1
Q
What is the Haber Process?
A
The process by which ammonia is manufactured, using hydrogen and nitrogen, which are extracted from methane and the air respectively.
2
Q
How does the Haber Process work?
A
Stage 1: H2 and N2 gases are pumped into the compressor through pipes
Stage 2: The gases are compressed to about 200 atmospheres inside the compressor
Stage 3: The pressurised gases are pumped into a tank containing layers of iron catalyst beds at a temperature of 450°C. Some of the hydrogen and nitrogen react to form ammonia in the following reversible reaction:
N2 (g) + 3H2 (g) ⇌ 2NH3 (g) (with iron as a catalyst)
Stage 4: Unreacted H2 and N2 and product ammonia pass into a cooling tank. The ammonia is liquefied and removed to pressurised storage vessels
Stage 5: The unreacted H2 and N2 gases are recycled back into the system
3
Q
Why are nitrogen-based fertilisers needed for plants?
A
Plants need nitrogen to grow, as it is one of the materials used to make proteins. Farmers need fertilisers to replace nitrogen in the soil, as some of it is removed when they harvest crops.
4
Q
Why is ammonia important?
A
Making fertilisers, explosives, textiles
5
Q
What is the temperature and pressure of the Haber Process?
A
temperature- 450 C
pressure - 200atm
6
Q
Why is the pressure 200 atm?
A
Increasing the pressure, causes the equilibrium to favour the forward reaction, so more ammonia is made. However, increasing the pressure too high would be very expensive, as a strong chemical plant would be needed so the pipes can cope with the high pressure.
200 atm gives a lower yield than it would with higher pressures, but it reduces the cost and helps make a reasonable rate of reaction.
7
Q
Why must there be a high yield of ammonia?
A
This is to ensure chemists make a profit, since it costs a lot of money to get methane gas for the hydrogen, and to separate the nitrogen from other gases in the air
8
Q
Why is the temperature 450 degrees C
A
Lowering the temperature would increase the amount of ammonia produced, as the forward reaction is exothermic, meaning that it increases the temperature of the surroundings, opposing the change introduced. However, decreasing the temperature too much would lead to gas molecules colliding less frequently, slowing the rate of reaction.
450 degrees is chosen to keep the reaction going at a reasonable rate, despite decreasing the yield.
9
Q
Why is an iron catalyst used?
A
to speed up both the forward and backward reactions, so more ammonia is produced.
10
Q
How does ammonia react with nitric acid?
A
It reacts in a neutralisation reaction to form ammonium nitrate.
NH3 + HNO3 → NH4NO3
11
Q
How does ammonia react with phosphoric acid?
A
It reacts in a neutralisation reaction to form ammonium phosphate.
3NH3 + H3PO4 → (NH4)3PO4
12
Q
How does ammonia react with sulfuric acid?
A
It reacts in a neutralisation reaction to form ammonium sulfate.
2NH3 + H2SO4 → (NH4)2SO4
13
Q
How can you collect pure, dry crystals of ammonium sulfate from its solution?
A
- Put 25cm3 of ammonium solution in a conical flask
- Add 1cm3 of dilute sulfuric acid at a time, swirling the flask.
- Dip a glass rod into the solution, and test a drop of this on blue litmus paper
- Keep adding acid until the litmus paper turns pink
- Repeat titration until you get concordant results
- Pour solution into evaporating dish
- Heat this on a water bath until solution has halved
- Leave rest of solution to evaporate off, leaving behind crystals of ammonium sulfate
- Dry with clean piece of filter paper
14
Q
What are NPK fertilisers?
A
As will as nitrogen (N), crops also require phosphorous and potassium (P and K). Farmers buy fertilisers that have formulations of compounds of potassium, nitrogen and phosphorous to improve their crop yield.
15
Q
Where does the nitrogen come from for NPK fertilisers?
A
It comes from ammonia, made in the Haber process, which is reacted with acids to make fertilisers like ammonium nitrate and ammonium sulfate.
