C10 Flashcards
What are the physical properties of metals?
Conduct heat and electricity
Malleable (hammered into different shapes)
Ductile (wire)
Lustrous (shiny)
High density
High melting/boiling points
Form positive ions (electron loss)
Form basic oxides
Strong
Solid at room temp (-mercury)
Explain metallic bonding
Metal -> regular lattice -> tightly pack layers
Outer electrons separated from atoms creating a ‘sea of electrons’
> electrons delocalized -> free to move thought the whole structure
> positive ions
Metal ions are attracted to the sea of electrons -> metallic bonding
How does the structure of metals explain:
High melting and boiling points
Strong attractive forces between ions -> strong metallic bonds
Lots of heat required to break the bonds
How does the structure of metals explain:
Conducting heat and electricity
Delocalized electrons -> conduct heat and electricity
Metals heated -> electrons gain kinetic energy -> moves faster -> electrons transfer gained energy through the metal
Electrons carry charge -> electrons enter on end of the metal -> causes delocalized electrons to displace itself -> electrons flow -> electricity is conducted
How does the structure of metals explain:
Metals strength, malleability, ductility
Metals hit -> layers of metal ions can slide over each other -> no shatter
> layers of ions can take different positions
Bonding is not disrupted:
Outer electrons so not ‘belong’ to any one ion so delocalized electrons can move
This property makes metals malleable and ductile
How does the structure of metals explain:
Corrosive
Corrosion -> gradual destruction of a metal due to reactions with other chemicals in its environment
>makes metals weaker
Coating the surface with paint/certain chemicals -> protection
Metals corrode at different rates
> gold -> uncreative -> does not corrode
Define alloy
An alloy is a MIXTURE of 2+ metals or a metal with a non-metal such as carbon
Why are alloys used? How does this relate to properties of alloys as opposed to pure metals?
Alloys often have different properties to their metals they contain:
> strength
> hardness
> resistance to corrosion
> resistance to extreme temperatures
Alloys contain atoms of different sizes -> distorts regular arrangement of atoms
> makes it more difficult for layers to slide -> alloys are harder than pure metals
What are some common alloys and their uses?
Brass = copper + zinc
> stronger
> used in musical instruments, door knobs, ornaments
Stainless steel = iron + other elements (chromium, nickel, carbon)
> cutlery
> because of its hardness, resistance to corrosion
Iron + tungsten
> hard and resistant to high temps
Iron + chromium or nickel
> resistant to corrosion
Aluminium + copper, manganese, silicon
> aircraft body production
> stronger but low density
What are the different types of steel (properties or iron changed by the controlled use of additives)
Name:
Amount/element alloyed with:
Use:
Property:
Pure iron -> not very useful because it is too soft and rust easily
Too much carbon -> brittle
Too little carbon -> no strong enough
Mild steel:
> 0.25% carbon
> used in: car body panels, wires
> soft + malleable
High carbon steel:
>0.5 - 1.4% carbon
> tool and chisel
> hard
Low alloy steel:
> 1 - 5% of another metal (CR, NI, TI)
> construction, bridges, high speed tools
> hard, strong, low ductility + malleability
Stainless steel:
> 20% chromium + 10% nickel
> cutlery, sinks, chemical plants
> strong, resistant to corrosion
List metals in order of reactivity (+ carbon and hydrogen)
(Hint: please send (lions) cats, monkeys, and cute zebras into hot countries signed Gordon)
Potassium
Sodium
lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Hydrogen
Copper
Sliver
Gold
State the reaction by the metal in:
Cold water
Potassium
> react violently
Sodium
> reacts quickly
Calcium
> reacts less strongly
————
> metal below calcium -> react with steam not cold water
> metal below calcium + steam -> metal oxide + hydrogen
Magnesium
> slow reaction (with steam)
Aluminium
> slow reaction (with steam)
Carbon
> —
Zinc
> very slow reaction (with steam)
Iron
> very slow reaction (with steam)
Hydrogen
> more reactive than hydrogen:
-> metal + water -> metal hydroxide + hydrogen gas
Copper
> no reaction
Sliver
> no reaction
Gold
> no reaction
State the reaction by the metal in:
Acid
Potassium
> reacts violently
Sodium
> reacts violently
Calcium
> reacts vigorously
Magnesium
> reacts vigorously
Aluminium
> reacts readily
Carbon
> —
Zinc
> reacts less strongly
Iron
> reacts less strongly
Hydrogen
> metals above hydrogen will react to dilute metals
> metal + acid -> salt + hydrogen
Copper
> no reaction
Sliver
> no reaction
Gold
> no reaction
State the reaction by the metal in:
Oxygen
Potassium
> reacts quickly
Sodium
> reacts quickly
Calcium
> reacts readily
Magnesium
> reacts readily
Aluminium
> reacts readily
Carbon
> under carbon in reactivity series -> carbon will displace them in their oxides forming carbon dioxide
-> reduction
Zinc
> reacts
Iron
> reacts
Hydrogen
> —
Copper
> reacts
Sliver
> reacts
—————-
> metal + oxygen -> metal oxide
Gold
> no reaction
How does loss of electrons relate to the reactivity of a metals?
