C9.1 Flashcards
Why is aluminium used in aircraft’s
Low density
Why is aluminium used in overhead cables
Because of its low density and good conductivity
Why is aluminium used in food containers
Because of its resistance to corrosion
Why is copper used in electrical wiring
Good electrical conductivity
Chemical properties of metals
a) React with acids to form hydrogen gas and salts
b) reacts with water to give hydroxide or oxide with steam
c) metals form oxides
d) form alloys
Physical properties of metals
Thermal conductivity
Electrical conductivity
Malleability
Ductility
Melting and boiling points
What is an alloy and give an example
Mixture of elements (metals) to form a stronger metal (different sized atoms)
Eg brass is a mixture of zinc and copper
Why are alloys stronger
Because of their different sized atoms making it harder to be bent or deform. Disrupts the regular arrangement of atoms. Different sized atoms can no longer slide over each other
Why is stainless steel more useful than iron
Stainless steel is more resistant to rust
What is the order of the reactivity series
Potassium, sodium, calcium, magnesium, aluminium, (carbon) zinc, iron, hydrogen, copper, silver, gold
What is the reaction of potassium with water and give a balanced equation
The potassium reacts vigorously with water and forms potassium hydroxide and give hydrogen gas off
K + H₂O → KOH + H₂
Magnesium reaction with steam
Produces magnesium oxide and hydrogen gas
Mg + H₂O → MgO + H₂
Zinc and hydrochloride acid
Zinc displaces the hydrogen to give zinc chloride and hydrogen gas
Zn + 2HCl → ZnCl₂ + H₂
What conditions are needed for iron to rust
Oxygen and water
Corrosion barrier methods for iron
Painting, greasing or oiling and coating with plastic
How do the barrier methods prevent rusting
They keep a protective layer from the water/ air being in contact of the iron
How is zinc used to keep iron from rusting and what is the name of the technique
The technique is called galvanising and sacrificial protection. It is used because zinc is more reactive than iron so when zinc is placed on the hull of the boat, the zinc rusts before the iron making this technique effective