16
Q
Where does the phosphorous come from for NPK fertilisers?
A
It comes from deposits of phosphate containing rock, which is dug or mined from the ground. This cannot be used directly on soil, as it is insoluble in water.
17
Q
How is phosphate rock treated with acids so it can be used as a fertiliser?
A
- with nitric acid to produce phosphoric acid H3PO4 and calcium nitrate, Ca(No3)2. The phosphoric acid reacts with ammonia to make ammonium phosphate.
- with sulfuric acid to produce single superphosphate, a mixture of calcium phosphate, Ca3(Po4)2 and calcium sulfate, CaSO4
- with phosphoric acid to make triple superphosphate, which is calcium phosphate, Ca3(Po4)2
18
Q
Where does the potassium come from for NPK fertilisers?
A
It is mined from the ground in the salts, potassium chloride KCL, and potassium sulfate, K2SO4. All potassium compounds are soluble in water, so they can be separated from impurities and used directly.
19
Q
What are the Earth’s natural resources used for?
A
Make homes to live in
Provide food
Fuel transport
Energy to cook and stay warm
They can be living (plants and animals), or non-living things (fossil fuels, food, water).
20
Q
What is a resource?
A
a natural material from the Earth, oceans, or atmosphere
21
Q
What are some examples of synthetic materials chemists have made to replace finite resources?
A
Wool = Clothes,carpets = Acrylic fibre (poly(propene))
Cotton= Clothes, textiles = polyester
silk = clothes = nylon
rubber = Tyres, washers = Various synthetic polymers, like poly(butadiene)
wood = construction = PVC, composites (e.g MDF)
22
Q
What is sustainable development?
A
processes that enable the need of the current generation to be met without compromising the availability of natural resources for future generations
23
Q
What has the application of scientific advancement allowed?
A
The application of scientific advancement has allowed us to maximise the production of natural products. An example of this is fertilisers to increase crop yield.
24
Q
What are finite resources?
A
Finite resources are resources that are being used up at a faster rate than they can be replaced. If we continue to use these resources at their current rates, they will eventually run out.
25
What are some examples of finite resources?
Fossil fuels
Metal ores
Minerals from the Earth’s crust
Limestone
26
What are finite resources often used for?
Finite resources are often processed to make the desired products, or they are used as the raw materials to make the new products.
27
Why is the extraction of finite resources bad?
These processes require energy, and make the extraction process less sustainable. The extraction of non-renewable resources carries risks, as the Earth’s natural resources are being depleted and large amounts of energy are being consumed in the process of extraction.
28
What is a renewable resource?
Renewable resources are those that can be replaced at the same rate that they are used up.
29
What are some examples of renewable resources?
Timber
Crops for biofuels
Ethene produced via fermentation
30
How is ethene finite and renewable?
An example of a renewable resource is ethene, produced via fermentation of sugar cane/beet (a renewable resource). However, ethene can also be made from crude oil, which is a finite resource. Using a renewable resource as the raw material for the production of ethene makes plastics like poly(ethene) more sustainable than those made from crude oil.
31
Why can we only decide how long finite resources will last for by estimates?
There is uncertainty about amount of ‘usable’ fossil fuels left on earth
Rate of future consumption
Possibility of discovering new deposits
New technologies created to burn remaining fossil fuels more
32
What is potable water?
Potable water is water that has been processed and is safe for human consumption and daily use
33
What is the difference between pure water and potable water?
- pure water is solely made up of H2O molecules, whereas potable water contains different substances like dissolved minerals and salts, or microbes
34
What are the characteristics of potable water?
Have a pH between 6.5 and 8.5.
The dissolved substances (e.g. salts) will be present is very small regulated quantities
Be free of bacteria or potentially harmful microbes
35
When is water considered fresh, and how is surfacewater and groundwater collected?
- water is fresh when it is relatively free from dissolved substances/microbes (e.g rainwater)
- water can collect in reservoirs, lakes and rivers, known as surface water
- can collect in aquifiers, porous rocks that store water underground = groundwater
36
What does the origin of freshwater depend on?
