Metals Flashcards
Properties of metals
- Usually solid at room temp (high melting and boiling points
- Shiny and easily workable
- GOOD CONDUCTORS OF ELECTRICITY AND HEAT
- Form positive ions in their compounds
- HAVE OXIDES THAT ARE USUALLY BASIC, reacting with acids to give a salt and a water
Properties of non-metals
- Low melting and boiling points (except silicon and carbon)
- Brittle as solids, not the same shine as in metals
- DON’T USUALLY CONDUCT ELECECTRICITY (EXCEPT SILICON AND CARBON)
- POOR CONDUCTORS OF HEAT
- Tend to form negative ions and covalent compounds
- HAVE OXIDES WHICH ARE ACIDIC OR NEUTRAL
Reactivity series of metals
- Potassium
- Sodium
- Lithium
- Calcium
- Magnesium
- Aluminium
- (Carbon)
- Zinc
- Iron
- (Hydrogen)
- Copper
- Silver
- Gold
Metallic crystals
Metals have a giant, 3D lattice structure where positive ions are arranged in a regular pattern in a ‘sea of electrons’.
- The outer shell (valence) electrons are detached from the atoms and are DELOCALISED/ spread out throughout the structure.
- They are good conductors of electricity because the delocalised electrons are free to move when voltage is applied to the metal.
- They are malleable and ductile- the layers of positive ions slide over one another and take up different positions (electrons move with them so bonds aren’t broken)
Extraction of metals
How a metal is extracted partly depends on its position in the reactivity series.
Extraction: Metals less reactive than zinc
IRON AND COPPER
The cheapest way of reducing the ore is to heat it with carbon or carbon monoxide. Carbon is cheap and can also be used as a source of heat, as with iron in a blast furnace.
Extraction: Metals more reactive than zinc
They are usually produced by electrolysis, where metals’ ions are given electrons at the cathode. This is expensive, so metals like aluminium are more expensive than iron.
Extraction- other methods
Some metals like titanium are extracted by heating the compound with a more reactive metal. This is also expensive as you need the reactive metal to be extracted as well.
The rusting of iron
Iron rusts with oxygen and water, and is accelerated by electrolytes such as salt.
Rust
Fe2O3·nH2O, where n is a variable number. It behaves as a mixture of iron (lll) oxide and water.
Preventing iron from rusting: Barriers
-Paint/ oil/ grease coating
-Covering it in paint
PROBLEM: Once the coating breaks, it rusts.
Preventing iron from rusting: Alloying iron
Mixing iron with chromium and nickel to make stainless steel.
It is expensive but effective.
Preventing iron from rusting: Sacrificial metals
It can be coated with zinc to make galvanised iron, because zinc is more expensive so it corrodes instead. Zinc loses electrons in this process and they go to the iron- if it can’t form ions, it can’t rust!
Zn(s) –> Zn2+ + 2e-
Extraction of iron from iron ore in a blast furnace: Materials to go in
Iron ore, coke (impure carbon) and limestone goes in, called charge. The limestone (CaCO3 is there to remove impurities.
C + O2 –> CO2
To make Carbon dioxide, which is needed later, and to generate heat- it is a very exothermic reaction. The oxygen comes from the hot air blasted in.
CO2 + C –> 2CO (reducing CO2)
To generate the reducing agent of CO2, Carbon monoxide
Fe2O3 + 3CO –> 2Fe + 3CO2
To make iron in a redox reaction. The carbon dioxide is then recycled to the top of the blast furnace.
Cast iron
4% carbon, brittle and very hard
Used for manhole covers, guttering and drainpipes and cylinder blocks in car engines.
Mild iron
0.25% carbon, hard and strong
Used for wire, nails, car bodies, ship building, girders and bridges
Wrought iron
Pure iron, soft and weak
Used to be used for decorative gates and railings. Never structural.
High-carbon steel
1.5% carbon, brittle and hard
Used for masonry nails
Stainless steel
An alloy with chromium and nickel to form strong oxide layers, resistant to corrosion.
Extraction of aluminium from purified aluminium oxide
Because aluminium is fairly reactive, it is extracted using electrolysis. Aluminium oxide has a very high melting point and it isn’t practical to electrolyse molten aluminium oxide. Instead, it is dissolved in molten CRYOLITE. Cryolite is another aluminium compound that melts at a more reasonable temperature, around 1000C
Extraction of aluminium from purified aluminium oxide: Conditions
The cell operates at about 5-6 volts but with 100,000 amps. The heat generated by the current keep the electrolyte molten. The anodes have to be replaced regularly because at the high temperature the carbon anodes react and form CO2.
Extraction of aluminium from purified aluminium oxide: Cell
There is a carbon lining the container as the cathode.
There are carbon anodes as rods.
The steel tank is lined to be heat resistant.
Molten aluminium collects at the bottom, at the cathode.
Extraction of aluminium from purified aluminium oxide: Equations
CATHODE: Al3+(l) + 3e- –> Al(l)
ANODE: 2O2-(l) –> O2(g) + 4e-
Aluminium
It is not very strong so alloys are usually used instead, like silicon, copper or magnesium. It is low density, strong (when alloyed), a conductor of electricity and heat, shiny appearance and has an ability to resist corrosion.
It is used in wire cables, saucepans and engines.
Burning Magnesium
2Mg(s) + O2(g) –> 2MgO(s)
Bright white flame- though brighter in pure O2.
Makes a white, powdery ash of magnesium oxide.
Metals reactions with water/ steam
Metals above hydrogen in the reactivity series react with water or steam to produce hydrogen. Metals below hydrogen don’t react.
Metals with steam
Metal + Steam –> Metal oxide + Hydrogen
Metals with cold water
Metal + Cold water –> Metal hydroxide + Hydrogen
Water with Sodium, Potassium and Lithium
Sodium, Potassium and Lithium are alkali metals so fizz on top of the surface of the water violently.
2x(s) + 2H2O(l) –> 2xOH(aq) + H2(aq)
Water with Calcium
Calcium reacts gently, a warm mixture forming an insoluble Calcium hydroxide.
Ca(s) + 2H2O(l) –> Ca(OH)2 + H2(g)
Steam with Magnesium
There is almost no reaction here, Magnesium becomes coated with insoluble Magnesium hydroxide when it is with steam in a boiling tube and mineral wool soaked in water.
Mg(s) + H2O(g) –> MgO(s) + H2(g)
Steam with Zinc and Iron
Zinc and Iron reacts with steam, slowly producing hydrogen that can be collected.
Zn(s) + H2O(g) –> ZnO(s) + H2(g)
3Fe(s) + H2O(g) –> Fe3O4(s) + 4H2(g)
Metal Oxide
Acid + Metal Oxide –> Salt + Water
Metal (above hydrogen) + Steam –> Metal Oxide + Hydrogen
- Mostly insoluble in water and they don’t react
- Though a very small amount does react with water and forms a slightly alkaline solution
Metal Hydroxide
Acid + Metal Hydroxide –> Salt + Water
Metal (above hydrogen) + Cold water –> Metal Hydroxide + Hydrogen
Metal Carbonate
Acid + Metal Carbonate –> Salt + Water + Carbon Dioxide
