C6 Flashcards
1
Q
What is a metal ore?
A
A rock which contains enough metal to make it economically worthwhile to extract the metal from it.
2
Q
What is metal ore often in the form of?
A
It is often a metal oxide.
3
Q
What are the two ways of extracting metal from ore chemically?
A
By reduction with carbon or by electrolysis.
4
Q
What other ways are there of extracting metal from ore?
A
Displacement reactions and biological methods.
5
Q
What is metal extraction by reduction?
A
It can be extracted through reduction with carbon, meaning that its oxygen is removed from the ore.
6
Q
When can metal be extracted by reduction?
A
If it is below carbon on the reactivity series.
7
Q
What are the metals that are higher than carbon on the reactivity series extracted by?
A
Electrolysis, which is expensive.
8
Q
Where is the metal deposited during electrolysis?
A
At the cathode
9
Q
Why is copper purified when extracted by carbon?
A
The copper produced by reduction with carbon is impure, which doesn’t conduct well which is important as copper is used to make electrical wiring. So it is purified through electrolysis.
10
Q
How is carbon purified through electrolysis?
A
The anode is made of non-inert copper so that it dissolves in the electrolyte and forms at the cathode.
11
Q
Why are scientists looking for ways of extracting metal from low grade ores?
A
Because the supply of metal rich ores is limited but the demand for metal is growing which may lead to shortages.
12
Q
What are the biological methods used for extracting metals?
A
Bioleaching and Phytoextraction
13
Q
What is Bioleaching?
A
This uses bacteria to separate metals from their ores. The bacteria get energy from the bonds between the atoms in the ore, separating out the metal from the ore in the process.
14
Q
What is produced by Bioleaching?
A
Leachate, which contains metal ions and can be extracted by displacement or electrolysis.
15
Q
What is Phytoextraction?
A
This involves growing plants in soil that contains metal compounds. The plants can’t use/get rid of the metals and so they build up in the leaves. The plants can be harvested, dried and burned in a furnace.
16
Q
What are the advantages/disadvantages of Bioleaching and Phytoextraction?
A
They are safer for the environment than non-biological methods but they are very slow.
17
Q
What is an alloy?
A
A mixture of two or more different metals, or a mixture of a metal and non-metal.
18
Q
Why are alloys used?
A
They have properties that are different from the metals that they are made from which are more useful.
19
Q
What is steel an alloy of?
A
Iron and carbon
20
Q
What are the properties of steel?
A
It’s harder and stronger than iron. Iron is much more likely to rust (corrode) than steel. Its used to make things like bridges, engine parts, washing machines etc.
21
Q
What is brass an alloy of?
A
Copper and zinc
22
Q
What are the properties of brass?
A
A mixture of properties from copper and zinc, although brass is harder than either of them. Its used to make things like musical instruments and screws.
23
Q
What is bronze an alloy of?
A
Copper and tin
24
Q
What are the properties of bronze?
A
It’s much harder and stronger than copper or tin, and it’s more resistant to corrosion. Its used to make things like springs and motor bearings.
25
What is solder an alloy of?
Lead and tin
26
What are the properties of solder?
It doesn't have a definite melting point but gradually solidifies as it cools, making it useful for joining metal things together.
27
What is duralumin an alloy of?
Aluminium, with small amounts of copper, magnesium and manganese
28
What are the properties of duralumin?
It's a very low density alloy that is much stronger than aluminium. As a result its useful for making things like parts of aeroplanes.
29
What is corrosion?
A process where something is slowly damaged or destroyed by a chemical process.
30
When does iron rust?
It rusts when it comes into contact with air and water. Rust is a form of hydrated iron(III) oxide.
31
What is the equation that shows the formation of rust?
Iron + Oxygen + Water → Hydrated iron (III) oxide
32
Why is the rusting of iron a redox reaction?
Iron lose electrons when it reacts with oxygen. Each Fe atom loses 3 electron atoms to become Fe³⁺. Simultaneously, oxygen gains electrons - each O atom gains two electrons to become O²⁻.
33
How can you prevent corrosion?
You can prevent corrosion by coating the metal with a barrier. This keeps out the water, oxygen or both.
34
What methods are there to prevent corrosion?
Paint, oil, grease.