- the climate
- warmer areas = water dries up before it can be collected = so it is taken from underground
37
What are the two main steps in the process to ensure fresh water is safe and suitable for use?
1. Filtration
2. Sedimentation
3. Sterilisation
38
What happens during filtration?
Debris such as pieces of soil and dirt, small pebbles, twigs, etc. are removed by a wire mesh screen
After this, other debris is filtered through sand beds and gravel
39
What happens during sedimentation?
Chemicals like aluminium sulfate or iron sulfate are added to the water to make fine particles clump together (flocculation) and sink to the bottom as sludge, which is then removed.
40
What happens during sterilisation?
Ultraviolet light or ozone can be used to sterilise water or alternatively chlorine gas is bubbled through the water
This removes any dangerous bacteria or microbes
41
When is desalination used?
- when aquifiers are not present
- collection of surface water is limited
42
How does desalination work?
- it involves the treatment of seawater to remove the salt by distillation of reverse osmosis = involves the use of membranes
- salt water is put through a semi-permeable membrane, and only water molecules can pass through as the membrane stops large molecules and ions from passing though it
43
Disadvantages of desalination?
- expensive
- consumes large amounts of energy
- not ideal when producing large quantities of fresh water
- used in regions with a very hot climate such as Saudi Arabia
44
Why does domestic and agricultural sewage need to be processed?
- Both domestic and agricultural sewage needs to be processed to remove organic matter, harmful microbes, particulates and toxins
- This can then be safely returned to freshwater sources i.e. lakes and rivers
- If this process did not take place, it could potentially pose health risks for the population
45
What are some causes of domestic waste water and agricultural waste water?
- domestic = washing up dished, showers, baths and cooking
- agricultural = waste from animal farms, nutrient runoff
46
Why does industrial waste need to be processed?
Waste water that is produced by the Haber process and other industrial processes needs to be gathered and treated appropriately
Harmful chemicals and organic matter are present in industrial waste
This therefore means that additional treatment has to be in place to ensure it is safe for the environment
47
What are the steps at a sewage treatment plant?
1. Screening and grit removal
2. Sedimentation
3. Aerobic digestion
4. Anaerobic digestion
48
What happens during screening and grit removal?
The first stage of treatment removes large materials such as plastic bags and twigs and grit by screening
49
What happens during sedimentation?
Sedimentation comes next which occurs in a settlement tank. The water is allowed to stand still in the tank while heavier solids sink to the bottom creating sewage sludge, whilst lighter matter which is also known as effluent, floats to the top
50
What happens during aerobic digestion?
The effluent is removed and treated by biological aerobic digestion
This involves pumping air into the water to encourage the breakdown of organic matter and other microbes by aerobic bacteria
51
What happens during anaerobic digestion?
Anaerobic digestion is then used to break down the sewage sludge from the bottom of the settlement tank. It is firstly removed and placed in large tanks where bacteria break it down
Anaerobic digestion releases methane gas as a by product from the organic matter in the sludge. Methane gas is used as a source of energy and the leftover, digested waste as a fertiliser
52
How can you remove toxic substances withing wastewater?
When there are toxic substances within waste water, it is important to use additional phases of treatment
This can include using membranes, adding additional chemicals e.g. to precipitate metals out of solution, and also U.V. radiation
53
What are the disadvantages of treating wastewater?
Sewage water is often treated in areas where there is little freshwater available
Though this process is longer than processing and preparing freshwater, it uses less energy than the desalination of salt water
54
Required Practical 8: Purifiying the water?
1 Half fill a beaker with tap water and add some crushed ice to make an ice bath.
2 Put a boiling tube into the ice bath.
3 Add 100 cm3 of solution and a few anti-bumping granules (or broken pottery) into a 250 cm3 Pyrex conical flask.
4 Push a thermometer and an ‘n’ shape delivery tube through two holes in a bung.
5 Put the bung into the conical flask.
6 Adjust the height of the thermometer so that the bulb is in line with the delivery tube.
7 Put the conical flask on top of a tripod and gauze.
8 Put the end of the delivery tube into the test tube in the ice bath.
9 Ignite the Bunsen burner, with the air hole closed onto the safety flame.
10 Open the air hole of the Bunsen burner so the flame turns blue and move the Bunsen burner under the tripod to heat the solution.
