracks then also sacrificial as zinc more reactive than iron
What is an alloy?
Mixture of metal with one or more other element, usually another metal or carbon
Common alloys:
- Steel ( Iron + carbon)
- Brass (copper + zinc)
- Bronze ( copper + tin)
Positives of alloys
- Harder/ less malleable than normal metals
Why are alloys harder than normal metals?
- made up of different sized atoms/ions
- layers cannot slide over each other as easily
- therefore less malleable
Use of Iron
- To make steel, as it is more useful
Use and contents of low carbon steel
- Iron, 0.1% carbon
- used for making Ships, cars as they are strong but can be hammered to dif shapes
Use and contents of high carbon steel
- Iron, 1% carbon
- used for tools e.g screwdrivers, as they are less malleable than low carbon steel
Use and contents of stainless steel
- Iron, 1% carbon, 10% Chromium
- used for cutlery, cooking utensils as Chromium forms oxide layer preventing corrosion- stay shiny
use of copper + why
- wires, pans, pipes
- as good conductor of heat and electricity
- unreactive and malleable
use of aluminium + why
- aircraft bodies, power cables
- as is low density, but is very strong and conductive
What are metal ‘ores’
- rocks containing metals as compounds with Sulphur and Oxygen
why are metals in ores compounds with Oxygen and Sulphur
- Over long periods of time underground metals have reacted with Oxygen and Sulphur
reactivity series (from least reactive)
- Gold (Au)
- Silver (Ag)
- Copper (Cu)
- [Hydrogen (H)] - not metal
- Lead (Pb)
- Iron (Fe)
- Zinc (Zn)
- [Carbon (C)] - not metal
- Aluminium (Al)
- Magnesium (Mg)
- Calcium (Ca)
- Lithium (Li)
- Sodium ( Na)
- Potassium (K)