35
How does a coat of tin prevent steel from corroding?
The tin acts as a barrier, stopping water and oxygen reaching the surface of the metal. This only works when the coat of tin remains intact.
36
What is the "sacrificial" method of preventing corrosion?
You place a more reactive metal with whatever you don't want to corrode, and the water and oxygen react with this instead of the desired metal.
37
What is galvanising?
Where a coat of zinc is put onto an iron object to prevent rusting. It's more reactive than iron so it's lose electrons (and corrode) in preference to iron.
38
What does the Haber process do?
It produces ammonia (NH₃) which is used to make fertilisers.
39
What is the equation of the Haber process?
N₂ + 3H₂ ⇌ 2NH₃ (+ heat)
40
How is nitrogen and hydrogen obtained for the Haber process?
Nitrogen is easily obtained from the air which is 78% nitrogen. Hydrogen can be obtained from hydrocarbons from sources such as natural gas or crude oil.
41
At what pressure and temperature is ammonia produced at?
200 atm and 450 degrees celsius
42
Why do higher pressures favour the forward reaction (production of ammonia) in the Haber process?
There are four moles of gas on the left hand side and so the equilibrium will move to the left hand side, therefore producing more ammonia.
43
Why do lower temperatures favour the production of ammonia in the Haber process?
The forward reaction is exothermic, and so higher temperatures would mean that less ammonia is produced. Therefore reducing the temperature increases the yield of ammonia.
44
Why is the Haber process performed at only 200 atm and 450 degrees celsius when lower temperatures/higher pressures would have a higher yield?
Lower temperatures mean a lower rate of reaction - 450 degrees celsius is a compromise between maximum yield and rate of reaction.
45
What type of catalyst is used in the Haber process and why?
Iron - it makes the reaction quicker and makes it reach the equilibrium proportions quicker. It's important as, without it, temperatures would have to be higher which would decrease yield even more.
46
What are fertilisers made up of?
The three main essential elements in fertilisers are nitrogen, phosphorus and potassium.
47
Why are fertilisers used?
They replace the missing elements if they aren't present in the soil, or provide more fo them. This increases yield and the crops grow bigger/faster.
48
How is ammonia changed into fertilisers?
It's a base and can be neutralised by acids to make fertilisers (ammonium salts)
49
What different ammonia-based fertilisers are there?
Ammonium phosphate
50
Why is ammonium nitrate such a good fertiliser?
It's an especially good fertiliser because it has a high percentage of nitrogen, the ammonia and the nitric acid.
51
How do you make ammonium nitrate?
It's produced by neutralising nitric acid with ammonia.
52
How do you make ammonium sulfate?
By neutralising sulfuric acid with ammonia.
53
How do you make ammonium phosphate?
By neutralising phosphoric acid with ammonia.
54
How can you make most fertilisers?
Titration
55
What is the Contact Process used for?
To make sulfuric acid
56
What is the first stage of the Contact Process?
S + O₂ → SO₂
57
What is the second stage of the Contact Process?
2SO₂ + O₂ ⇌ 2SO₃
58
What is the third stage of the Contact Process?
SO₃ + H₂O → H₂SO₄
59
Is the oxidation of sulfur dioxide exothermic or endothermic?
Exothermic
60
How is temperature set in the Contact Process?
Although having a low temperature would increase the yield because it's an exothermic reaction, this would slow down the rate of reaction and so they compromise at 450 degrees celsius.
61
How is pressure set in the Contact Process?
There is 2 moles of gas of products and 3 moles of gas of reactants. To increase yield, you'd increase the pressure but that would be very expensive. As a result, it's usually carried at atmospheric pressure.
62
What catalyst is used in the Contact Process?
Vanadium pentoxide. This doesn't affect the equilibrium position.
63
What are the 5 things that need to be considered in industrial processes?
```
Cost of raw materials
Availability of raw materials
Energy costs
Rate
Equilibrium position
```
64
How does the cost of raw materials affect industrial processes?
Raw materials often have to be refined or purified, or produced with another reaction. This affects whether the process is economically viable and may make it unprofitable.
65
How does the availability of raw materials affect industrial processes?
Some raw materials, like crude oil, are non-renewable, so they aren't sustainable. It's best to get materials that are renewable or common.