11 Note the temperature on the thermometer when it is a constant value. This is the boiling point of the distillate.
12 Once half a boiling tube of distillate has been collected, remove the delivery tube and then turn off the Bunsen burner. Use a pH probe to test the pH of the distillate
55
Required Practical 8: Analysing the sample?
1. Use universal indicator to test the pH of the water.
2. Measure and record the mass of an empty evaporating basin.
3. Pour 10 cm3
water into the evaporating basin and evaporate the water using a
bunsen burner until the most of the water has evaporated.
4. Once the evaporating basin is cool, reweigh and record the change in mass.
5. Calculate the mass of dissolved solids in the water
56
Why is copper useful?
Copper is an excellent conductor of heat and electricity and does not corrode quickly. These properties make it a good material for wiring and plumbing.
57
How is copper found and how is it made pure?
Copper is not very reactive and can occur native but it is rare to find pure copper. Usually, it is found combined with other elements, such as in the ore malachite.
The copper must first be extracted from its compounds. Electrolysis is then used to remove impurities from this copper.
58
How can we produce copper?
1. Reduction with carbon = carbon is more reactive so it can reduce the metal oxide leaving the element
2. Smelting
3. Extracting by displacement = a more reactive metal than copper can be used to displace it from its ore
59
How does smelting work?
- heat the carbon up to a high temperature so that the impurities react with the oxygen in the air
- copper sulphide + oxygen → copper + sulphur dioxide
60
What are the problems with the curent methods used to extract low-grade ores?
- they cause significant environmental damage, as traditional mining involves a great deal of digging, moving and disposing of large amounts of rock
- contribute greenhouse gases to the atmosphere
- deplete stores of metal ores, which are finite = so they become more and more scarce
61
What will form at the electrodes when electrolysis is carried out on copper sulphate solution?
Cathode
Cu2+ (aq) + 2e- = Cu (s)
Anode
4 OH- (aq) = 2H2O (l) + O2 (g) + 4e-
62
How do we purify copper?
- electrolysis
- The anode (positive electrode) is made of the impure copper which is to be purified.
- The cathode (negative electrode) is a bar of pure copper.
- The two electrodes are placed in a solution of copper(II) sulfate.
- Copper ions leave the anode and are attracted to the cathode, where they are deposited as copper atoms.
- The pure copper cathode increases greatly in size, while the anode dwindles away.
The impurities left behind at the anode form a sludge beneath it.
- cathode = Cu2+ (aq) + 2e- -> Cu (s)
- anode = Cu (s) -> Cu2+ (aq) + 2e-
63
What are two new methods for extracting metals and what are their advantages and disadvantages?
- phytoextraction
- bioleaching
Both of these methods avoid the significant environmental damage caused by the more traditional methods of mining
Biological methods are, however, very slow and also require either displacement or electrolysis to purify the extracted metal
Both techniques are also used to extract metals from mining wastes, which may contain small quantities of metals or toxic metals that need to be removed from that environment
64
What is phytomining and how does it work?
This process takes advantage of how some plants absorb metals through their roots
The plants are grown in areas known to contain metals of interest in the soil
As the plants grow the metals are taken up through the plants vascular system and become concentrated in specific parts such as their shoots and leaves
These parts of the plant are harvested, dried and burned
The resulting ash contains metal compounds from which the useful metals can be extracted by displacement reactions or electrolysis
65
What does reduce, reuse and recycle entail?
Conserve limited natural resources
Reduce energy consumption
Reduce waste production
Limit environmental impact
66
Why do we need to reduce resource use?
Much of the energy for the processes comes from limited resources
67
What are the environmental venefits of reducing resource use?
Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts.
Noise
Dust
Visual pollution
Water mixing with the metal ores in the ground can cause acidic water which pollutes water sources
Destroys habitats
68
Why should we reuse resources and give two examples of them?
Glass bottles and plastic carrier bags
There is less demand for new products
69
How can we encourage people to reuse resources?
Reduce demand for them
Bringing carrier bags to the supermarket so the supermarket has to produce fewer bags
The government can (and has already) introduced a charge to encourage people to bring their own bags.
In the first year, plastic bag use was reduced by 83%
70
What do you have to do when recycling?
When recycling you have to separate materials.
The amount of separation required depends on the material and the properties that you want the final product to have
71
How can glass bottles be recycled?
Glass bottles can be recycled by crushing and melting them before making new glass products.
72
How can metals be recycled?
Metals can be recycled by melting and recasting/reforming into different products
73
Can glass just be reused?
Glass bottles only need to be washed and sterilised before they can be reused
74
How is iron recycled?
Iron is extracted from its ore at a blast furnace.
Steel is a man-made iron alloy that is used for many things.
We can recycle scrap steel by adding it to the iron from a blast furnace. This helps reduce the amount of iron that we extract from our limited resources of iron ore.
75
How is aluminium recycled?
First the aluminium cans are squashed and shredded into small pieces. The pieces move on a conveyor belt under a powerful magnet to remove any iron present. Then the pieces are blasted with hot air to remove any labels or ink on the outside of the can. The pieces are then fed into a furnace at 700 °C where the impurities, called dross, rise to the surface and are scraped off. The pure aluminium is then cooled and cast into ingots, which then go to the rolling mill where they are made into thin sheets for making cans.
76
Economic advantages of recycling?
Itis economically benefcial to recycle metals, especially those that are costly to extract such as aluminium
Recycling is fast becoming a majorindustry and provides employment which feeds
back into the economy
77
Environmental advantages of recycling?
Mining and extracting metalfrom ores has detrimental effects on the environment and
ecosystems
Itis much more energy efficient to recycle metals than itis to extractthem
as melting and re-moulding requires less energy
Recycling decreases the amount of waste produced, hence saving space at landfill sites
and energy in transport
78
Advantages of recycling for raw materials?
There is a limited supply of every material on Earth
As global populations increase there is a greater need for effective recycling methods to attain sustainable development
Mining and extraction use up valuable fossil fuels, which contributes to climate change
79
Disadvantages of recycling?
Collection and transport of material to be recycled requires energy and fuel
Workers, vehicles and work sites need to be organised and maintained
Materials need to be sorted before they can be recycled which also requires energy and labour
Products made from recycled materials may not always be of the same quality as the original
80
What happens to glass that is broken or damaged?
Glass that is broken or damaged and cannot be reused is separated
by colour and composition before being recycled
81
What is corrosion?
destruction of materials by chemical reactions with substances in the environment which act on them over a period of time
most metals can corrode in the prescence of oxygen to form the corresponding metal oxide
82
What is rusting?
this is the name given for the corrosion of iron in the presence of water and oxygen from the air
83
Equation for rusting?
iron + water + oxygen = hydrated iron oxide (III)
84
What is rust?
a soft solid substance that flakes of the surface of iron easily, exposing fresh iron below, which then undergoes rusting
over time all of the iron rusts and its structure becomes weakened
85
How can you investigate rusting?
- setting up a series of control test tubes containing nails, one with air and water, one with boiled water and oil, one with anhydrous calcium chloride and air
- the test tube with air and water will rust as it is in contact with both oxygen and water
- the test tube with boiled water and oil will not rust because it is not in contact with oxygen as the oil provides a barrier for oxygen to diffuse into the boiled water, and the boiled water removes any dissolved oxygen
- the nail with anhydrous calcium chloride and air will not rust, because calcium chloride is a drying agent, which will absorb water molecules present due to oxygen, and there is no actual water in the tube
- this experiment shows that both air and water must be present for rusting to occur
86
How can we prevent rusting ?
