Metals Flashcards
What are the 4 properties of metals
- High melting and boiling points (EXCEPTIONS eg. gallium, mercury)
Due to strong metallic bonds holding the positive metallic ions and sea of electrons together - Have high densities (EXCEPT group 1 metals)
- Good conductors of heat and electricity*
Due to free mobile electrons within solid structure - Are malleable and ductile
Due to layers of atoms that can slide over each other easily due to orderly arrangement
What is an alloy?
It is a mixture of a metal and one or more elements
How does adding another element to a metal (becomes an alloy), makes it harder and stronger?
Atoms of the added elements are of a different size.
These added atoms DISRUPT the ORDERLY arrangement of the metal atoms, PREVENTING the layer of atoms from sliding past each other easily when a force is applied.
What are the various reactions of the metals of the reactivity series reacting with water/steam?
K reacts VERY VIOLENTLY with cold water,
2K (s) +2H^2O (l) -> 2KOH (aq) +H^2 (g)
Na reacts VIOLENTLY with cold water,
2Na (s) +2H^2O (l) -> 2NaOH (aq) +H^2 (g)
Ca reacts READILY with cold water, rapid effervescence
Ca (s) + 2H^2O -> Ca(OH)2 (aq) + H^2
Mg reacts VERY SLOWLY with cold water/reacts VIOLENTLY with steam
(cold water) Mg (s) + 2H^2O (l) -> Mg(OH)2 (aq) + H^2 (g)
(steam) Mg (s) + H^2O (g) -> MgO (aq) + H^2 (g)
Zn no observable reaction with water, hot zinc reacts READILY with steam
Zn (s) + H^2O (g) -> ZnO (aq) + H^2 (g)
Cu no reaction
Fe no observable reaction water, red-hot iron reacts slowly with steam
3Fe (s) + 4H^2O (g) -> Fe3O4 (s) +4H^2 (g)
What are the various reactions with HCl?
K reacts EXPLOSIVELY,
2K (s) + 2HCl (aq) -> 2KCl (aq) +H2 (g)
Na reacts EXPLOSIVELY,
2Na (s) + 2HCl (aq) -> 2NaCl (aq) +H2 (g)
Ca reacts VIOLENTLY, rapid effervescence
Ca (s) + 2HCl (aq) -> CaCl2 (aq) +H2 (g)
Mg reacts RAPIDLY, rapid effervescence
Mg (s) + 2HCl (aq) -> MgCl2 (aq) +H2 (g)
Zn reacts MODERATELY FAST, effervescence
Zn (s) + 2HCl (aq) -> ZnCl2 (aq) +H2 (g)
Fe reacts SLOWLY, effervescence, pale green aqueous iron(II) chloride obtained
Fe (s) + 2HCl (aq) -> FeCl2 (aq) +H2 (g)
Cu no reaction
Explain and give an example of a displacement reaction of aqueous solutions
A more reactive metal will displace a less reactive metal from its SALT solution
Zn (s) + CuSO4 (aq) -> ZnSO4 (aq) + Cu
(Ionic) Zn (s) + Cu2+ (aq) -> Zn2+(aq) + Cu (s)
Explain and give an example of displacement of metal oxides
A more reactive metal is able to remove the oxygen from a less reactive metal OXIDE
Al (s) + Fe2O3 (s) -> Al2O3 (s) +Fe (l)
What metal oxides are reduced by carbon to become pure metals?
All metals below C in reactivity series;
Zn, Fe, Pb, Cu, Ag
What metal oxides are reduced by hydrogen to become pure metals?
Fe, Pb, Cu, Ag
IP(H)CA
Explain the relationship of thermal stability of metal carbonates
The more reactive the metal, the more stable is the carbonate, the harder it is for the carbonate to decompose.
K & Na unaffected
Ca, Mg, Zn, Fe, Pb, Cu decompose into metal oxide and carbon dioxide on heating
Ag decomposes into silver and carbon dioxide
Extractions of metals
Above Carbon in reactivity series, (electricity on molten)
K, Na, Ca, Mg, Al
Uses electricity to break up molten compounds
More reactive metals form stable compounds with strong ionic bonds,
Electricity can be used to break up the molten compound into its elements to obtain the metal.
