Ch15 Using our resources

Question 1

Corrosion

Answer 1

destruction of materials by chemical reactions with substances in the environment

Question 2

Rusting

Answer 2

corrosion of iron
oxygen and water are necessary for it to take place
iron + oxygen + water -> hydrated iron(III) oxide

Question 3

Preventing rust

Answer 3

coating the iron with a barrier:

grease/oil
plastic
electroplating
paint

Question 4

Aluminium rusting

Answer 4

doesn’t happen

- has an aluminium oxide coating that protects the metal from corroding

Question 5

Using a more reactive metal to prevent rusting

Answer 5

molten metal or electroplating
example- zinc is used to galvanise iron
zinc reacts with oxygen instead, losing electrons and becoming oxidised
sacrificial protection

Question 6

Copper alloys

Answer 6

Bronze -> copper + tin

Brass -> copper + zinc

Question 7

Aluminium alloy properties

Answer 7

low density
lightweight but strong
- used to build aircraft
- used as armour plating on military vehicles

Question 8

Bronze uses

Answer 8

toughness and resistance to corrosion
used for
- statues and decorative items
- ship propellers

Question 9

Brass uses

Answer 9

hard
can be hammered into shapes and pressed into intricate shapes
used for
- musical instruments
- door fittings and taps

Question 10

Gold alloys

Answer 10

usually alloyed with copper, silver and zinc to make jewellery
proportion of gold in the alloy is measured in carats
24 carat being 100% pure gold

Question 11

Steel

Answer 11

alloy of iron + carbon and other metals

Question 12

low- carbon steels

Answer 12

removing carbon from the iron obtained from a blast surface
soft and easily shaped
used in machinery

Question 13

high-carbon steel

Answer 13

strong but brittle

Question 14

nickel-steel alloy

Answer 14

resistant to stretching forces

used for drill bits

Question 15

stainless steels

Answer 15

chromium + nickel
hard
resistant to corrosion
used for cooking utensils and reaction vessels

Question 16

thermosoftening polymers

Answer 16

soften easily and then re-set when they cool down
made up of individual polymer chains tangled together
easy to separate
weak intermolecular forces

Question 17

thermosetting polymers

Answer 17

don’t melt when heated
have strong covalent bonds forming ‘cross-links’ between polymer chains
rigid
don’t soften

Question 18

properties of polymers depend on…

Answer 18

monomers used to create it

conditions chosen to carry out the reaction

Question 19

low density poly(ethene)

Answer 19

made from ethene monomers
uses high pressure and a trace of oxygen
polymers are randomly branched and cannot pack closely together

Question 20

high density poly(ethene)

Answer 20

made from ethene monomers
uses a catalyst at 50°C at a slightly raised pressure
straight chains
packed closer
higher softening temp 
stronger

Question 21

Soda- lime glass

Answer 21

made by heating a mixture of sand, limestone and sodium carbonate
random arrangement of particles

Question 22

Borosilicate glass

Answer 22

made from sand and boron trioxide
melts at high temperatures than soda-lime glass
used for ovenware

Question 23

Ceramics

Answer 23

made from shaping wet clay
- made from aluminium and potassium
- silicon and oxygen
heated in a furnace so the water evaporates and strong bonds form between layers

Question 24

Ceramic properties

Answer 24

brittle

• sharp blow distorts layers in structure
• ions with like charges repel each other, cracking the ceramic object

Question 25

composites

Answer 25

made of two materials

has improved properties

Question 26

reinforcement

Answer 26

a matrix(a binder) of one material surrounding and binding together fibres or fragments of the other material

Question 27

examples of composites

Answer 27

concrete

• cement, sand and gravel mixed with water
• very hard
• strong in compression
• can be set around matrix of steel rods

plywood
- thin sheets of wood glue together with successive layers of grain at right angles

Question 28

Haber process

Answer 28

• nitrogen in the air
• hydrogen from methane

1. gases are purified
2. passed over an iron catalyst at high temp(450°C) and high pressure(200 atmospheres)
3. some hydrogen and ammonia react to form ammonia
   N2 + 3H2 -> 2NH3
4. ammonia is then removed- cooling the gases so the ammonia liquifies and is then separated from the unreacted N and H gas which have higher bp
5. unreacted hydrogen and nitrogen are recycled back into the reaction mixture

Question 29

Haber reversible reaction

Answer 29

ammonia gas breaks down into hydrogen and nitrogen

Question 30

NPK fertilisers

Answer 30

plants need nitrogen to grow(make proteins)
- have to use Haber process to change nitrogen gas into ammonia because plants can only absorb soluble form
phosphorous
potassium

Question 31

making hydrogen for Haber process

Answer 31

methane + steam -> hydrogen + carbon monoxide

at very high temp

Question 32

making nitrogen for Haber process

Answer 32

fractional distillation of liquid air (cooled to -200°C)

Question 33

Economics of Haber process

Answer 33

energy cost to liquefy and compress air
costs for heating water
methane gas is expensive

Question 34

maximum yield of ammonia

Answer 34

make pressure high as possible to shift
(volume of reactants > vol of products)

decreasing temp
-slower rate of reaction(expensive)

iron catalyst

Question 35

phosphorous treated with nitric acid

Answer 35

produces phosphoric acid and calcium nitrate

phosphoric acid is then neutralised with ammonia to produce ammonium phosphate

Question 36

phosphorous treated with sulfuric acid

Answer 36

produces superphosphate

- mixture of calcium phosphate and calcium sulfate

Question 37

phosphorous rock treated with phosphoric acid

Answer 37

produces triple superphosphate

- calcium phosphate

Question 38

sources of potassium

Answer 38

potassium sulfate and potassium chloride mined from the ground

Question 39

fertilisers

Answer 39

1. ammonia + phosphoric acid -> ammonium phosphate
2. ammonia + sulfuric acid -> ammonia sulfate
3. ammonia + nitric acid -> ammonium nitrate