66
How does the energy cost affect industrial processes?
Generally, higher temperatures and pressures cost more to maintain, so low temperatures/pressures are used wherever possible.
67
How does the rate of reaction industrial processes?
Sometimes yield is compromised to have a reasonable rate.
68
How does equilibrium position affect industrial processes?
Being able to control the position of equilibrium to maximise yield is important in making processes profitable.
69
What is a life-cycle assessment?
It looks at each stage of the life of a product and works out the potential environmental impact of each stage.
70
Describe the "Choice of material" life-cycle assessment
Metals have to be mined and extracted, which requires lots of energy and cause pollution. Raw materials for chemical manufacture come from crude oil which is unsustainable.
71
Describe the "Manufacture" life-cycle assessment
Manufacturing requires lots of energy and resources. It also causes lots of pollution. You need to think about waste products and how to dispose them - some can be recycled into other useful chemicals.
72
Describe the "Product use" life-cycle assessment
Fertilisers can leach into streams/rivers and damage ecosystems
73
Describe the "Disposal" life-cycle assessment
Products might be incinerated which causes air pollution.
74
Where does lots of the energy come from when extracting raw materials?
Burning fossil fuels.
75
What is the issue with using fossil fuels?
They're running out and are unsustainable. They also contribute to acid rain and climate change.
76
Why is recycling so good?
Recycling often uses a small fraction of energy needed to extract and refine the material from scratch.
There's a finite amount of resources on earth, so recycling conserves them.
Recycling cuts down on landfill.
77
How much is saved for every 1 kilogram of aluminium cans recycled?
Roughly 95% of the energy needed to mine and extract aluminium
4 kg of aluminium ore
Lots of waste
78
What are issues with recycling?
Not completely energy free - might not even be worth it.
Items need sorting to separate materials.
You can only recycle something a finite number of times.
79
What are ceramics?
Ceramics are made by baking substances, such as clay, to produce a brittle, stiff material. Examples include glass, porcelain and bone china.
80
What is clay?
A mineral formed from weathered and decomposed rock. It's soft when dug up, which makes it to easy to mould into different shapes.
It can be hardened at high temperatures. This makes it an ideal building material.
81
What are the properties of glass?
Glass is generally transparent and strong, can be moulded when hot and brittle when thin.
82
How is glass made?
The majority of glass is made by heating limestone, sand and sodium carbonate until they melt.
83
What is a composite?
They are made of one material (the reinforcement) embedded in another (the matrix). The properties depend on the material it is made from.
84
What is fiberglass and what are its properties?
It has a low density (like the polymer) but is very strong (like the glass).
85
What is concrete and what are its properties?
It is made from aggregate (a mix of sand/gravel) embedded in cement.
It has a high compressive strength.
86
What are the properties of polymers in general?
Polymers are adaptable - they are flexible and easily moulded.
They're often cheaper than other materials, and tend to be less dense.
They're thermal and electrical insulators.
They can degrade and break down over time.
87
What are the properties of ceramics in general?
They are insulators of heat and electricity.
They are brittle and stiff, but strong and hard wearing.
They don't degrade or corrode.
88
What are the properties of composites in general?
They have different properties depending on the matrix/binder.
They can be designed to have specific properties for a purpose.
They are very expensive.
89
What is a homologous series?
A group of chemicals that have similar chemical structures.
90
What are alkanes?
A homologous series of hydrocarbons - they contain just carbon and hydrogen atoms.
91
What are the bonds in alkanes?
Covalent bonds
92
What are the first 4 alkanes?
Methane, Ethane, Propane and Butane
93
What is the general formula for alkanes?
CₙH₂ₙ₊₂
94
What happens in a complete combustion reaction involving alkanes?
During a complete combustion reaction, they burn in oxygen to form carbon dioxide and water.
95
What happens in an incomplete combustion reaction involving alkanes?
Incomplete combustion happens in a limited supply of oxygen. Carbon monoxide is produced.
96
What are Alkenes?
A homologous series of hydrocarbons with at least one carbon-carbon double bond.
97
Why are Alkenes known as unsaturated?
They can make more bonds - the double bond can open up, allowing the two carbon atoms to bond with other atoms.