Metal atoms → positive ions by loss of electrons when they react with other substances
The tendency of a metal to lose electrons is a measure of how reactive the metal is
A metal that is high up on the series loses electrons easily and is thus more reactive than one which is lower down on the series
Explain the displacement reaction between metals and aqueous solutions of metal salts
> metal (1) will displace metal (2) that is LOWER on the reactivity series
-> metal (2) (less reactive) must be a solution of its salt
> this is because metal (1) is more reactive (loss electrons and creates ions more readily) -> better reducing agents
> less reactive metal (2) is better electron acceptor -> is reduced (gains electrons)
This can be used to to deduce the order of reactivity (if you don’t know them)
Metals can also displace oxides:
Ex: Iron (II) oxide + aluminium -> iron + aluminium oxide
Give an example of a displacement reaction between metals and aqueous solutions of metal salts
Magnesium and copper sulphate
Magnesium + copper sulphate
> magnesium -> reactive
-> can displace copper from copper sulphate solution
> magnesium loses its electrons easily and ions of copper will gain these electrons -> forms elemental copper
Magnesium + copper sulphate -> magnesium sulphate + copper
Mg + CuSO4 -> Mg SO4 + Cu
How can you deduce the order of reactivity from a given seat of experimental result?
Observed through reactions between metals, water, acids, oxygen
> more vigorous reaction -> higher up on reactivity scale
-> will have to use a combination of reactions (ex: with water)
> less reactive metals react slowly or not at all
-> will have to use a combination of reactions (ex: dilute acid)
> temperature change in a reaction can also be used
-> greater temperature change -> more reactive
How does a metals reactivity determine its method of extraction?
Most metals found in earths crust are combined with other elements in ORES (usually an oxide)
> iron is found combined with oxygen -> haematite and magnetite
The reactivity of a metal determines method of extraction
> above carbon -> electrolysis
-> ex: aluminium from bauxite
> below carbon -> extracted by reduction
-> iron from haematite
> platinum, gold, silver, copper -> occur native
What metals use electrolysis/reduction/found as pure for extraction?
Electrolysis:
> Large amounts of electricity needed -> expensive
> electrolysis of molten chloride or oxide
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Reduction:
> extracted by heating its reducing agent
> cheap
Zinc
Iron
Found as pure:
Copper
Silver
Gold
What is the reaction in the extraction of iron from haematite (chemical equation)?
C + O2 -> CO2
> burning of carbon to provide heat + make CO2:
C + CO2 -> 2CO
> reduction of CO2 to CO
Fe2O3 + 3CO -> 2Fe + 3CO2
> reduction of iron (III) oxide by CO
CaCO3 -> CaO + CO2
> thermal decomposition of limestone to produce CaO
CaO + SiO2 -> CaSiO2
> formation of slag
Explain the process of extraction of iron using a blast furnace
Raw materials: iron ore, coke (impure carbon), limestone added to top of the furnace
> hot air blown into the bottom
ZONE 1 (BOTTOM): oxidation
> coke burns in hot air -> carbon dioxide
> reaction exothermic -> heats the furnace
> Carbon + oxygen -> carbon dioxide
ZONE 2 (MIDDLE): redox
> at high temp -> coke reacts with CO2 to form CO
> CO2 reduced to CO
> carbon + carbon dioxide -> carbon monoxide
ZONE 3 (TOP): redox
> carbon monoxide reduces iron (III) oxide
-> iron ore -> iron
> iron will melt and collect at bottom of furnace (taped off)
> iron (III) oxide + carbon monoxide -> iron + carbon dioxide
> some iron (III) oxide reacts with carbon to form carbon dioxide
Iron (III) oxide + carbon -> iron + carbon dioxide
SLAG:
> limestone added to the furnace to remove impurities
-> limestone thermally decomposes to form calcium oxide
> Calcium oxide reacts with silicon dioxide (impurity) -> calcium silicate
-> this is slag -> collects at bottom on top of iron (tapped off)
> CaO + SiO2 -> CaSiO3
What are the uses of aluminum?
Airplane bodies
> high strength to weight ratio
> low density
Overhead power cables
> good conductor of electricity
> low density
Saucepans
> good conductor of heat
Food can
> non-toxic
> resistant to corrosion and acidic food stuffs
Window frames
> resistant to corrosion
Describe and explain the apparent unreactivity of aluminum
Aluminum -> high in reactivity series
> but in reality its doesn’t react with water and with acid is slow
That is because it reacts readily with oxygen -> forms protective layer of aluminum oxide (THIN)
> layer prevents reaction with water and dilute acids
> aluminum can behave as if unreactive
What is rust?
A chemical reaction between iron, water and oxygen to form hydrated iron (III) oxide AKA rust
Rust can be prevented with barriers such as:
> grease
> paint
> oil
> plastic
ONLY IRON AND STEEL CAN RUST
Explain sacrificial protection (+ an example)
More reactive metals attached to less reactive metals
> more reactive metal will corrode first
> protects the less reactive metal from rusting
Ex: using zinc bars on the side of steel ships
> zinc more reactive than iron
> Zn -> Zn2+ + 2e-
Explain galvanizing (using example)
Iron protected by coating it with a layer of zinc
> electroplating or dipping in molten zinc
> ZnCO3 is formed when zinc reacts with O2 and CO2 in air
-> protects the iron by BARRIER METHOD
If coating damaged -> still protected but sacrificial protection
