C15: Using resources

Question 1

what is corrosion?

Answer 1

destruction of materials by chemical reactions with substances in the environement
- occurs on surface of metal e.g rusting

Question 2

how is corrosion prevented?

Answer 2

apply coating that acts as barrier
e.g
- painting
- greasing
- electroplating

Question 3

rusting chemical reaction?

Answer 3

Iron + Water + oxygen –> hydrated iron oxide
- need water and oxygen for rusting to occur

Question 4

what is sacrificial protection/galvanising?

Answer 4

• use more reactive metal to coat metal

e.g zinc is used to galvanise iron
- zinc will react with oxygen and carbon dioxide in air /protects iron from corrosion
- Zn –> Zn2+ + 2e-
- zinc loses electrons more easily than iron/ iron recieves these electrons so is reduced , not OXIDISED

Question 5

how does zinc react with water during the galvanising of iron?

Answer 5

• electrons donated by zinc react wit hydrogen in water producing hydrogen gas
• 2H+ +2e- –> H2

Question 6

uses of copper alloys?

Answer 6

BRONZE : alloy of copper/tin (used for electrical connectors)
BRASS : alloy of copper and zin (used for tools)

Question 7

uses of Gold Alloys?

Answer 7

alloys of silver, copper, zinc and gold used for Jewellrey
- othe metals add strength/toughness to gold

Question 8

uses/properties of aluminium alloys?

Answer 8

low density (used for aircraft)
strong
corrosion resistant

Question 9

uses/properties of steel alloys?

Answer 9

steel alloys normally mixtures of carbon/iron
- Low carbon steels are easily shaped - used for sheeting
- high carbon steels are hard - used for cutting tools
- stainless steels (have chronimum/nickel) are corrosion resistant - used for cutlery

Question 10

how are glass ceramics made?

Answer 10

soda lime glass: made by heating a mixture of sand, sodium carbonate, limestone
- on cooling, it soldifies to form GLASS

Borosilicate Glass : MADE FROM SAND/BORON TRIOXIDE
- melts at higher temp than soda lime glass

Question 11

how are clay ceramics made?

Answer 11

shaping wet clay and heating in a furnace
-used as pottery or bricks –> strong so withsatnd weight/pressure

Question 12

properties of poylmers and uses?

Answer 12

• good electrical/heat insulators, so good for insulating electrical wiring

Question 13

how can the same monomer make same polymer with different properties?

Answer 13

• difference in manufacturing process

Question 14

how do the conditions to make
low density/high density polyethene differ?

Answer 14

LD : HIGH pressure, Moderate temp (low forces of attractions/chains further apart –> low MP/soft)
HD : low temps /pressure , with catalyst (high forces of attrcation/chains closer tgt –> High Mp)

Question 15

what are thermosoftening polymers?

Answer 15

induvidual chains entwinned with eachother , with WEAK intermolecular forces holding polymer chains tgt
- LOW MP / can be remoulded

Question 16

what are thermosetting polymers?

Answer 16

strong cross links between monomers on different polymer chains
- strong/rigid - dont melt

Question 17

what are composites made of and eg?

Answer 17

matrix/ reinforcement
- steel reinforced concrete
( steel - reinforcement , concrete-matrix)

Question 18

purpose of haber process?

Answer 18

• used to manufacture ammonia , which is used for fertilisers

Question 19

how are the raw materials for haber process obtained?

Answer 19

NITROGEN : - from air
HYDROGEN : - from natural gas

Question 20

haber process?

Answer 20

• PURIFIED gases are passed over IRON catalyst at 450 degrees/ 200atm
• some hydrogen/nitrogen react to from ammonia
• on cooling, ammonia liqufies and is removed
• remianing nitrigen/hyrdrogen are recycled

Question 21

what are ideal conditions for haber process/why are they not used?

Answer 21

IDEAL: N2 + 3H2 –> 2NH3
- high pressure –> equilibrium moves right (less molecules on right) –> more ammonia
- low temps –> FORWARD REACTION IS EXO , so will favour exothermic reaction –> more ammonia

but low temps lead to slow reaction rate/ high pressure needs to much energy

Question 22

what are NPK fertilisers?

Answer 22

formulatios containing correct ratios of nitrogen, phosphorous, potassium

Question 23

what salts are used for fertiliers?

Answer 23

Ammonium NITRATE
Calcium PHOSPHATE
POTASSIUM nitrate/sulfate

Question 24

how can ammonia be used to form ammonium nitrate?

Answer 24

ammonium salts : AMMONIA IS ALKALINE
- neutralises acids forming salts/water

nitric acid : AMMONIA UNDERGOES OXIDATION forming nitric acid

ammonia + nitric acid –> ammonium nitrate
- alkali +acid –> salt

Question 25

how is potassium nitrate/ sulfate obtained ?

Answer 25

from phosphate rocks

Question 26

what other salts are used to treat phospate rocks ?

Answer 26

nitric acid : CALCIUM Nitrate + phosphoric acid
- phosphoric acid is neutralised with ammonia to form ammonium phosphate
sulfuric acid: calcium phosphate/sulfate
- single super phosphate
phosphoric acid - calcium phosphate - triple super phosphate

all used to give phosphorous, nitrogen for fertilisers

Question 27

Why can’t phosphorous rocks be used as fertilisers directly?

Answer 27

Not soluble in water

Question 28

REQUIRED PRACTICAL: making ammonium sulfate

Answer 28

1) collect 25cm cubed ammonia solution using pippete in conical flask
2) add dilute sulfuric acid , 1cm cubed at a time from burette ( keep swirling)
3) drop small piece of blue litmus in spotting tile and add solution until it goes pink
4) repeat titration until reach 2 concordant results
5) pour solution in evaporating dish /heat over water bath until half of water from solution is evaporated
6) leave rest to evaporate off slowly - leaving crystals
7) pat dry with filter paper

Question 29

Compare production of fertiliser in lab to industry?

Answer 29

LAB : - made small ‘batch’
- uses glass appartus
- use dilute reactants

FACTORY : - concentrated reactants at 60 degrees
- stainless steel vessels/pipework (withstand high pressure/corrosion
- continuous process

Question 30

required practical : chromatography

Answer 30

1. Use a ruler to draw a horizontal pencil line 2 cm from the end of the chromatography paper
2. Use a different capillary tube to put a tiny spot of each colouring A, B, C and D on the line
3. Use the fifth tube to put a small spot of the unknown mixture U on the line
4. Make sure each spot is no more than 2-3 mm in diameter and label each spot in pencil
5. Pour water into the beaker to a depth of no more than 1 cm and clip the top of the chromatography paper to the wooden spill.
6. Carefully rest the wooden spill on the top edge of the beaker. The bottom edge of the paper should dip into the solvent
7. Allow the solvent to travel undisturbed at least three quarters of the way up the paper
8. Remove the paper and draw another pencil line on the dry part of the paper as close to the wet edge as possible. This is called the solvent front line
9. Measure the distance in mm between the two pencil lines. This is the distance travelled by the water solvent
10. For each food colour A, B, C and D measure the distance in mm from the start line to the middle of the spot

Question 31

required practical : analysing purification of water samples

Answer 31

1. Use the universal indicator paper to
   determine the pH of the water sample
2. Accurately weigh an empty evaporating basin to two decimal places
3. Add 25 cm3 of water sample A into the evaporating basin
4. Heat the evaporating basin on a tripod and gauze using a Bunsen burner until the solids start to form and the majority of water has evaporated
5. Leave for the remaining water to evaporate off
6. Weigh the cooled evaporating basin again and calculate the mass of the solids that were dissolved in the water.