C10 - Using Resources Flashcards
What do we use the Earth’s Resources for?
What are these resources produced by?
- Shelter, Warmth, Food & Transport
In many cases, these resources are produced by agriculture provide food, timber, clothing and fuels.
e.g. Cotton from plants. Modern agriculture allows us to grow enough cotton to meet the needs of the world
Humans also plant trees which are used for timber or fuels. Many power stations run on biofuels like woodchips.
Agriculture helps us use the Earth’s resources efficiently
What are synthetic alternatives?
In some cases Chemistry has replaced natural resources with a synthetic alternative e.g. rubber as natural rubber comes from the sap of tree whereas synthetic rubber is produced using crude oil.
Finite Resources
Some natural resources are finite like fossil fuels. Humans use millions of kilograms of fossil fuels every day. But fossil fuels are produced very slowly so we will end up using them all up.
Metals are also a finite resource. They are extracted from the Earths crust and if we keep using them they will run out.
Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials.
Renewable Resources
e.g. wood. We can replace these resources at the same rate which we use them. They will not run out.
Why should we make sure human activities are sustainable and what role does Chemistry play in this?
It is really important that human activities are sustainable. We can meet our needs without jeopardizing the future generations.
Chemistry plays a huge role in this. E.g. Artificial fertilisers allow us to grow more food with the land available. It also provides safe drinking water. Furthermore, processes such as Phytomining and bioleaching help us extract metals more easily.
What do scientists call potable water and how is it different to pure water?
Drinking water has to have low levels of dissolved salts and cannot have high levels of microbes like bacteria. Scientists call water which is safe to drink **potable water**.
Potable water is not equal to pure water as pure water contains no dissolved substances at all whereas potable water does contain dissolved substances but a low level of them.
Where does the UK get their potable water from?
What do countries that do not have fresh water do?
In the uk rain water provides most of our potable water as it has low levels of dissolved substances. It gets collected in the ground in aquifers, lakes, rivers and reservoirs so they are good sources.
In the uk we have access to lots of fresh water which has low levels of dissolved minerals but in many places this is not the case.
Their water might be filled with large amounts of dissolved substances like salts. In this case, Desalination is required to make the water potable. This reduces the levels of dissolved minerals to an acceptable level. Two ways to do this are distillation and reverse osmosis. This is very expensive.
How do we produce Potable water?
- You need a good source of fresh water
- Then pass the water through filter beds. That is to remove materials such as leaves and suspended particles.
- Finally, the water is sterilised to kill microbes. In the UK we use chlorine. But in some parts of the world, ozone or UV light is used.
Why do we treat waste water?
How do we treat Waste Water?
Waste water contains large amount of organic molecules and contains harmful microorganisms so the waste water must be carefully treated. To do this we:
- The sewage is screened by passing it through a mesh as this removes solids and pieces of grit.
- Now the sewage will settle in large sedimentation tanks. This produces a liquid effluent and a semi-solid sludge which sinks.
- The sludge is taken away and digested by anaerobic bacteria and in the absence of oxygen, they produce biogas which can be burned for electricity
- At the end, digested sludge can be used for fertilisers in farming
- The liquid effluent contains large amounts of organic molecules and harmful microorganisms both of these need to be reduced.
- Therefore, air is bubbled through the liquid effluent. This allows aerobic bacteria to multiply and with the presence of oxygen these bacteria will digest organic molecules and harmful microorganisms.
- Then the liquid effluent can be safely discharged into nearby rivers or the sea.
How is potable water produced in other countries?
What is the easiest way to produce potable water?
In some parts of the world, treated sewage is used directly to produce potable water. However this takes many steps and is only done in areas where water is scarce. Salt water needs to be desalinated.
The easiest way to produce potable water is to use ground water from aquifers. Once treated with chlorine they are safe to drink, but they can sometimes be polluted by fertilisers so water needs to be tested.
How are most ores found?
Why are ores becoming Scarce?
What are ores used for?
What are the two ways to extract metals from low-grade ores?
Most metals found in the Earth are already reacted with other elements like oxygen.
But the worldwide demand for metals is growing. They’re ores are extracted from mines. But ores are becoming scarce so we will have to extract copper from low-grade ores(they contain small amounts of the metal).
e.g. copper for electronics and phones.
- Phytomining
1. This involves growing plants on land containing the metal compound we want.
2. These plants absorb the metal compound into their tissue.
3. They are then harvested and burned.
4. At the end the ash contains a relativley high concentration of the metal compound. - Bioleaching
1. Bacteria are mixed with low grade ore
2. Then the bacteria carry out chemical reactions and produce a soloution called leachate. That contains the metal we want.
What do we do at the end of both Phyto mining and Bioleaching?
Why do we need these methods?
Once the copper compounds have been extracted they can be broken down by displacing or electrolysis.
For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron(scrap Iron is cheap) or by electrolysis
These methods avoid traditional mining methods of digging, moving and disposing of large amounts of rock.
What is an LCA
A LCA are carried out to assess the environmental impact of products.
Examples of LCA’s
- Extracting metals also takes a large amount of energy as ore has to be dug out of the mine and transported for processing.
- Then the metal has to be extracted from the ore and this can produce large amounts of toxic waste products.
