Using resources 1 Flashcards
Corrosion, alloys as useful materials, Earth's resources/sustainable development, LCAs.
Corrosion
The destruction of materials by chemical reactions with substances in the environment.
Rusting
The corrosion of iron by reacting with oxygen and water.
What is the word equation for rusting?
Iron + Water + Oxygen → hydrated iron (III) oxide
What do we mean by saying iron is hydrated?
Water molecules are part of the structure.
What is the symbol equation for rusting?
4Fe + H₂O + 3O₂ → 2Fe₂O₃*H₂O
Half equation for rusting (iron)
Fe → Fe³⁺ + 3e⁻
Half equation for rusting (oxygen from the surroundings)
O₂ + 4e⁻ → 2O²⁻
How is rusting an example of a redox reaction?
Iron atoms lose (3) electrons (are oxidised) and oxygen atoms gain (2) electrons (are reduced).
What are the conditions required for rusting?
Water and oxygen must be present.
How can we prevent corrosion?
Applying a coating that acts as a barrier:
-Painting
-Greasing
-Electroplating
-Galvanising
-Sacrificial protection
Painting or greasing
The iron object is coated with layers of paint or grease.
Painting or greasing explanation.
This prevents rusting because the layer acts as a barrier, preventing oxygen or water reaching the iron to react.
Electroplating explanation
This prevents rusting because the layer acts as a barrier, preventing oxygen or water reaching the iron to react.
Electroplating
Electrolysis is used to coat the iron object in a thin layer of another metal.
-The (negatively charged) cathode is the object to be plated
-The (positively charged) anode is the plating metal
-The electrolyte contains ions of the plating metal
Sacrificial protection
Blocks of a metal more reactive than iron (e.g. Magnesium) are attached to an iron object.
Sacrificial protection explanation
The more reactive metal will oxidise in preference to the iron so the iron won’t rust.
Galvanising
The iron object is dipped in molten zinc, giving it a coating of zinc.
Galvanising explanation
The zinc forms a protective coating, but if this coating gets scratched, and the underlying iron is exposed, the zinc will oxidise in preference to the iron (as it’s more reactive).
What determines the reactivity of elements?
How easily they form ions: more reactive metals form ions more easily.
In experiments, how can we tell if an iron object has rusted?
Measure the mass of the iron object before and after it is kept in certain test tube conditions for a specified period of time. If the iron has rusted, mass will increase.
How can an iron object break down completely?
The surface metal rusts, but this flakes off after a time, leaving the next layer of iron exposed to water and oxygen. This layer then rusts and flakes: the process repeats until the iron object is broken down completely.
Corrosion of Aluminium
Only the surface atoms are affected. The top layer of Al atoms is oxidised to form Aluminium oxide (Al₂O₃) which acts as a protective layer for the rest of the Al from substances in the environment.
What does a layer of oil over water in a test tube do?
Stops new oxygen from the air dissolving into the water.
Why might we boil water in the test tube with the oil before an experiment testing for rust?
To remove any oxygen from the water.
Why might we put anhydrous calcium chloride crystals at the bottom of a test tube with oxygen in? (rusting experiment)
To remove any water vapour from the air.
What is an ore?
A rock containing enough metal to be economically worth extracting.
The Earth’s resources of metal ores are…
limited.
Give three disadvantages of extracting metals from the ground.
-Large amounts of waste go to landfill
-Noise and dust pollution from machines
-Destruction of habitats
What is a low grade ore?
A rock that contains a small percentage of a metal or its compound - not enough to be economically worth extracting (using traditional mining methods).
Which ores in particular are becoming scarce?
Copper ores.
Name alternative methods of extracting copper from low-grade ores
Bioleaching
Phytomining
Briefly describe the process of phytomining.
Plants are used to absorb metal compounds.
They are then harvested and burned to produce ash that contains metal compounds.
Describe the process of phytomining:
Plants are grown on a low-grade ore site.
Through active transport, they absorb copper ions from the soil/rock through their roots.
The plants are harvested and then burned to produce ash which will contain copper ions.
The ash is dissolved in water to form a copper solution.
Pure copper can then be extracted by displacement using scrap iron or by electrolysis.
Briefly describe the process of bioleaching.
Bacteria is used to produce leachate solutions that contain metal compounds.
Describe the process of bioleaching:
A low-grade ore site is flooded with bacteria.
These leech copper ions from the ground, then produce leachate solutions (containing the copper ions).
Pure copper can then be extracted by displacement using scrap iron or by electrolysis.
How can metal compounds be processed to obtain pure metals?
