Topic 7 - Metals Flashcards
Describe the structure of metals
Positively charged metal ions touching in regular lattice
Delocalised elections floating between
What are delocalised electrons?
The electrons that a metal has lost to become an ion. They just float around
Define metallic bonding
The electrostatic attraction between the positive metal ions and the delocalised electrons
Explain why metals conduct electricity
Because to conduct you need
• charged particles
• that are free to move
The delocalised electrons fit both of these criteria
Explain why metals are malleable
When force is applied to metals, the top layer of ions slide across the one underneath it, causing it to bend
Define alloy
A mixture of a base metal and alloying agents
Describe the two methods with which alloys can be made
1) swapping out some of the base metal atoms and replacing them with alloying agent atoms
2) jamming some alloying agent atoms between some of the base metal atoms
Explain why alloys tend to be harder than base metals
The alloying agent atoms in an alloy tend to be a different size to those of the base metals atoms, distorting the layers of metal atoms and so the layers slide less easily.
Name the reactivity series
K Na Li Ca Mg Al C Zn Fe Pb H Cu Ag
Describe the reactivity series
Potassium -> calcium: very reactive
Magnesium -> zinc: fairly reactive
Iron to silver -> not very reactive
Gold: not at all reactive
Describe metal + cold water reactions
There is only enough energy for one of the bonds to be broken
Metal + cold water -> metal hydroxide + hydrogen
Magnesium, zinc and iron won’t react much
Copper won’t react
Describe metal + steam reactions
There is enough energy to break both bonds
Element + steam -> element oxide + hydrogen
Copper won’t react
How to carry out metal + water reactions
Place the metal into a beaker of water and hold a burning splint close to the metal to test the gas given off
Which group are the alkali metals
Group 1
How to carry out metal + steam reactions
1) place some mineral wool soaked in water at the base of a test tube held horizontally
2) place a strip of metal half-way up the test tube
3) plug the test tube using a bung with a hole through the centre where u place a small plastic cylinder
4) beat the mineral wool and metal with Bunsen burners
5) the steam will react with the metal, producing hydrogen gas
6) test the hydrogen gas with a burning splint
Describe the alkali metals
- they have low melting and boiling points
- they are very soft and can be cut easily with a knife
- they have low densities
- they react quickly with water, producing hydroxides and hydrogen gas
- their hydroxides and oxides dissolve in water to form alkaline solutions
Describe the reaction between Lithium and water
Li (s) + H2O (l) -> LiOH (aq) + 0.5H2 (g)
- fizzing
- solid disappears
- moves on surface of water
Describe the reaction between Sodium and water
Na (s) + H2O (l) -> NAOH (aq) + 0.5H2 (g)
- faster
- fizzing
- solid disappears
- moves on the surface of the water
Describe the reaction between potassium and water
K (s) + H20 (l) -> KOH (aq) + 0.5H2 (g)
- fizzing
- solid disappears
- moves on surface of water
- lilac flame
Describe the reactivity trend of alkali metals
They get more reactive as the group descends, because as the group descends, the outermost electron is further away from the nucleus, meaning it’s attraction is weaker, and it is more easily lost.
This can be seen through their reactions with water and oxygen
What happens to metal carbonated thermally decompose when heated
They thermally decompose
Describe the general formula for thermal decomposition
heat
metal carbonate ——> metal oxide + CO2
What is a displacement reaction
When a metal and a dissolved compound react, they displace each other (but only if the metal is more reactive)
What are the reactions of displacement reaction
1) what is happening to the elements
2) what is happening to the compounds
What are metal ores
Metal compounds found in the earths crust
What do we use to displace metals from their ores?
ASK ABOUT THIS
Carbon/ carbon monoxide
Describe the general formula for carbon reduction
carbon + metal oxide -> metal + carbon dioxide
What type of reaction is a carbon reduction and why?
REDOX
- carbon is oxidised (gains oxygen)
- metal oxide is reduced (loses oxygen)
What is the reducing agent in carbon reduction?
Carbon
What is a reducing agent?
The substance which takes oxygen away from another
What is an oxidising agent?
The substance which gives away its oxygen
Describe the extraction of iron from haematite in a blast furnace
1) coke (porous form of carbon) combusts
C + O2 -> CO2
2) CO2 reacts with coke
CO2 + C -> 2CO
3) CO reacts with haematite
3CO + Fe2O3 -> 2Fe + 3CO2
4) Limestone is thermally decomposed
CaCO3 -> CaO + CO2
5) CaO reacts with impurities in haematite
CaO + SiO2 -> CaSiO3 (slag)
Describe the method for extracting aluminium from bauxite
Electrolysis
Positive aluminium is attracted to negative carbon electrode (cathode)
Negative oxygen is attracted to the positive carbon electrode (anode)
Describe aluminium
- light
- strong
- low density -> planes and bicycle frames
- conducts electricity and heat well
- resists corrosion -> drinks cans
- reacts very quickly with oxygen in the air to form a protective layer of aluminium oxide to stop any further reactions taking place
Describe copper
- malleable
- ductile
- resistant to corrosion
- conducts electricity and heat very well
- used in wires because of low resistance
- used to help construction
- used in heating systems because of speedy transfer of heat
Describe iron
- soft, easily shaped
- brittle
- corrodes easily (rusts)
- used for electromagnetic valves because it is magnetically soft, but most of it is turned into steel
- dense
- wrought iron is malleable -> used to make gates and railings
Describe steel
- low carbon steel is easily shaped and used for car body panels
- high carbon steel is hard and used for cutting tools
- stainless steel is resistant to corrosion and used for cutlery and sinks
What is rust?
Hydrated iron (iii) oxide Fe2•O3
The water is loosely bonded to the iron(III) oxide
It is a soft, crumbly solid which flakes off to leave more iron available to rust again p
What is the rust reaction
2Fe + 1.5O2 + H2O -> Fe2O3•H2O
What are the methods of preventing rust
1) coating
2) sacrificial protection
3) galvanising
Describe coating
- using either paint, oil, grease (for moving parts), or plastic (for stationary parts)
- the Fe3+ is separates from the O2 and the H2O
Describe sacrificial protection
- attach a block of more reactive metal (magnesium)
- when oxygen reacts with iron, magnesium displaced it
3Mg + Fe2O3 -> 3MgO + Fe
Describe galvanising
• coat (to protect Fe3+) with a thin layer of zinc (providing sacrificial protection if the coating is scratched)
What happens when sodium reacts with oxygen?
Forms a mixture of sodium oxide (Na2O) and sodium peroxide (Na2O2)
What happens when potassium reacts with oxygen?
Forms a mixture of potassium peroxide (K2O2) and potassium superoxide (KO2)
Why do more reactive metals displace less reactive ones from their oxide
They bond more strongly to the oxygen
Describe the relationship between temperature given off by displacement reactions and reactivity of metals
The more reactive the metal, the more temperature given off
Name some alloys
Brass (copper + zinc)
Bronze (copper + tin)