- plastic coating
- oiling
- galvanising
- painting
87
Why should we prevent rusting?
it is expensive and wasteful
88
How can we prevent rusting using a barrier method?
- coating iron with barriers will prevent rust because it will stop the iron from coming into contact with water and oxygen
- however, if coatings are washed away or scratched, iron exposed to water and oxygen and will rust
- common barrier methods include paint, oil, grease and electropainting
89
Why does iron keep rusting?
- once iron begins to rust, it will continue to corrode internally as iron is porous, allowing both air and water to come into contact with fresh metal that is under any barrier surfaces that have been broken or scratched
90
What is sacrificial protection?
- iron can be prevented from rusting through the reactivity series
- more reactive metal can be attached to a less reactive metal
- The more reactive metal will oxidise and therefore corrode first, protecting the less reactive metal from corrosion
91
Example of sacrificial protection?
- zinc bars on the side of ships
- Zinc is more reactive than iron therefore will lose its electrons more easily than iron and is oxidised more easily
- For continued protection,the zinc bars have to be replaced before they completely
corrode
92
What is galvanising?
- iron to be protected is coated with a layer of zinc
- This can be done by electroplating or dipping itinto molten zinc
- ZnCO is formed when zinc reacts with oxygen and carbon dioxide in the air and protects
the iron by the barrier method
- If the coating is damaged or scratched,the iron is still protected from rusting
by sacrificial protection
93
How is aluminium protected from corrosion?
- Aluminium has an oxide coating that protects the metal from further corrosion
- The oxide layer acts as a barrier
94
What is an alloy?
mixture oftwo or more metals or metal with a non-metal such as carbon
95
What are some properties of alloys?
- stronger and harder than the original metals
- resistance to corrosion or extreme temperatures
- these make alloys more useful than regular metals
96
Why are alloys harder than pure metals?
- Alloys contain atoms of different sizes
- This distorts the regular arrangements of atoms
- So it is more difficult for the layers of atoms to slide over each othe
97
Copper alloys?
- bronze is made from copper and tin
- it is harder than copper and is used to make ornaments and metals
- brass is made from copper and zinc
- Itis decorative and corrosion resistant and is used for low friction ornamental
purposes such as plumbing and carpentry fitting
98
Gold alloys?
- Gold alloys are usually made with silver copper and zinc
- They are used to make jewellery
- Carats are used to express the purity of gold jewellery. It refers to how many parts out of 24 are pure gold.
- Pure gold with nothing else added is said to be 24 carat
- A 12 carat piece of gold jewellery therefore contains 50% gold
- For example a 12 carat necklace that weighs 50g contains 50% gold, so 25 grams
99
Steel alloys?
- Steels are alloys ofiron that contain specific amounts of carbon and other metals
- High carbon steel is strong but brittle
- Low carbon steel is softer and more easily shaped
- Stainless steels (steel containing chromium and nickel) are hard and resistant to
corrosion
100
Aluminium alloys?
Aluminium is mixed with copper, manganese and silicon for aircraft body production as
aluminium alloys tend to be stronger and lighter than pure aluminium
As well as being lighter and stronger, itis also more corrosion resistant than aluminium
101
What are some uses of alloys?
high carbon steel = cutting materials
low carbon steel = building frames, cookware, car bodies
stainless steel (iron, chromium and nickel) = Cookware, cutlery, car bodies
bronze = ornaments and medals
brass = plumping and carpentry
magnalium (aluminium and magnesium) = Aircraft construction and production of fireworks
(more stable than pure magnesium but still burns
brightly)
102
What is a life cycle asssesment?
A life cycle assessment(LCA) is an analysis of the overall environmental impact that a product may have throughout its lifetime.
103
What are the four main stages of a life cycle assessment?
Extracting and processing the raw materials
needed
Manufacturing the product and its packaging
Using the product during its lifetime
Disposing of the product at the end of its useful
life
104
What are raw materials and what are their environmental impact?