By displacement or electrolysis
e.g. copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis.
Why is extraction by heating with carbon expensive?
Carbon must be heated to high temperatures which requires lots of energy.
What is the ‘normal’ method of extracting metals?
Quarrying/mining
Why does iron displace copper from solutions of copper compounds?
It is more reactive so iron atoms become ions more easily than copper atoms.
What is the equation for the displacement of copper (from copper sulfate) with scrap iron?
CuSO₄ (aq) + Fe (s) → FeSO₄ (aq) + Cu (s)
Explain why the displacement of copper with scrap iron is a redox reaction.
Iron atoms are losing electrons to form 2+ ions and become part of the compound so are oxidised.
Copper ions are gaining 2 electrons to form copper atoms so are reduced.
What do humans use the Earth’s resources for?
To provide warmth, shelter, food, and transport.
What do natural resources provide? (give examples)
Food, timber, (cotton for) clothing, and (oil for) fuel.
What are natural resources?
Resources that form without human input. They include anything that comes from the earth, sea, or air.
What can natural products be replaced with or improved upon by?
Synthetic products
Man-made processes
What can rubber from tree sap be replaced with?
Man-made polymers (for uses such as in tyres).
Chemistry plays an important role in improving…
…agricultural and industrial processes to provide new products and in sustainable development.
Give an example of agriculture providing conditions where natural resources can be enhanced for our needs.
The development of fertilisers has meant we can produce high crop yields.
What is sustainable development?
Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.
Finite resources from the Earth, oceans and atmosphere are…
… processed to provide energy and materials.
Give an example of a finite resource.
Fossil fuels
Nuclear fuels such as uranium and plutonium
minerals and metals found in ores
What process is used to produce petrol from crude oil?
Fractional distillation
What happens to metal ores to produce pure metals?
They are reduced.
What must people balance when extracting raw, finite resources?
The social, economic, and environmental effects.
Positives of mining metal ores.
Useful products can be made
Provides jobs for local people
Brings money into the area
Negatives of mining metal ores.
Bad for the environment as…
The process uses loads of energy
Scars the landscape
Produces lots of waste
Destroys habitats
What two metals is bronze (alloy) made of?
Copper and Tin.
Alloy
A mixture of metals.
Uses of Bronze
sculptures, musical instruments
What two metals is brass (alloy) made of?
Copper and Zinc
What is the carat number of pure gold?
24
Uses of brass
It doesn’t tarnish so is useful for doorknobs and musical instruments.
What are steels?
Alloys of iron that contain specific amounts of carbon, and other metals.
Why are alloys of aluminium often used for trains and planes?
The alloys are low density (so lightweight) but strong.
Properties of low carbon steel
-Softer and more malleable (easily shaped)
-Will crumple e.g in a car crash lowering shock for passengers
Properties of high carbon steel
Strong but brittle
Types of steel
High carbon steel
Low carbon steel
Stainless steel
Why is gold rarely used in its pure form?
It is too soft so alloys are often used.
Properties of stainless steels
-Hard and resistant to corrosion
-Used in cutlery
Which elements do stainless steels contain?
chromium and nickel
What is gold used in jewellery usually an alloy with?
Silver, Copper, and Zinc.
What is the proportion of gold in an alloy measured in?
Carats.
What percentage of gold is there in an 18 carat gold item?
75%
What are the synthetic replacements for wool, cotton, and wood?
wool = acrylic fibre
cotton = polyester
wood = PVC and MDF composites
List some finite resources
coal
crude oil
natural gas
nuclear fuels
metal
List some renewable resources
leather
solar power
wood
cotton
ethanol
Suggest three reasons why copper should not be disposed of in landfill sites.
-Landfill sites are filling up
-Copper ores are limited
-Copper can be reused or recycled
It is now ___________ to extract copper from ___ _____ ____.
economical
low grade ores.
Suggest one reason why it is difficult to dispose of the waste rock from extraction of metals from their ores.
There are large amounts of rock to dispose of as waste.
What does copper sulfide react with oxygen to produce?
Sulphur dioxide.
What does sulfur dioxide cause?
-Acid rain.
-Harm to the lungs e.g. chest tightness or wheezing
Are energy resources likely to be renewable or non-renewable if they take a long time to form?
Non-renewable
Are energy resources likely to be renewable or non-renewable if they take a short time to form?
Renewable
What are resources with lower energy densities likely to be?
Less energetic fuels are likely to be renewable resources like timber.
What does LCA stand for?
Life cycle assessment.
What is the purpose of a life cycle assessment?