Below Carbon in reactivity series (carbon on oxides)
Zn, Fe, Pb, Cu
Found as oxides or sulfides in nature, sulfides are heated in air to produce oxides first,
oxides are heated with carbon (reducing agent) to obtain metal
OR
Using hydrogen, to reduce iron and below eg. lead, copper (less reactive)
Silver & Gold, found as element
What are the 4 raw materials used in extraction of iron?
- Iron ore/ haematite (Fe2O3)
- Limestone/ calcium carbonate (CaCO3)
- Coke/ Carbon
- Hot air (fed from bottom of furnace)
What are the 4 steps & 5 reactions in a blast furnace?
- Carbon dioxide is produced,
C (s) + O2 (g) -> CO2 (g)
2.Carbon monoxide is produced
C (s) + CO2 (g) -> 2CO (g)
- Haematite is reduced to iron
Fe2O3 (s) +3CO (g) -> 2Fe (l) +3CO2 (g) - Impurities are removed
CaCO3 (s) -> CaO (s) +CO2 (g) - Calcium oxide reacts with silicon dioxide to form slag
CaO (s) + SiO2 (s) -> CaSiO3 (l)
Mild/ low carbon steel VS high carbon steel
Low carbon steel
- 0.25% carbon
- Strong but malleable
- Different sized carbon atoms disrupt the regular layers of iron atoms, hence conferring strength
- Used in car bodies and machinery
High carbon steel
- 0.45-1.5% carbon
- Stronger but brittle
- Too much disruption of layers, when force is applied, metal fractures
- Used in knives, chisels, saws, cutting tools
Define rusting/corrosion
Exothermic reaction that requires oxygen and oxygen.
Rusting only happens in iron/steel, other metals CORRODE
What speeds up rusting?
- Presence of dissolved ionic particles eg. carbon dioxide or sulfur dioxide in water or droplets of dissolved sodium chloride in air
- When iron or steel is in contact with a less reactive metal eg. copper, tin
During rusting,
Iron loses electrons to the water/oxygen combination
Iron(II) ions formed are then oxidised by oxygen to form hydrated iron (III) oxide
What are the 3 methods of preventing corrosion
- Coating object with layer of substance
- Sacrificial protection
- Use of stainless steels/alloys
What are the different types of coating object with layer of substances and its uses-
PROTECTIVE LAYER SO IRON IS NOT EXPOSED TO WATER/OXYGEN
Painting - for cars, doors etc.
If paint is scratched, rusting will take place under painted surface
Oiling/greasing - Tools and machine parts
Protective film gathers dust and requires frequent reapplication
Tin-plating - Food cans
If tin surface is scratched, iron beneath it rusts MORE RAPIDLY as iron is more reactive than tin, iron loses electrons more readily than tin
Plastic coating - kitchenware eg. draining racks
If plastic layer is torn, iron starts to rust
Chrome-plating - taps/handlebars
Gives bright shiny finish
What are the different types of sacrificial protection and its uses?
Galvanising - for zinc roofs, kitchen sinks, dustbins
If surface is broken, zinc is more reactive than iron, it will lose electrons more easily, will corrode IN PLACE of iron, protects iron from rusting
Attaching metal blocks of zinc or magnesium - Underground pipes, ship hulls etc.
Zinc and magnesium will corrode IN PLACE of iron as they are more reactive
How does using stainless steel/alloys work
Stainless steel contains chromium and steel which do not rust
Used in cutlery, surgical instruments
What is a metallic bond?
A metallic bond is the force of attraction between positive metal ions and sea of mobile electrons
How is steel made from cast iron?
- Remove impurities by oxidation
- Cast iron is melted and poured into furnace
- Pure oxygen at high pressure is blown through molten cast iron
- Oxygen oxidises impurities
- Oxides are blown out or react with CaO to form calcium silicate (slag) CaSiO3
- Slag is poured off, pure/wrought iron remains - Alloying with carbon and other elements to make various types of steel
- Carbon and other elements stirred in right amounts to make various alloys