Obtaining the necessary raw materials has an impact on the environment which may
include:
- Using up limited resources such as ores and crude oil
- Damaging habitats through deforestation or mining
105
What is manufacturing and what is its environmental impact?
This is creating the product and packaging.
Its environmental impact includes:
- Using up land for factories
- The use of fossilfuelled machines for production and transport
- Production of waste
106
What is a product's use and what is its environmental impact?
The impact of a product on the environment during its use
It depends on the product type.
For example, a wooden desk has very little impact whereas a car will have a significant impact(air pollution).
Planes will have a significant environmental impact due to the carbon emmissions they release and their aluminium bodies.
Single use plastic is also bad.
107
What is disposal and how does it have an environmental impact?
This is the disposal at the end of its useful life. It has several environmental impacts:
Using up space at landfill sites
Whether the product or its parts can be recycled or reused
108
ESQ: Discuss the use of energy during the lifetime of a pillowcase. Describe one way in which the energy use could be significantly reduced. [3-marks]
One quarter of the energy use is associated with making the pillowcase,
and very little in disposing of it.
The greatest use of energy happens when it is being used, probably
because of washing, drying and ironing the pillowcase.
Energy use could be reduced by drying it outside and without ironing it, and washing it at a lower temperature.
109
What is a comparitive LCA?
Comparative LCAs can be used to evaluate which of two alternative products will have a lower negative impact on the environment.
110
How is a lifecycle assessment carried out?
- using the data of the given product and the criteria of the asssessment
- some stages are easily quantifiable, e.g the amount of water used during manufacturing
- However, other stages are more difficult to allocate a numerical value to, e.g. the polluting effect of a product
- In these cases, people can make a value judgement abouttheir effect but this is not an objective process and different people may allocate different values, or they may be biased
- Rarely is there a perfect product with zero environmental impact, so often a compromise is made between environmental impact and economical factors
111
Example conclusion for an LCA?
Considering both life-cycle assessments,the plastic bag may be the better option. Even though they aren’t biodegradable,they do have a much longer lifespan and thus
are less harmful than paper bags. Much depends on the use of the item, Ifthe paper bag is recycled then it could be more favourable to use it
If the plastic bag is used only once,then then the argument for using plastic bags is less favourable
112
What are some things to consider when doing an LCA?
Different aspects of a products LCAs may be subjective or objective.
Objective- not influenced by personal feelings or opinions in considering and representing facts
Subjective- based on or
influenced by personal
feelings, tastes, or opinions.
113
What are some limitations of LCAs?
Some might have bias
Not completely objective
Depends on who makes the LCA - eg the
company making the product
114
Life cycle assessment for paper and plastic shopping bags?
Raw materials:
Plastic = Crude oil is a finite source which requires a lot of energy to process
Paper = Recycled paper or tress. Making
paper requires more energy than recycling paper but much less than
making plastics
Manufacturing:
Plastic = Fractional distillation cracking &
polymerisation, not much waste as crude oil is completely used and
cheap to manufacture
Paper = Pulping paper uses a lot of energy,
sulfur dioxide and produces waste
Usage:
Plastic = Reusable
Paper = Most are not reusable
Disposal:
Plastic = can be recycled but is costly and
produces pollution. Can be stored in landfill,takes up space and is not
biodegradable
Paper = Biodegradable, non-toxic and can be recycled
115
Evaluate these materials for making food plates. You should use features of Life Cycle Assessments. [4-marks]
Raw materials:
- trees are renewable
- curde oil and clay is finite
Manufacturing:
- paper plates use least packaging = conserve raw materials = need less transportation overall as more plates in a box
Use and operation:
- paper plates are single use = replaced often
- ceramic plates last longer than polymer plates = replaced the least often
Disposal:
- polymer plates take up landfill which is running out
- paper plates can be used to make new products
- recycling conserves raw materials
Judgment:
- ceramic plates are the best because they last for so long
116
What are ceramics?
non-metal solids with high melting points
widely used in construction materials and domestic appliances
117
What are some properties of glass?
