C15

Question 1

rusting of iron

Answer 1

• both oxygen and water are needed for iron to rust
• providing a barrier protects it from rusting

Question 2

preventing rust

Answer 2

coating iron with:
- paint
- oil or grease
- plastic
- less reactive metal
- more reactive metal

Question 3

sacrificial protection

Answer 3

provides protection against rusting even when iron is exposed to water and air
Iron needs to be attached to a more reactive metal (zinc)

Question 4

alloys

Answer 4

harder than pure metals because the regular layers in a pure metal are distorted by differently sized atoms in an alloy

Question 5

copper alloys

Answer 5

Bronze is made by mixing copper with tin

Question 6

aluminium alloys

Answer 6

alloyed with other elements to make it harder

Question 7

gold alloys

Answer 7

alloyed with copper to make jewellery

Question 8

steels

Answer 8

pure iron is too soft so its alloyed with carbon to make it harder

Question 9

carbon steels

Answer 9

carefully controlled quantities of carbon and other elements are added to iron to make steel alloys with different properties.

Question 10

examples of steels

Answer 10

• high carbon steels, which are very hard but brittle
• low carbon steels, which are soft and easily shaped
• stainless steels, which are resistant to corrosion

Question 11

monomers

Answer 11

monomers affect the properties of the polymers that they produce

Question 12

reaction conditions

Answer 12

changing reaction conditions can change the properties of the polymer produces

Question 13

low density polyethene

Answer 13

• using high pressures and trace of oxygen ethenes form LD polyethene
• polymer chains cannot pack closely together

Question 14

high density polyethene

Answer 14

• using catalyst at 50 degree and raised pressure ethene makes HD polyethene
• straight polymer chains pack closely together

Question 15

thermosoftening

Answer 15

thermosoftening polymers will soften or melt easily when heated because their intermolecular forces are weak

Question 16

thermosetting

Answer 16

thermosetting polymers will not soften because of their strong covalent bonds between chains

Question 17

glass

Answer 17

• soda glass is mad by heating a mixture of sand, limestone and sodium carbonate
• Borosilicate glass is made from sand and boron trioxide and melts at a higher temp than soda glass

Question 18

ceramics

Answer 18

• made by shaping clay and heating in a furnace
• ions and atoms arranged in giant structures that form layers

Question 19

composites

Answer 19

made of two materials with one material acting as a binder for the other material improving desirable property that neither materials could offer alone

Question 20

composite example

Answer 20

concrete - made from sand, cements and gravel mixed with water to make a hard, strong composite

Question 21

materials needed for production of ammonia

Answer 21

• nitrogen from air
• hydrogen from natural gas (methane)
• nitrogen + hydrogen -> ammonia

Question 22

the harbour process

Answer 22

• turns nitrogen into ammonia
• ammonia is removed by cooling the gases so ammonia liquifies
• its separated from the unreacted nitrogen and hydrogen gas
• gas recycled by recompressing and heating then returning to reaction vessel

Question 23

effect of changing temp

Answer 23

• increase, it favours the endothermic reaction
• decrease, it favours the exothermic reaction

Question 24

effect of changing gas pressure

Answer 24

• increase, favours the side with less molecules
• decrease, favours the side with more molecules

Question 25

effect of changing conc.

Answer 25

increase equilibrium would move to the right

Question 26

effect of catalyst

Answer 26

increases the rate of reaction for both sides equally

Question 27

dynamic equilibrium

Answer 27

as the forward and reverse reactions are continuously taking place a state of dynamic equilibrium has been reached

Question 28

reversible reactions

Answer 28

the products of the reaction can react to make the original reactants

Question 29

le Chatelier's principle

Answer 29

- when change in conditions is introduced to a system at equilibrium the position shifts to cancel out the change

Question 30

ammonia and fertilisers

Answer 30

- ammonia is used to make nitric acid - nitric acid made can be reacted with more ammonia to make ammonium nitrate fertiliser

Question 31

neutralisation of ammonia

Answer 31

neutralised by sulfuric acid to make ammonium sulphate fertiliser and with phosphoric acid to make ammonium phosphate fertiliser

Question 32

NPK fertilisers

Answer 32

nitrogen, phosphorus and potassium in mixtures of compounds called NPK

Question 33

Phosphorus

Answer 33

from phosphorus rock mined and treated with acids to form fertilisers - ammonium phosphate - calcium phosphate

Question 34

potassium

Answer 34

comes from potassium salts mined from the ground for use as fertilisers - potassium chloride - potassium sulphate