C14: The Earth's resources Flashcards
What do humans use resources for?
To provide warmth, shelter, transport and food.
How are resources that we need produced in many cases?
Agriculture - helps us use the Earth’s resources more efficiently. e.g. grow wood for timber or biofuels.
What is an example of chemistry replacing natural materials for synthetics ones?
Rubber - natural rubber comes from tree sap, but synthetic rubber is produced from crude oil. 2/3 of the world’s rubber is synthetic.
What does finite mean?
Natural resources which cannot be replaced as quickly as they’re being used up.
What are some examples of finite resources?
e.g. fossil fuels (humans use millions of kgs of fossil fuels everyday, which is much quicker than the rate at which fossil fuels form, meaning they will eventually run out.)
Metals - huge amounts extracted from the crust, continual usage means they will run out.
What does renewable mean?
Resources that we can replace as quickly as they are used - will never run out.
What are some examples of renewable resources?
Wood
What is sustainability?
The ability for humans to meet their needs without preventing future generations from meeting theirs.
How does chemistry allow us to become more sustainable?
Artificial fertilisers allows us to grow more food with the land available.
Helps provide water that is safe to drink (potable).
Processes like phytomining and bioleaching help extract metals more efficiently.
What traits must drinking water have in order to be safe?
Low levels of dissolved salts e.g. sodium chloride.
Low levels of microbes.
What is potable water?
Water that is safe to drink.
Why is potable water not the same as pure water?
Pure water contains no dissolved substances at all (only consists of h2o molecules) whereas potable water can contain small amounts and still be drinkable.
What is the main source of potable water in the UK?
Rainwater - low levels of dissolved substances.
Collects in the ground in aquifers, as well as in lakes, rivers and reservoirs. - sources of fresh water.
How is potable water produced from rainwater?
Choose a good source of fresh water.
Pass the water through filter beds to remove materials such as leaves or suspended particles (large particles). Water is sterilised to kill microbes using chlorine, UV or ozone. No need for distillation due to the already low amount of dissolved minerals (smaller particles)
How can potable water be produced from sea water (where countries don’t have access to fresh water)?
Sea water has high levels of dissolved minerals (potable water is produced through desalinisation). One way of carrying out desalination is using distillation. Another is to pass the water through partially permeable membranes (reverse osmosis).
These reduce the levels of dissolved substances.
Compare distillation to reverse osmosis
Both methods require large amounts of energy - expensive
What is water used for?
Small percentage for drinking.
Large amount for personal hygiene (baths and showers).
Flushing toilets and washing clothes.
Agriculture.
Why does waste water need to be treated before being released into the environment?
Contains a large amount of dissolved substances (e.g. urine and faeces).
Large number of harmful microorganisms.
- must be carefully treated.
Describe the process of treating waste water
- Sewage is screened by passing through a mesh (removes solids and pieces of grit.
- Sewage settles in large sedimentation tanks, producing a liquid effluent and a semi-solid sludge (sinks). Sludge is taken away and digested by anaerobic bacteria (in the absence of oxygen, these bacteria produce biogas, which can be burned for electricity.
Digested sludge can be used as fertilisers for farming. - Liquid effluent contains large amounts of organic molecules and harmful microorganisms, which need to be reduced before water is returned to the environment. Air is bubbled through the liquid effluent (allows aerobic bacteria to multiply), in the presence of oxygen, the aerobic bacteria digest organic molecules and harmful microorganisms.
- Liquid effluent is safely discharged into nearby rivers or the sea.
How is water from industrial waste treated?
Harmful chemicals first need to be removed. After, water can sagely enter general sewage treatment.
Sometimes treated sewage water is used directly to produce potable water
What are 3 sources of water?
Groundwater
Saltwater
Wastewater
What is the easiest way to produce potable water?
Using groundwater from aquifers (safe to drink once treated with chlorine).
* aquifers can sometimes be polluted e.g. with fertilisers from farms. So water needs to be tested carefully.
What are the negatives of making potable water directly from sewage?
Takes many purification steps - so only done in places where water is scarce
What are the negatives of making potable water from seawater?
Needs to be desalinated (lots of energy and money)
Why is there a demand for copper?
Used in electronic equipment (e.g. phones)
When is it economical to extract a metal?
When its ore contains enough metal.
Less economical to extract a metal from a low grade ore because it contains a small amount of the metal.
Why are we going to have to extract copper from low-grade ores?
Copper is scarce.
What is a low-grade ore?
An ore which contains a very small amount of a metal.
Describe the process of phytomining
- Plants are grown on land containing the metal compound that we want. Plants absorb the metal compound and concentrate it in their tissue.
Plants are harvested and burned, and the ash contains a relatively high concentration of the metal compound.
Describe the process of bioleaching
Uses bacteria
Bacteria are mixed with low-grade ore. They carry out chemical reactions and produce a solution called a leachate, which contains the metal compound that we want
What do you need to do after the processes of bioleaching and phytomining?
Extract the metal from the metal compound produced.
- in the case of copper, we can displace copper using iron because scrap iron is cheap and more reactive than copper. Copper can also be extracted using electrolysis.
What are some points about the processes of phytomining and bioleaching?
Allow us to economically extract metals from low-grade ores (important as Earth’s metal ores are limited).
Do not involve digging, transporting or disposing of large amounts of rock (unlike traditional mining)
What is a life cycle assessment?
Attempts to put a number on the environmental impact of a product.
What are the 4 main stages of lca?
Environmental impact of extracting and processing raw materials.
Packaging, manufacturing and transportation.
Impact of product during its lifetime.
Disposal of product at the end of its useful life
Give some examples for stage 1 of the lca
Plastics - come from crude oil, which is extracted from the ground and transported to oil refineries. Hydrocarbons are separated and cracked. - processes take a large amount of energy, which is generated by fossil fuels which leads to climate change.
Metals - takes huge amount of energy. Ore is dug out of the mine and transported for processing. Metal is extracted from the ore, producing waste products
Give an example for the environmental impact of a product at the end of its useful life
Many products have harmful chemicals which need to be disposed of carefully, which can take lots of energy.
Compare the lca for plastic and shopping bags
Plastic - produced from crude oil (non-renewable, can harm habitats if there is an oil spill, chemically processed (lots of energy + waste))
- Strok, can be reused
- Transported to landfills - lighter
- Plastic is non-biodegradable, not broken down by microorganisms - remain in environment for a long time, so major form of litter and fill up landfills
Paper - made from wood from trees (renewable, destructive to forests, chemically processed, requires huge amounts of water)
- Weak, tear easily.
- Transported to landfills - heavier so take more energy
- Breaks down quickly
What are some of the issues of lca?
Can measure use of water and energy, can also measure the production of some waste products.
Cannot always be certain of how damaging these are to the environment.
In some cases, we have to make estimates or value judgements which are not always accurate.
LCA can be biased (to support claims by advertisers)
How are raw materials often obtained?
Through quarrying or mining- harmful to environment.
Takes lots of energy to convert raw materials into useful products.
What are the negatives of quarrying and mining?
Quarrying - large amounts of dust and destroys habitats.
Mining - Release harmful chemicals into environment.
Why is recycling good?
Saves limited resources and energy.
Reduces the amount of waste that we produce and has a less harmful effect on environment.
How are metals recycled?
They are melted, then recast into different products
What are the problems with recycling metals?
They usually need to be separated before being recycled (depends on the properties of final product)