- transparent
- strong
- insulates against heat
- durable
118
What are two types of glass?
1. Soda-lime glass (most commonly used)
2. Borosilicate gate
119
What is soda lime glass made from?
- silicon dioxide (sand)
- calcium carbonate (limestone)
- sodium carbonate (soda)
120
What is borosilicate glass made from?
- silicon dioxide (glass)
- boron trioxide
121
How is borosilicate glass different from soda lime glass?
- melts at a higher temperature than soda lime glass
- used for ovenware and test tubes
122
How is glass made?
Raw materials heated to 1500 C to form a liquid
Cooled so that it sets as a solid with an irregular
structure
Other materials can be added to produce different colours or properties
123
How are clay ceramics made?
- clay is a soft material dug up from the earth
- when it is soft and wet, clay soil can be moulded into different shapes
- when it is fired in a furnace, it hardens to form a clay ceramic
124
What are some examples of ceramics?
- pottery
- bricks
125
Properties of ceramics?
- hard
- wear-resistant
- brittle
- heat resistant (refractory)
- thermal and electrical insulators
- can be used as bricks which can withstand high
pressures and weights
126
What is the structure of ceramics?
Compounds of metals and non-metals
Ionic and covalent bonding
Giant structures
Form layers
When wet, water gets between layers
allowing for the shape to be molded
On heating the water is driven out
127
How are composites made?
- a matrix surrounding or binding together
- …fibers or fragments of another material (the reinforcement)
128
What are some examples of composites?
- fibreglass (glass fibres + polymer resin)
- concrete (steel + concrete)
- carbon fibre reinforced polymer (carbon fibres + polymer resin)
- wood = natural composite (long cellulose fibres + lignin)
129
What do the properties of composites depend on?
The properties of composites depend on the reinforcement and matrix used so composites can be tailor engineered to meet specific needs
130
What can composites be designed to offer?
low weight
stiffness and strength
low coefficient of expansion
resistance against fatigue
ease in manufacturing complex shapes
simple repair of damaged structures
resistance to corrosion
131
How has steel reinforced concrete been adapted?
- has immense tensile and compressive strength
- can be used as columns and supporting structures in construction
132
What do the properties of monomers depend on?
- The monomers they are made from
- The conditions they are made in
133
What can ethene be polymerised into?
- high density (HD) polyethene
- low density (LD) polyethene
134
Low density poly(ethene)?
- made at high temperature and moderate pressure
- used for bags and bottles, where flexibility is required
135
High density poly(ethene)?
- produced at lower temperatures and pressures and with the use of a catalyst
- has a rigid structure and is used to produce water tanks, mouldings and drain pipes
136
How can we divide polymers?
- thermosoftening
- thermosetting
137
Thermosetting polymers?
- consists of monomer chains
- fixed together with strong covalent bonds = cross linking
- strong and rigid and does not melt when they are heated
- this is because lots of energy would be required to overcome the cross links
- used in electrical plugs
138
Thermosoftening polymers?
- individual, tangled chains entiwined with each other
- no cross links
- low melting points as there are weak intermolecular forces between chains
- melted when heated, and can be melted and remoulded to form different shapes
- used to make packaging and plastic bottles
139
What is bioleaching?
Certain bacteria can break down low grade ores to produce an acidic solution containing metal ions, called a leachate.
It can be used to extract copper metal, not needing high temperatures, but it produces toxic chemicals that can damage the environment.
Chemistry
flashcards
Decks in class (12)
# Cards
-
4.1-Atomic Structure and the periodic table91
-
4.2- Bonding, Structure and the different properties of matter94
-
4.3- Quantitative Chemistry28
-
4.4- Chemical Changes78
-
4.5- Energy Changes42
-
4.6- The rate and extent of chemical exchange30
-
4.7- Organic Chemistry46
-
4.7-Organic Chemistry 249
-
4.8- Chemical Analysis79
-
4.9- Chemistry of our atmosphere27
-
4.10- Using resources139
-
mock questions answered wrong10
