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)
Why are Gold and Silver native ( not in ores)
- not reactive enough to combine with oxygen or sulphur
- therefore found chemically uncombined
Methods of metal ore extraction
- Using electricity
- Carbon extraction
How does carbon extraction work
- metals less reactive than carbon can be displaced from their ore when heated with carbon
What is a displacement reaction
- When more reactive metals displace less reactive metals from their compounds
example of displacement reaction
- magnesium displaces copper from copper sulphate
equation for magnesium/copper sulphate displacement reaction
Magnesium + Copper sulphate –> Magnesium sulphate + copper
Main observations to think about for displacement reaction
- Solid colour change
- solution colour change
Two components of metal structure
- lattice of positive metal ions
- sea of delocalised electrons
What is metallic bonding
The electrostatic attraction between the positive metal ions and negative delocalised electrons
Metallic bonding is…
a very strong attraction
properties of metals
-High melting points
-conduct electricity
-Malleable
Why metals have high melting point
- metallic bonding very strong, lots of energy needed to break bonds
why metals conduct electricity
- delocalised electrons free to move through lattice, carrying charge
why metals malleable
layers of metal ions can slide over each other
metal and water reaction equation
metal + water –> metal hydroxide + hydrogen
example of metal and water reaction
magnesium + water –> magnesium hydroxide + hydrogen
observations made in metal and water reaction
- effervescence due to hydrogen gas produced
- solid disappearing due to being used up in reaction
group 1 (alkali) metals reaction with water
- violent reaction
- as they are highly reactive
example of group 1 metal and water reaction
lithium + water –> lithium hydroxide + hydrogen
Reactions of Li, Na and K in water similar observations
- solid floats- less dense than water
- effervescence- production of H gas
- solid moves- effervescence propels it around surface
- solid disappears- used up in reaction
colour of universal indicator in solution of metal and water after reaction?
- dark blue
- metal hydroxide created- alkali
reactivity of group 1 metals down the group
- more reactive
why are group 1 metals reactive
- only need to lose 1 outer shell electron to get full outer shell
why is it easier for group 1 metal atoms to react further down group?
- 1 outer shell electron must be lost to react
- down group=further away from nucleus
- further away from nucleus- weaker attraction between electron and nucleus
- less energy needed to break attraction
metal and steam reaction equation
metal + steam –> metal oxide + hydrogen
example of metal and steam reaction
magnesium + steam –> magnesium oxide + hydrogen
why do metals react with cold water and hot steam differently?
- steam has more energy
- therefore both hydrogen bonds in water can break
- therefore metal ‘oxide’ not ‘hydroxide’
how do conduct metal and steam reaction ( Mg)
- horizontal tube
- wet wool and magnesium placed inside
- tube heated
- Hydrogen gas (product) escapes tube and is ignited to safely destroy it
Acid and metal reaction
metal + acid –> salt + hydrogen
example of acid and metal reaction
magnesium + sulphuric acid –> magnesium sulphate + hydrogen
observations of metal and acid reaction
- metal disappears as it is used in reaction
- effervescence as hydrogen gas is produced
why do group 1 all have the same chemical properties
they all have one electron in their outer shell
characteristics of group 1 metals
- need to be stored in oil
- soft so can be cut easily
- oxidise quickly so become dull when cut
- low mtp/density
