1
Q
What is corrosion?
A
When chemical reactions with materials and the substances in the environment destroys them.
2
Q
What is rusting?
A
common type of corrosion that affects iron
3
Q
What is required for iron to rust?
A
Both air and water
4
Q
What are the materials required for the experiment to prove water and air are required for rusting?
A
- three test tubes
- three nails
- water
- drying agent (e.g. silica gel)
- oil
5
Q
Method for iron rusting:
A
Three test tubes:
1) nails, water, left open to air
2) nail, drying agent (absorb moisture from air), stopper in tube (prevents moisture from entering)
3) nail, boiled water removes removes dissolved air, sal with oil to prevent re-entering of air.
- leave tubes undisturbed for several days.
6
Q
Results of rusting experiment?
A
Tube 1: nail rusts (air and water present)
Tube 2: doesn’t rust (suggests absence of water causes rusting)
Tube 3: doesn’t rust (suggests absence of oxygen prevents rusting)
7
Q
How can we prevent corrosion with barriers?
A
- protective coatings: greasing, painting, electroplating
- Aluminium forms a protective oxide coating on its surface when exposed to air (barrier) that shield from further damage.
8
Q
How can we prevent corrosion with sacrificial protection? Example?
A
- metals coated with MORE REACTIVE metals
- more reactive metals corrodes instead of underlying metal
- e.g. zinc galvanises iron (if protective zinc is scratched, the zinc around the scratch will corrode instead of iron)
9
Q
What are alloys?
A
- mixture of metals
- provide improved properties compare to pure metals
- enhanced characteristics
10
Q
What is bronze + characteristics? Used to make wha?
A
- alloy of copper and tin
- harder than copper
- used to make medals/ statues
11
Q
What are gold alloys made from? How is its purity measured (what doess the purity show?)
A
- GOLD is used in jewellery but usually not pure
- alloyed with: sliver, copper, zinc
- purity (carats) shows shows PROPORTION OF GOLD in the alloy
12
Q
What are the carats and proportions of gold?
A
24 carat - 100% pure
18 carat - 75% pure
12 carat - 50% gold
6 carat - 25% gold
13
Q
What are steels?
A
- iron alloys with carbon
14
Q
Properties of steel?
A
- high carbon steel: strong but brittle
- low carbon steel: soft and malleable
- stainless steel: also includes chromium and nickel -> hard and resistant to corrosion
15
Q
What are aluminium alloys? Why is aluminium alloyed?
A
- aluminium mixed with other metals to make them stronger and suitable for use n things such as aeroplanes
- because pure has a low density and is too soft
16
Q
Why are alloys harder and stronger than pure metals?
A
- contain different sized atoms. Added atoms disrupt the regular lattice arrangement.
- different sized atoms DISORT the layers
- layers no longer in uniform —> cont slide over each other easily (so alloy harder and stronger)
17
Q
What are ceramics?
A
- non metal solid
- high melting points
- not made up of carbon based compounds
18
Q
How do we use wet clay to make ceramics? What is the ceramics used to make?
A
- wet clay found in the ground and moulded into various shapes
- heated in a furnace
- clay hardens at high temperatures
- into ceramics
- pottery and bricks
19
Q
What is an example of transparent ceramic? What are the two types?
A
Glass:
- soda lime glass made by heating a mixture of limestone sand and sodium carbonate
- borosilicate glass: limestone sand and sodium carbonate but also boron trioxide giving it a higher melting point
20
Q
What are composites mostly made out of? What does that make them?
A
- matrix: surrounding and binding together the fibres of the other material
- the reinforcement: fibres, fragments or particles of the material embedded within the matrix
- stronger and harder
21
Q
How can we soften polymers?
A
Adding plasticisers which reduce the MP and rigidity of the polymer chains
22
Q
How can we increase the hardness of polymers?
A
Adding cross links to soft polymers or chains between polymer chains (covalently bonded so lot of energy needed to overcome them)
23
Q
Examples of composites (what is the matrix and reinforcement)? Where are they used?
A
- fibreglass: glass fibres in polymer matrix, known for low density and high strength (vehicles and sporting equipment)
- carbon fibre composites: polymer matrix reinforced with carbon fibres or carbon atom chains. Strong and light. (Aerospace and automotive applications)
- concrete: sand and gravel (aggregate) in cement matrix. Robust so ideal for building materials
- wood: natural composite made up. Of cellulose fibres held together by organic polymer matrix (construction and furniture)
24
Q
What do the properties of polymers depend on?
A
- what monomers they’re made up from
- conditions under which they are made (e.g. temperature and pressure)
- chain structure/ density
- intermolecular forces
25
What are thermosoftening vs thermosetting polymers?
- thermosoftening: melt when heated. Can be reheated and reshaped,Ofer flexibility in manufacturing and recycling
- thermosetting: dont melt when heated, suitable for heat resistant applications (permanently hardens when heated)
26
What is low density polythene?
- polymerising ethene at moderate temperatures and pressures
- more flexible
- used for bags and water bottles
27
What is HDPE?
- polymerising ethene at higher temperatures and pressures
- more rigid
- used for water tanks and pipes
28
What is the haber process?