98
What are the first four Alkenes?
Ethene, Propene, Butene and Pentene
99
What is the general formula of Alkenes?
CₙH₂ₙ
100
How can you test for an Alkene?
With bromine water. When added to bromine water, an alkene will change it from orange to colourless. This is because the double bond opens up and forms bonds with the bromine.
101
What is hydrogenation?
Alkenes can react with hydrogen in hydrogenation. The hydrogen reacts with the double-bonded carbons and adds across the double bond.
102
What is the general formula of Alcohols?
CₙH₂ₙ₊₁OH
103
Where is the O-H drawn in an alcohol?
It's normally bonded to the last carbon.
104
What are the first 4 Alcohols?
Methanol, Ethanol, Propanol, Butanol
105
What happens when an alcohol is oxidised?
It forms a carboxylic acid. The process requires an oxidising agent.
106
What is the general formula of carboxylic acids?
Cₙ₋₁H₂ₙ⁻₁COOH
107
What are the first four carboxylic acids?
Methanoic acid, Ethanoic acid, Propanoic acid, Butanoic acid
108
What are polymers?
They are made up of lots of small molecules called monomers.
109
What are unsaturated compounds?
Molecules with at least one double covalent bond between carbon atoms.
110
What are saturated compounds?
Molecules with only single bonds between carbon atoms.
111
What is addition polymerisation?
It is when lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains.
112
What is the formula of a polymer formed by addition polymerisation?
You put the formula of the monomer in brackets with an "n" after it. eg. (C₃H₆)ₙ
113
What is an initiator?
It's a chemical added to alkenes so that they can polymerise.
114
What other conditions are needed for alkenes to polymerise?
It may need to be heated.
115
What is condensation polymerisation?
It involves two different types of monomer. They react together and they form poylmer chains. Each monomer has to contain at least 2 functional groups.
116
What happens to the 2 functional groups in each monomer in condensation polymerisation?
Each functional group can react with the functional group of another monomer, creating long chains of alternating monomers.
117
What is lost in condensation polymerisation?
For each bond that forms, a small molecule such as water is lost.
118
What are examples of condensation polymers forming?
Polyamides are mdae from carboxylic acid and amine monomers.
119
What are some naturally occurring important polymers?
DNA, amino acids and carbohydrates
120
Describe the polymer DNA
It contains 2 strands of nucleotide monomers that bond in a polymerisation reaction. There are 4 different monomers - A/T/G/C
121
Describe the polymer Amino Acid
Amino acids form polymers known as proteins via condensation polymerisation.
122
Describe the polymer Carbohydrate
They are molecules containing carbon, oxygen and hydrogen, producing by living things for energy.
123
How is crude oil formed?
It is formed from the buried remains of plants and animals. Over millions of years, with high temperature and pressure, the remains become crude oil.
124
What is crude oil?
A mixture of lots of different hydrocarbons. It's mainly made up of fractions with the formula CₙH₂ₙ - alkanes.
125
How are the different compounds in crude oil separated?
By fractional distillation.
126
What happens to the oil in crude oil during fractional distillation?
The oil is heated until most of it becomes gas. The gases enter a fractionating column. In the column, it's hot at the bottom and gets gradually cooler as it goes up.
127
What happens to the liquid part of crude oil during fractional distillation?
It's known as bitumen and is drained off at the bottom.
128
What happens to the longer hydrocarbons during the fractional distillation of crude oil?
They have high boiling points and turn back into liquids and drain out of the column early on in the process.
129
What happens to the shorter hydrocarbons during the fractional distillation of crude oil?
They have lower boiling points, and so turn to liquid and drain out much later on.
130
How is the crude oil mixture spread across the fractionating column?
It's separated out into different fractions, each of which contains a mixture of hydrocarbons with similar boiling points.
131
What is the order of fractions in the fractional distillation of crude oil (coolest to hottest)?
```
LPG (liquefied petroleum gas)
Petrol
Naphtha
Kerosene
Diesel
Oil
Bitumen
```
132
What is liquefied petroleum mostly made of?
Butane and Propane
133
What is naphtha?
It is used as a raw material in industrial processes.
134
What are the two important bonds in crude oil?
