Metals Flashcards
Describe the general physical and chemical
properties of metals
Physical: - Lustrous, shiny - Sonorous - Ductile - Malleable Chemical: - Conductor of heat and electricity - High density and melting point
Explain why metals are often used in the form of
alloys
An alloy is a mixture of metal or a mixture of metals with a non-metal. By making metal into an alloy, it becomes stronger and harder. This is because the layers if metal atoms in the alloy cannot slide over one another easily
Order of reactivity series
K Na Ca Mg Al C Zn Fe Pb H Cu Ag Au - Only metals above hydrogen react with HCl and and water or steam
Explain reactivity
- A more reactive metal displaces a less reactive metal from a solution of its salts
- The more reactive a metal is, the more easily it is to lose its valency electrons
- It is easier to lose electrons from the outer shell if :
+ there are many shells in between -> valency electrons are further away from the pull of nucleus
+ fewer protons in nucleus
Deduce an order of reactivity from a given set of
experimental results
Reduction of metal oxides with carbon
Carbon is placed between Al and Zn.
- Only oxides below of the metals below carbon can be reduced to the metal by heating with carbon.
- Metals more reactive than carbon have to be extracted by electrolysis
Account for the apparent unreactivity of
aluminium
the oxide layer which adheres to the metal
it is 0.0002 cm thick but enough to make metal resistant to corrosion
Describe the action of heat on the hydroxides and nitrates of the listed metals
- The more reactive the metal, the more stable its nitrate, hydroxide is
- Metal hydroxides decompose to metal oxide and water
- Alkali metal nitrates decompose to nitrite and oxygen
- Other metal nitrates decompose to metal oxide, nitrogen dioxide and water
Describe the ease in obtaining metals from their
ores by relating the elements to the reactivity series
- Metal oxides below carbon in the reactivity series are reduced by carbon when heated
- Above then extract by electrolysis
Name the uses of aluminium
– in the manufacture of aircraft because of its
strength and low density
– in food containers because of its resistance to
corrosion
Name the uses of zinc
-galvanising (protect steel from rusting) and for making brass
Describe the idea of changing the properties of iron
Are changed by adding controlled amounts of other metals or carbon to make steels
Name the uses of mild steel and stainless steel
Mild steel: 0.25% carbon. Soft. Malleable. Ductile. Make car bodies and machinery parts
Stainless steel: 20% chromium, 70% iron, 10% nickel. Strong, resist corrosion. Construction of pipes, cutlery- knives, forks, spoons, surgical instruments
Name the uses of copper related to its properties
- Used for electrical wiring because of its high electrical conductivity. Also malleable and ductile => can easily be shaped
- Conductor of heat => cooking pans
Describe the conversion of iron into steel using basic
oxides and oxygen
- Molten iron and scrap iron are poured in
- Water-cooled/oxygen lance is lowered into the converter
- Oxygen and calcium oxide are blown on the surface of molten iron
- Oxygen oxidises carbon, sulfur, silicon and phosphorus to their oxides: Si + O2 -> SiO2 or 4P + 5O2 -> 2P2O5, carbon dioxide and sulphur dioxide escape the converter because they are gases
- Silicon oxides and phosphorus oxides are acidic: CaO + SiO2(I) -> CaSiO3(I)
- The amount of carbon in steel is controlled by the amount of oxygen blown into impure iron. Longer the oxygen blast => more carbon removed
Name the main ore of aluminium
bauxite
