C10 Flashcards
What do humans use the Earth’s resources for?
- energy and fuels (warmth)
- materials for building
- food through farming
- fuels for transport
- materials for clothing
What is sustainable development?
Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
What are finite resources?
From the Earth’s crust, oceans and atmosphere and they will eventually run out
Give an example of a finite resource
- crude oil
- fossil fuels
What is potable water?
Water that is safe to drink.
(It has sufficiently low levels of dissolved salts, microbes and minerals)
How is potable water obtained in the UK?
rain provides water with low levels of dissolved substances (fresh water) that collects in the ground and in lakes and rivers
The potable water is collected by:
- choosing an appropriate source for fresh water
- passing the water through filter beds
- sterilising
What sterilising agents are used for potable water?
- chlorine
- UV light
- ozone
What happens when the supplies of freshwater are limited?
Desalination of sea/salty water
- can be done by distillation or processes which involve membranes e.g. reverse osmosis
- (requires high amounts of energy)
Explain what happens during reverse osmosis
1.water is put under high pressure and passes through a membrane with tiny pores in it
2.the pores allow water molecules to pass through but prevent most ions and other molecules from passing through
What are disadvantages of reverse osmosis?
-expensive membranes
-produces a large volume of waste water (low efficiency)
What does sewage treatment involve?
- screening and grit removal
- sedimentation, which produces sewage sludge and effluent
- anaerobic digestion of sewage sludge
- the (light) effluent is treated with aerobic bacteria to reduce the volume of solid waste
How does mining damage the environment?
- landscape scars
- pollution
- habitat destruction
What are new ways of extracting copper from low-grade ores?
- Phytomining
- Bioleaching
Properties of copper:
- malleable
- unreactive
- conducts heat and electricity well
Explain phytomining
Uses plants to absorb metal compounds from contaminated land. The plants are harvested and then burned to produce ash (containing the metal compound)
Explain bioleaching
Uses bacteria to produce leachate solutions that contain metal compounds
bacteria are added to low grade ores and they then form copper compound solutions called leachate solutions. The metal (copper) could then be processed/extracted by electrolysis or a displacement reaction with a more reactive metal (e.g. scrap iron)
What are life cycle assessments used for?
to asses the environmental impact of products in each of the stages
What are the stages of LCAs?
- extracting and processing of raw materials
- manufacturing and packaging
- use and operation (during its lifetime)
- disposal at the end of its useful life (including transport and distribution)
What is a disadvantage of quarrying/mining?
- damaging appearance the landscape
- loud and noisy
- loss of habitats
How can metals be recycled?
by melting and recasting or reforming into different products
How are glass products sorted?
according to their colour and chemical composition
What are the stages of recycling glass?
- sorting
- crushing
- melting
What is corrosion?
The destruction of materials by chemical reactions with substances in the environment
e.g. rusting (both air and water needed for iron to rust)
How can corrosion be avoided?
by applying a coating that acts as a barrier, such as greasing, painting or electroplating.
- Some coatings are reactive and contain a more reactive metal to provide sacrificial protection
e.g zinc is used to galvanise iron
Give examples of alloys
-bronze (copper and tin)
-brass (copper and zinc)
-stainless steel (iron,carbon,chromium…)
What is a key feature of aluminium and its use?
low density which makes it suitable for manufacturing planes/ armour plating for military vehicles
Describe the difference between high carbon steel and low carbon steel
-
high carbon steel is strong but brittle
• uses: making tools and blades -
low carbon steel is softer and more easily shaped
• uses: car bodies
What is a key feature of stainless steel and what is it used for?
It is strong and resistant to corrosion
(used for utensils and cutlery)
What are ceramics?
inorganic, non-metallic solids fired in an oven
Give examples of ceramics
- pottery
- bricks
- soda-lime glass
- borosilicate glass
How are composites made?
By embedding a material known as the reinforcement into the matrix
Define reinforcement and matrix
reinforcement: fibres of fragments
matrix: material that surrounds the reinforcement and acts as a binder
Examples of matrix and reinforcement
carbon fibre
-matrix: polymer
-reinforcement: carbon fibres/nanotubes
Concrete
-matrix: cement
-reinforcement: sand and gravel
Fibreglass
-matrix: polymer
-reinforcement; glass fibres
What is meant by the terms ‘thermosetting’ and ‘thermosoftening’?
thermosetting (do not melt when heated)
- there are cross links between polymer chains
• hard
• rigid
thermosoftening (melt when heated)
- there are no cross links between polymer chains
What type of glass do we use most of the time?
soda-lime glass
What is the name of the glass with a higher melting point than soda-lime glass?
borosilicate
What is the Haber process?
The most important industrial chemical reaction which produces ammonia
What are the steps involved in the haber process?
- collect and purify nitrogen & hydrogen gases
- pass over an iron catalyst
- condensation of the ammonia which is then removed from the condenser once it is liquid
- recycling unused hydrogen and nitrogen
What are the conditions used in the Haber process?
- 200 pa
- 450oC
What is the forward reaction of the Haber process and how does this effect the conditions?
forward reaction = exothermic
- an increase in temperature shifts the equilibrium towards the reactants(more ammonia is produced)
- so there is a trade-off between increasing the rate of reaction by increasing the temp and reducing the yield
- There are fewer molecules of product than reactant which means an increase of pressure moves the equilibrium towards the products
- increasing the pressure increases the rate of reaction but high pressures are expensive and can be hazardous so 200 atm provides a compromise between ammonia production vs safety and cost
Where are the nitrogen and hydrogen from?
• nitrogen- the air
• hydrogen- made from hydrocarbons and natural gas
How does the Haber process work?
- The reactant gases are passed over an iron catalyst
- unused nitrogen and hydrogen are recycled
- the ammonia produced can then be used to make ammonium nitrate (a very nitrogen-rich fertiliser)
Explain the trade-off between increasing the rate and maximising the yield
• 450 degrees is a compromise between maximum yield and speed of reaction
• 200 atmospheres - highest pressure without making the process too expensive or dangerous
• iron catalyst- speeds up the rate of reaction
What is a fertiliser?
a substance that is applied to soil in order to supply plants with nutrients
What are the three main essential elements in fertilisers?
- nitrogen
- phosphorus
- potassium
What are advantages of formulated fertilisers?
- not as complex to use
- odourless
- better availability
- can be customised to tailor to different scenarios (needs of different plants)
What can ammonia react with to form nitric acids?
oxygen and water
What does the reaction between ammonia and nitric acid produce?
ammonium nitrate- ideal as it contains to sources of nitrogen
How are phosphate and potassium obtained?
- potassium chloride and potassium sulphate can be mined
- phosphate rock (insoluble solid) can be mined and then reacted with a number of acids to produce soluble phosphates
- nitric acid- phosphoric acid and calcium nitrate
- sulfuric acid- calcium sulphate and calcium phosphate (single superphosphate)
- phosphoric acid- calcium phosphate (triple superphosphate)
What are the two main soluble sources of potassium that can be used in fertilisers?
- potassium sulfate
- potassium chloride
