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
Cons of getting raw materials
How & Why is it important we recycle?
- Quarrying produces large amounts of dust and destroys habitats.
- Mining can release harmful chemicals
It is very important that we recycle as it helps save limited resources and energy while reducing the impact of waste on the environment as there is less waste.
Some products like glass bottles can be reused and can be crushed and melted to make different products.
Whereas some products can be recycled for a different use like plastic bottles which can be recycled to make fleece jackets or carpets.
Metals can be recycled by melting and recasting them. But different metals need separating but it depends on the properties of the final product.
What is corrosion?
Why is corrosion a problem?
What is Coating and what are the different types?
Corrosion is the destruction of materials by chemical reactions with substances in the environment.
e.g. Rusting only in Iron and its alloys(steel). In the case of other metals use corroding.
Corrosion is a big problem as it damages materials
But it can be stopped using a barrier and to do that we use grease or paint or coat the material with a metal(Electroplating).
The surface of aluminium naturally reacts with oxygen in the air to form a thin layer of aluminium oxide which protects the metal underneath.
Coating a metal with zinc is called galvanising. These are galvanised nails. This is a barrier but if it gets scratched then it prevents corrosion as zinc is more reactive than iron. This means the zinc corrodes instead of the iron. This is called **Sacrificial protection**.
How to carry out experiement for conditions of corrosion?
What is an alloy?
An alloy contains a metal blended with other elements. They tend to be harder than pure metals as the layers cannot slide over due to the varying sizes in the atoms.
- Alloys are mixtures of metals where the metals are not chemically combined
- They can also be made from metals mixed with non-metals.
- Alloys often have properties that can be very different from the metals they contain.
What are these alloys made of and what are their uses?
BRONZE
BRASS
GOLD
STEEL
ALUMINIUM
- Bronze is an alloy of copper and tin. It is extremely hard and tends not to corrode so it is used in statues
- Brass is an alloy of copper and zinc. Even though it is harder than pure copper it can still be formed into different shapes so it is ideal for musical instruments and door handles
- Gold is used for jewellery. But pure gold is too soft so it is alloyed with silver, copper and zinc to make it harder. The purity is rated in carat 24 = 100%
- Steel is an alloy of iron containing specific amounts of carbon. It also contains other metals.
- High carbon steel is extremely hard but it is also brittle.
- Low carbon steel is softer and more easily shaped so it is used to make car bodies.
- But it can rust so to prevent that stainless steel which also contains chromium and nickel is made.
- Aluminium alloys are low density that makes them really useful in aeroplanes.
What are the two types of ceramics you need to know?
- *Glass**
- *Clay Ceramics**
How do you make borosilicate glass?
What is borosilicate glass used for?
Borosilicate glass has a higher melting point than soda lime glass. This makes it useful for objects that require heating.
- It is made by mixing
- Sand
- Boron Trioxide