- industrial method for producing ammonia
- ammonia important for making nitrogen-based fertilisers
29
Why do we need to make ammonia?
- plants need nitrogen to synthesise amino acids
- amino acids used to make proteins essential for growth
- plants need it from soluble nitrate ions in the soil
- first step in manufacturing nitrate ions to supporting higher yield agriculture to feed growing population
30
Whats the reaction for the haber process?
N2 + 3H2 —> 2NH3
<—
31
What happens inside a reactor?
1) purify hydrogen (natural gas) and nitrogen (from the air) and enter the reactor
2) passed over an iron catalyst so they react and form ammonia gas as a product
3) any unreacted hydrogen and nitrogen pass into a condenser alongside the ammonia gas
4) condenser lowers the temperature of the mixture of the three gasses to a temperature where only ammonia condenses into a liquid
5) liquid ammonia collected as a product. Unreacted hydrogen and nitrogen are recycled back to the reactor —> so NOT wasted.
32
How do we purify nitrogen?
Via fractional distillation
33
How do we get hydrogen?
Derived from methane in steam reforming
34
When is yield of ammonia highest?
When there’s a low temperature and high pressure
35
What type d reaction is the Haber process?
- reversible reaction
- where the forward reaction is exothermic
36
What happens to the reaction in a reactor (haber process)? How do we increase the yield?
- dynamic equilibrium is set up when reaction occurs in reactor (forwards and backwards reaction happening at the same rate)
- equilibrium needs to shift to the left
37
Conditions for the habber process?
- Low temp causes equilibrium to shift to the right so amounts of products increases
- high pressure causes equilibrium to shift to the side with fewer molecules (the right) so amount of products increases.
38
Conditions used by industrial process?
- 450C
- 200 atm
- iron catalyst
39
What are the compromises with using a temp of 450C and 200atm pressure in the haber process? What helps with the rate of the reaction
- higher pressure increases the yield but if its too high the cost of maintains that pressure would be expensive.
- lower temp increases yield but slows rate of reaction
- iron catalyst increases the rate by providing an alternate reaction pathways with low activation energy.
40
What are the earth natural resources used for?
- warmth
- shelter
- food
- transport
41
What are the bonds in soda lime glass?
(Na2CO3), (SiO2), (CaCO3) —> covalent bonds
42
What natural resources are used to provide warmth?
- natural gas: heating homes and water
- firewood: traditional source of heat in rural ares
43
What natural resources are used for shelter?
- Sand: used to make concrete for modern construction
- Stone: making durable and weather resistant structures
-clay: used for making bricks and tiles for homes
44
What does clay contain?
- ionic metal compounds
- covalently bonded non metals
45
What natural resources do we use for food?
- soil: grow crops and support agriculture
- fish: natural source of nutrition
46
What natural resources are used for transport?
- crude oil: converted into fuels for powering vehicles
- iron ore: used to produce steel for constructing vehicles
47
How are the earths natural resources improved?
By man made natural resources such as agriculture and synthetic processing
48
How does agriculture improve products?
- food: fertilisers increase crop production, wild caught fish are supplemented by farm raised fish
- timber: managed timber plantations help provide a continuous supply of wood alongside naturally grown forests
- clothing: agriculturally produced cotton and hemp supplements wood and silk
- fuels: traditional wood logs supplemented by corn ethanol or biofuels
49
Why are ceramics Brittle?
- theres a presence of crystalline reigons
- if ions are displaced, like charges are moved next to eachother generating repulsive forces that cause materials to shatter
50
What can we used to make kayaks and small boats?
- glass fibres woven into a mat
- then embedded in polymer resin
- makes a tough waterproof material with low density
51
What can supplement or replace petroleum diesel?
Biodiesel produced from rapeseed and soybean oil crops
52
What is the composition of concrete?
Mixing cement, water and aggregates (crushed rock, sand, stones)
53
Properties of cement?
Durable, fire resistant, strong under compression
54
Limitations of concrete?
Poor tensile strength
55
What is reinforced concrete?
- adding steel rods and mesh
- overcomes low tensile strength of concrete
56
How to produce cement?
Heat limestone with clay in a kiln
57
What is the composition of reinforced concrete?
- matrix: cement
- reinforcement: aggregate
- structural reinforcement: steel
58
What are examples of synthetically improving products?
- cotton: supplementing natural fibres with synthetic fibres (e.g. polyester) in clothes
- rubber: supplementing natural rubber with synthetic rubber in tyres
- leather: synthetic layer in clothing and furniture
- wood: engineered wood such as plywood in construction
59
Where do finite resources come from?
- earth
- oceans
- atmosphere
(Metal ores, fossil fuels, minerals)
60
How does chemistry play a role in converting natural resources into useful products?
- Improving agricultural processes: helps in the development of pesticides and fertilisers which increase food production
- Creating sustainable materials: developing materials that will meet our needs whilst ensuring that the future generation can meet theirs
61
What is sustainable development?
- developmental approach that considers the long term impact on the environment
- it aims to create products that fulfill our current needs without depleting resources or harming the environment for future generations
Chemistry
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