The intermolecular forces of attraction between different hydrocarbon molecules.
135
What does crude oil provide?
The energy needed for vital parts of modern life such as generating electricity and heating homes.
136
What does oil provide?
The fuel for modern transport - cars, trains, planes etc. It also provides raw materials needed for various chemicals, including plastics.
137
What is the problem with using crude oil?
The supplies are limited and non-renewable - one day we'll run out.
138
What are alternatives to oil?
Nuclear or wind power to generate electricity, ethanol to power cars and solar energy to heat water.
139
What is cracking?
A form of thermal decomposition which turns long alkane molecules into smaller alkane and alkene molecules which are more useful.
140
What is thermal decomposition?
When one substance breaks down into at least two new ones when you heat it. It requires lots of heat to break strong covalent bonds.
141
How is cracking used after the fractional distillation of crude oil?
A lot of the longer molecules from the fractional distillation are cracked into smaller ones as there is more demand for products like petrol.
142
How does cracking happen?
Vaporised hydrocarbons are passed over powdered catalyst at between 400-700 degrees celsius and 70 atmospheres. The long-chain molecules split on the surface of the catalyst.
143
What is the catalyst often used in cracking?
Aluminium oxide
144
Why does hydrogen reacting with oxygen give out energy?
Hydrogen and oxygen react to produce water. This reaction is exothermic - when new bonds are formed the excess energy is given out as heat.
145
What is a fuel cell?
An electrical cell that's supplied with a fuel and oxygen and uses energy from the reaction to produce energy efficiently.
146
What is the electrolyte and electrodes used in hydrogen-oxygen fuel cells?
The electrolyte is usually potassium hydroxide. The electrodes are usually porous carbon with a catalyst.
147
Where do hydrogen and oxygen go in the fuel cell process?
Hydrogen goes to the anode compartment and oxygen goes to the cathode compartment.
148
How is dealing with fuel cells different to electrolysis?
In electrolysis, the anode is the positive electrode and the cathode is the negative electrode. In fuel cells, it's the other way around.
149
What happens at the negative electrode in a fuel cell?
H₂ → 2H⁺ + 2e⁻
150
Where do the H⁺ ions go in a fuel cell?
To the positive electrode.
151
What happens at the positive electrode in a fuel cell?
O₂ + 4e⁻ + 2H₂O → 4H₂O
152
What happens to the electrons in a fuel cell?
They flow through an external circuit from the anode to the cathode - this is the electric current.
153
Why is the reaction in a full cell redox?
There is reduction at the cathode and oxidation at the anode, so it is redox.
154
What are the advantages/disadvantages of fuel cells?
It would be expensive to adapt current technology to run off fuel cells.
155
What is Phase 1 of the Earth's atmosphere?
When things settled down, the early atmosphere was mostly CO₂ and water vapour.
156
What is Phase 2 of the Earth's atmosphere?
N₂ isn't very reactive so it wasn't being broke down.
157
What happened during Phase 2 of the Earth's atmosphere involving green plants?
The oxygen in the air buil tup and much of the CO₂ got lucked up in fossil fuels and sedimentary rock.
158
What is Phase 3 of the Earth's atmosphere?
The oxygen also created the ozone layer, which blocked harmful rays from the sun.
159
What is the current composition of the earth's atmosphere?
78% nitrogen and 21% oxygen
160
Why does the human population affect the amount of carbon dioxide in the atmosphere?
More people are respiring, giving out carbon dioxide.
161
Why does the rise in human population affect use of energy?
More energy is needed for lighting, heating, cooking, transport, etc. This means the average energy demand per person is also increasing.
162
How does the increase in average energy demand per person affect the carbon dioxide in the atmosphere?
The increased energy consumption is mainly from burning fossil fuels, which release carbon dioxide.
163
How does the demand for land affect the amount of carbon dioxide in the atmosphere?
Deforestation occurs as a result of the human demand for land. But plants are the main things taking carbon dioxide out of the atmosphere, so less plants mean less in taken out.
164
What type of radiation does the sun give out?
Electromagnetic
165
What happens to the sun's electromagnetic radiation with short wavelengths?
It is absorbed by the Earth, warming the planet.
166
What is the greenhouse effect?
Some IR radiation is emitted to space.
