C15 - Rusting

Question 1

corrosion

Answer 1

caused y chemical reactions between metal and substances in the environment
- destruction of material
- effects strength

Question 2

rusting

Answer 2

corrosion of iron
-becomes soft, crumbly, flakes off

Question 3

oxide layer of aluminium

Answer 3

-protects it from further corrosion

Question 4

what is needed for iron to rust

Answer 4

both air and water

Question 5

rust chemical formula

Answer 5

hydrated iron oxide
-water loosely bonded in structure
-iron + water + o2

Question 6

prevention of rust

Answer 6

coat with:
- paint
-oil/grease
- plastic
-less/more reactive metal

Question 7

sacrificial protection or electroplating elements

Answer 7

-zinc, mg, al for iron

Question 8

sacrificial protection or electroplating process

Answer 8

-iron is galvanised (protected)
-reacts with water/o2 instead

Question 9

why is zinc used in electroplating

Answer 9

zinc = more reactive and better reducing agent

Question 10

electroplating used on

Answer 10

-equipment under sea
- where coating may be scratched

Question 11

why are alloys harder than pure metals

Answer 11

• regular layers in a pure metal are distorted by differently sized atoms in alloy

Question 12

bronze

Answer 12

alloy of copper + tin
-tough
-resists corrosion
-statues

Question 13

brass

Answer 13

-alloy of copper + zinc
- musical instruments

Question 14

aluminium alloys

Answer 14

• low density
• aircraft

Question 15

why are pure metals alloyed

Answer 15

to make them harder
- pure iron = too soft to be useful

Question 16

gold in jewellery

Answer 16

• alloy of silver,copper, zinc

Question 17

carat

Answer 17

proportion of gold in alloy is measured in this
-24 = 100%
- 18 = 75%

Question 18

steel

Answer 18

allows of iron and carbon and other metals
-added to change properties

Question 19

carbon steels - high carbon properties

Answer 19

• strong but brittle

Question 20

low carbon steel properties

Answer 20

softer
easily shaped

Question 21

stainless steels

Answer 21

• contain chromium and nickel
• hard + resists corrosion

Question 22

stainless steels eg

Answer 22

• cutlery
  -pipework

Question 23

nickel steel alloy eg

Answer 23

bridges
-bicycle chains

Question 24

properties of polymer depends on

Answer 24

monomers affect this
- changing reaction conditions

Question 25

HD and LD poly(ethene)

Answer 25

made from ethene

Question 26

thermosoftening polymers

Answer 26

-soften easily
- re set when cooled
- made from individual polymer chains that are tangled
-can be remoulded

Question 27

thermosoftening polymers - soften easily?

Answer 27

weak intermolecular forces

Question 28

thermosoftening polymers - re set when cooled?

Answer 28

• intermolecular forces bring polymer molecules back

Question 29

Thermosetting polymers

Answer 29

-don’t melt
- fixed together by strong covalent bonds
-form cross links between polymer chains
-don’t separate

Question 30

thermosetting polymers heated highly

Answer 30

will char not melt

Question 31

soda lime glass

Answer 31

made by heating sand, sodium carbonate, limestone
-form random arrangement when cooled

Question 32

Borosilicate glass

Answer 32

made from glass + boron trioxide
- higher melting point than soda lime
-use = ovenware

Question 33

clay ceramics eg

Answer 33

-pottery and bricks

Question 34

ceramics

Answer 34

made by shaping wet clay
-heating in furnace
-hard but brittle

Question 35

Composites

Answer 35

made of 2 materials
-one as binder for other

Question 36

composites - binder

Answer 36

binds fibres of other material
-reinforcement process

Question 37

purpose of composites

Answer 37

improves desirable properties that neither original material could offer alone

Question 38

ceramics + polymers prop

Answer 38

• tough
  -flexible
• eg fibreglass (kayak)

Question 39

examples of composites

Answer 39

plywood - thin sheets glued together
concrete - hard and strong in compression

Question 40

concrete materials

Answer 40

cement
sand
gravel
water

Question 41

plywood pros

Answer 41

prevents splitting along grain