To assess the environmental impacts of products.
(in each of the four stages)
What are the four stages of a life cycle assessment?
- extracting and processing raw materials
- manufacturing and packaging
- use and operation during a product’s lifetime
- disposal at the end of a product’s useful life
In Life cycle assessments, what does the disposal stage include?
The transport and distribution of the product AT EACH STAGE.
When should LCAs be quantified?
Only where data is readily available for energy, water, resources, and wastes.
How can extracting raw materials damage the environment directly?
-Digging mines
-Cutting down trees
How can extracting raw materials damage the environment indirectly?
-Large amounts of energy required to process the materials
-Production releases pollution into the environment
The manufacturing and packaging of products can release pollution into the environment.
This pollution can include what?
Harmful/toxic fumes such as:
-Carbon Monoxide
-Hydrogen chloride
Name processes that require large amounts of energy at the ‘extracting and processing’ stage.
-Extracting metals from their ores
-The fractional distillation of crude oil
How can the manufacture and packaging of products damage the environment?
-Uses lots of energy resources
-Can release a lot of pollution
-Produces waste products which need to be disposed of
How can the amount of waste produced (at the manufacture and packaging stage) be reduced?
By turning some waste into other useful chemicals.
This reduces the amount of waste that ends up polluting the environment.
The chemical reactions used to make compounds from their raw materials can produce what?
Waste products.
What raw material is needed in the production of a plastic bag?
Crude Oil
What raw material is needed in the production of a paper bag?
Timber
Manufacturing and packaging of crude oil to produce a plastic bag.
-Hydrocarbons are extracted from the crude oil by fractional distillation
-Hydrocarbons are then cracked to make alkenes
-Alkenes undergo polymerisation to make plastics
Manufacturing and packaging of timber to produce a paper bag.
-Timber is pulped (broken up into pieces and soaked)
-Lots of waste is made
Using plastic bags
-Can be reused
-Multiple uses, e.g. shopping, bin liners
Using paper bags
-Used only once
Product disposal (plastic bags)
-Recyclable but not biodegradable
-Will take up space in landfill and pollute land
-Can harm animals e.g. choke them
Product disposal (paper bags)
-Biodegradable
-Non-toxic
-Can be recycled
What evidence is there from LCAs that plastic bags are less harmful to the environment than paper bags?
Even though plastic bags aren’t biodegradable, they take less energy to make and have a longer lifespan than paper bags.
How might the use of fossil fuels damage the environment?
-Burning fossil fuels releases greenhouse gases and other harmful substances into the environment
How might the use of fertilisers damage the environment?
-Fertilisers can leach into streams and rivers causing damage to ecosystems.
How can the length a product is used for affect the environment?
-Products that need lots of energy to produce but are used for a long time means less waste in the long run.
How might the disposal of a product damage the environment?
-Products disposed of in landfill sites take up a lot of space
-They might also pollute the land or contaminate water sources
-Energy is used to transport waste to landfill, causing pollutants to be released into the atmosphere
-Products might be incinerated which causes air pollution
Give an example of a disposed product contaminating water sources
Paint washing off a product and into rivers.
What does ‘incinerated’ mean?
Burnt
Use of water, some natural resources, energy sources and production of some wastes can be fairly easily what?
Quantified
Why is the effect of some pollutants hard to give a numerical value to?
-There are many different steps, making it difficult to gather all the required data about each
-It’s difficult to apply a value to the negative effects e.g. of plastic bags in the environment compared to paper ones
What are the problems with LCAs? part 1
-It’s hard to give a numerical value to the effects of some pollutants
-Producing an LCA is not an entirely objective method as it takes into account the values of the person carrying out the assessment (which means LCAs can be biased)
What are the problems with LCAs? part 2
-Selective or abbreviated LCAs can be written to deliberately support the claims of a company for advertising purposes and make them look more favourable. (these LCAs are biased)
-It’s hard to compare different harms e.g. is lung disease or global warming worse?
Sustainable development is an approach to what kind of development?
Human and economic
What is reuse?
Lengthening the life of an item by using it for a different purpose.
What is recycling?
The process of collecting and processing materials that would otherwise be thrown away, and turning them into new products.
It is _____________ to continue using non-renewable resources.
Unsustainable
Why is extracting materials unsustainable?
Due to the amount of energy used and waste produced.
Why is processing resources into useful materials e.g. glass/bricks unsustainable?
The processes often use energy that comes from finite resources.
Obtaining raw materials
from the Earth by quarrying and mining causes…
environmental impacts.
Give one way in which scientists are working to improve the sustainability of copper (finite resource).