167
What does the greenhouse effect do?
The absorption and reflection of IR radiation by greenhouse gases is what keeps the Earth warm.
168
What are greenhouse gases?
Greenhouse gases are the gases in the atmosphere that can absorb and reflect heat radiation. Carbon dioxide, water vapour and methane are three greenhouse gases.
169
What happens if the concentration of greenhouse gases increases?
You get an enhanced greenhouse effect - more heat radiation from the earth is absorbed and less is emitted to space. This causes the atmosphere to heat up.
170
What has happened to the level of methane in the atmosphere in recent years?
It has risen, which is an issue as it's a super effective greenhouse gas.
171
Most of the scientific community see global warming as anthropogenic - what does this mean?
Caused by humans
172
How can we try to reduce carbon dioxide emissions?
We can try to limit our own use of fossil fuels. This could be doing things like walking/cycling, or turning your central heating down.
173
What is global warming and what does it cause?
A type of climate change that causes other types of climate change - eg. changing rainfall patterns, flooding
174
What has the UK government done to combat the use of fossil fuels?
They have made plans to encourage the public and industry to become more energy efficient and use renewable energy.
175
How is Ethanol produced?
Through the fermentation of plants.
176
What are the pros and cons of Ethanol as an alternative to fossil fuels?
Pros - the carbon dioxide released when it's burned was taken in by the plant as it grew, so it's "carbon neutral". The only other product is water.
Cons - engines have to be changed to work with ethanol fuel. Ethanol fuel isn't widely available.
177
What are the pros and cons of Biodiesel as an alternative to fossil fuels?
Pros - it is "carbon neutral". Engine's don't need to be converted. It produces less pollutants than petrol or diesel.
Cons - we can't make enough to replace diesel. It's expensive to make.
178
How could Ethanol and Biodiesel increase food prices?
Farmers may switch to growing crops rather than harvesting livestock, which would lower the availability of food.
179
Other than carbon dioxide, what else is created from burning fossil fuels?
Sulfur dioxide and various nitrogen oxides.
180
What happens when sulfur dioxide and nitrogen oxides mix with clouds?
They form dilute sulfuric acid and nitric acid which falls as acid rain.
181
What does acid rain cause?
It kills trees and damages limestone buildings and stone statues. It also makes metal corrode.
182
What is photochemical smog?
A type of air pollution caused by sunlight acting on oxides of nitrogen. These oxides combine with oxygen in the air to produce ozone.
183
What can ozone cause?
Breathing difficulties, headaches and tiredness.
184
What can carbon monoxide do?
It can stop your blood doing its proper job of carrying oxygen around the body, which can lead to fainting, a coma or even death.
185
When and how is carbon dioxide formed?
One way it is produced is by incomplete combustion in petrol/diesel engines.
186
What is particulate carbon?
During incomplete combustion, small pieces of solids, particulates, can be released. They float around in the atmosphere and then fall to the ground, depositing themselves as soot.
187
What can particulate carbon cause?
It reduces air quality and can cause/worsen respiratory problems.
188
How is water important industrially?
It is used as a cheap raw material, a coolant and a solvent - between half and 2 thirds of fresh water in the UK is used in industry.
189
Where does water come from in the UK?
Groundwater: aquifers (rocks that trap water underground).
190
What does the availability of water depend on?
Annual rainfall
191
How pure is groundwater/surface water?
Groundwater from aquifers is usually quite pure, but surface water needs a lot of treatment.
192
What are the 4 stages of water purification?
Filtration
Sedimentation
Chlroination
193
What is the filtration stage of water purification?
A wire mesh screens out large twigs etc. and then gravel and sand beds filter out any other solid bits.
194
What is the sedimentation stage of water purification?
Iron sulfate or aluminium sulfate is added to the water, which makes fine particles coagulate and settle at the bottom.
195
What is the chlorination stage of water purification?
Chlorine gas is bubbled through to kill harmful bacteria/other microbes.
196
What pollutants can still be found in tap water?
Pesticide residues - sprayed too close to rivers/lakes.
197
What are the harmful affects of nitrate/lead?
Lead - can be poisonous
198
How is seawater changed into fresh water?
It is distilled, although this requires loads of energy and so it's really expensive.