- Once this is done, we have to manufacture, package and transport our product.
- All these stages require energy and can produce harmful products
- First, the oil has to be extracted and then transported to the refineries.
- Then they have to be separated and cracked
- Finally the polymer is produced
- All of these processes take a large amount of energy and alot of the energy will be generated by burning fossil fuels which leads to climate change.
What are the four stages of life cycle assessments?
- A life cycle assessment (LCA) is an analysis of the overall environmental impact that a product may have throughout its lifetime
- The cycle is broken down into four main stages which are:
- extracting and processing raw materials
- manufacturing and packaging
- use and operation during its lifetime
- disposal at the end of its useful life, including transport and distribution at each stage.
Diagram showing the four stages in a life-cycle assessment
- 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
- Manufacturing processes also have an impact on the environment which may include:
- Using up land for factories
- The use of fossil fuelled machines for production and transport
- Usage of a product may also affect the environment although it depends on the type of product
- For example, a wooden desk has very little impact whereas a car will have a significant impact (air pollution)
- The disposal of outdated products has an impact on the environment which may include:
- Using up space at landfill sites
- Whether the product or its parts can be recycled
- A life cycle assessment is carried out using the data of a given product and the criteria of the assessment
- Rarely is there a perfect product with zero environmental impact, so often a compromise is made between environmental impact and economical factors
Disadvantages of LCA’s
Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg in support of claims for advertising purposes.
Paper shopping bags vs Plastic shopping bags.
- 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 usage of the item:
- If the 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
How to carry out experiement for conditions of corrosion?
What is a polymer.
What do their properties depend on?
How do you change the properties?
- Depending on the manufacturing process used, the same polymer can have different properties
-
Polythene for example can be made at very high pressure and moderate temperature
to produce low density (LD) polythene which is used for bags and bottles where flexibility is needed - If it is produced at lower temperatures and pressures and with the use of a catalyst,
- *a much higher density (HD) polythene is produced.** This polymer has a more rigid, solid structure and is used to produce water tanks, mouldings, drain pipes etc
Thermosetting Polymers
Thermosetting polymers do not melt when heated. They tend to char and burn when heated, but they are resistant to much higher temperatures than thermosoftening plastics. They are used to make electrical plugs, which must not melt, even if there is a malfunction and the wiring inside gets hot.
Thermosetting polymers have strong cross-links between monomers on different polymer chains that hold the structure together. These are strong and rigid structures that don’t soften under heating
Thermosoftening polymers
Thermosoftening polymers melt when heated.
They can be reshaped when soft.
They go back to a solid when cooled down. Most plastics that we come across in everyday life are thermosoftening plastics.
This means that they can be recycled, which involves melting them before making a new product.
- Thermosoftening polymers consist of weak intermolecular forces holding the polymer chains together
- These polymers therefore have low melting points, can be melted and remoulded to form different shapes
What is the Haber process used for?
What is the equation for the Haber process?
It is used manufacture ammonia, which can be used to produce nitrogen-based fertilisers.
The raw materials for the Haber process are nitrogen and hydrogen
Le Chatelier’s principle
A cool temperrature makes the reaction slow as the equilibrium will shift to the left.
What are NPK fertilisers?
How are NPK fertilisers produced?
What do they contain?
They are important fertilisers which contain
Nitrogen, Phosphorus, Potassium
NPK fertilisers are formulations of various salts containing appropriate percentages of the elements needed by the plants are formulations produced in Industrial Facilities
How do we make ammonium nitrate for NPK fertilisers?
How do we get the potassium for NPK fertilisers?
The main compound of nitrogen in NPK is ammonium nitrate (NH4NO3) it is made by reacting Ammonia with nitric acid.
Potassium - Potassium chloride, potassium sulfate are obtained by mining, but phosphate rock cannot be used directly as a fertiliser whereas the other two can.
What are the different ways to produce Phosporus for NPK?
What is the difference of producing ammonium nitrate in the school vs lab?
Phosphate rock can be extracted by mining. It has to be chemically processed.
Nitric acid - By treating Phosphate rock with nitric acid produces phosphoric acid and calcium nitrate. But phosphoric acid contains phosphorus but we cannot add this directly to plants so we neutralise it with ammonia to make ammonium phosphate which can be used.
Sulfuric acid - If we treat phosphoric rock with sulfuric acid we make a mixture of calculim phosphate and calcium sulfate. This is called single superphosphate
Phosphoric acid - If we treat phosphate rock with phosphoric acid we make triple superphosphate.
What are the stages of the Haber Process?
Ammonia is manufactured using the Haber Process which occurs in five stages
The reactants are hydrogen and nitrogen which are extracted from methane and the air respectively
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 catalytic iron beads 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)
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
What is the difference between the laboratory and Industrial method of making ammonium sulfate?
In industry 1000s of kgs of ammonia are produced in quickly. This is a continuous process whereas in schools it is produced in small amounts in one go called batch processes.
In industry concentrated nitric acid and ammonia is used as a gas. This is very dangerous as the reaction is very exothermic and produces heat which is used later on. Whereas in schools dilute acid and small amounts of ammonia are produced which is safe. Instead a bunsen burner or a water bath is used.