Extracting it from low-grade ores using phytomining or bioleaching.
Alternative ways to extract metals evaluation.
The methods have a much smaller environmental impact but are slow.
Name some materials that are produced from, limited raw materials.
-Metals
-Glass
-Building materials
-Clay ceramics
-Most plastics
How can glass bottles be recycled?
They can be crushed and melted
-To make different glass products
-Or for a different use for example in insulating glass wool (for wall insulation in homes)
What usually happens before glass can be recycled?
The glass is separated by colour and chemical composition (type).
How can metals be recycled?
They can be melted and then re-casted or reformed into different products.
Suggest a way in which the amount of iron needed to be extracted from iron ore can be reduced.
Add scrap steel to iron from a blast furnace.
(or keep them together)
What does the amount of separation (into different elements) required for recycling depend on?
-The material
-The properties required of the final product
What happens in a blast furnace?
Iron is extracted from its ore at a high temperature using carbon.
The reduction in use of , reuse and recycling of materials by end users
reduces…
…the use of limited resources, use of energy sources, waste, and environmental impacts.
How can people reduce the use of finite resources?
-People can use less finite resources
-Chemists can develop and adapt processes so they use lower amounts of finite resources
How are the development of catalysts improving sustainability?
Catalysts reduce the amount of energy required for certain industrial processes.
How is using less finite resources sustainable?
-Reduces the use of that resource
-Reduces the use of any resources needed to produce it (e.g. fossil fuels which are burned for energy)
How is recycling metals sustainable?
-Uses less energy than is needed to mine and extract new metal
-Conserves the finite amount of each metal in the earth (e.g. reduces the need for copper-rich ores)
-Cuts down the amount of waste getting sent to landfill
Why is quarrying and mining metals unsustainable?
-The process requires lots of energy
-Which is usually obtained from burning fossil fuels
What things must be included in a full LCA?
-(source of) raw material
-packaging (e.g. the number of products packaged by box)
-energy usage (production, transportation, incineration
-average number of times product used/useful lifetime
-biodegradable?
-recyclable?
What are the key things to think about in the ‘raw materials’ stage of an LCA?
(mainly for comparison questions)
-are the resources renewable or finite?
-which product has higher energy costs? (it costs a lot to extract metals from ores, for example)
-wood may involve deforestation reducing biodiversity
What are the key things to think about in the ‘manufacturing and packaging’ stage of an LCA?
(mainly for comparison questions)
-How much energy is required?
(if heavier product/material this will be harder to transport - uses more fuel - so has a higher energy requirement)
-which uses more packaging?
-less packaging conserves raw materials
-if packaging is similar then neither has an advantage
What are the key things to think about in the ‘use and operation’ stage of an LCA?
(mainly for comparison questions)
-How often does each product need replacing?
-Single use? (If both products are single use then neither has an advantage)
-How often is each product disposed of? more or less often than the other?
What are the key things to think about in the ‘disposal’ stage of an LCA?
(mainly for comparison questions)
-Can each product be put to further use/ used to make new products? (this conserves energy and finite resources)
-will the product decompose or remain in landfill which is running out?
-Can it be recycled?
-Not recyclable so uses landfill which is running out?
-Could it release toxins on incineration?
Why should metals (these may be named e.g. iron/copper) be recycled?
-To conserve finite ores/ resources of (iron/ iron ore)
-to reduce the amount of landfill in sites which have limited space
-to avoid the need for mining which causes pollution
Suggest two reasons why metals are mixed with other metals (e.g. to make 9 carat gold rings)
-Harder
-Stronger
-More durable
-Aesthetic reasons
Suggest two reasons why objects (e.g. surfboards) are coated.
-Makes the object
-Hard
-Strong
-Durable
-Aesthetic reasons
Describe how ceramic food plates are produced from clay (2)
Wet clay is shaped and heated in a furnace.
What pieces of information about energy usage would make a full LCA?
Energy used in:
-Extraction of raw materials
-Processing raw materials
-Transportation
-Disposal
-Recycling
Conductivity
How well a material conducts electricity.
Strength
The ability of a material to resist an applied force (it is hard to change the shape of a strong material).
Hardness
How well a material can resist being scratched or indented (hard materials don’t scratch).
Brittleness
How easily a material breaks when a force it applied (brittle materials snap easily).
Stiffness
How well a material can resist bending (a stiff material won’t bend very much).
What does Phytomining and bioleaching avoid?
Traditional mining methods of digging, moving and disposing of large amounts of rock.
What are most metals in everyday life?
Alloys.
