Using Resources Flashcards
What is potable water
Water that is safe to drink
Methods of water treatment
- Filtration
- Sterilisation -> chlorine, UV, or ozone
2 methods of desalination (removal of salt from water)
- Distillation -> sea water is heated until it boils, and the steam is pure water, the steam is cooled and condensed to make potable water. Costs energy to boil water.
- Reverse Osmosis -> water is passed through a semi-permeable membrane at high pressure. Costs energy to create this high pressure. Cheaper than distillation.
Waste water treatment
- Waste water flows in sewers
- Screening and grit removal removes large solids from waste water
- Primary sedementation tanks - organic waste sinks to the bottom as sludge. Remaining water (effluent) is taken from the top)
- in Aeration tanks (air is pumped through), good bacteria kill harmful bacteria
- In final setting tanks, good bacteria sink to the bottom as sludge. Treated water returns to environment.
- Sludge gets anaeorobically digested by bacteria, producing methane
- Methane is burned for heat and electricity generation
Alternative ways of extracting metals
Phytomining: uses plants to absorb metal compounds through roots in soil containing such compounds. These plants are burned and the ash produced contains metal compounds. This ash is dissolved in acid to form a solution containing copper compounds. Better for environment - less digging etc
Bioleaching: uses bacteria to produce soluble metal compounds from insoluble metal compounds. Uses low-grade metal ores near to surface
Leaching - uses dilute acid to produce soluble metal compounds from insoluble metal compounds. Uses low-grade metal ores near to surface
- The products of these 2 different methods leads to metal compounds being dissolved in water and either via electrolysis or a displacement reaction the pure metal is obtained.
Life Cycle Assessment
The impact of a product on the environment throughout its life
- the 4 stages of the cycle:
Raw Materials
- using up limited resources such as ores
and crude oil damaging habitats through
quarrying, mining, or felling trees
Manufacture
- using up land for factories
- the use of machines and people
Usage
- The impact of a product on the environment during its use depends on the type of product
Disposal
- using up land for landfill sites
- whether any or all of the product can be
recycled or reused
What is corrosion
Oxidisation of a metal
Rusting
When iron or steel reacts with oxygen and water
Preventing corrosion
- sacrificial protection -> iron can be protected from rusting if it is in contact with a more reactive metal, such as zinc (galvanising)
- galvanising -> when iron is coated in zinc, stops oxygen and water reaching the iron
- painting, greasing
Uses of alloys
Gold: jewellery
Bronze (copper and tin)
Brass (copper and zinc)
Examples of composites
Carbon fibre and fibreglass (both very hard but brittle)
Ceramics
Soda-lime glass: made by heating sand, sodium carbonate and sandstone
Borosilicate glass: made from sand and boron trioxide -> higher melting point than soda lime
Haber process conditions
- iron catalyst
- high temps (450*C)
- high pressure (200atm)
Reactants of the Haber process
Nitrogen (from the air) and hydrogen (from methane/natural gas)
Stages of the Haber process
Stage 1: H2 and N2 gases are pumped into the compressor through pipes
Stage 2: The gases are compressed and heated
Stage 3: Some of the hydrogen and nitrogen react to form ammonia
Stage 4: Unreacted H2 and N2 and product ammonia pass into a cooling tank -> the ammonia is condensed and removed to pressurised storage vessels
Stage 5: The unreacted H2 and N2 gases are recycled back into the system
Equation for the reversible reaction in the Haber Process
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
Why is 450*C chosen
It is a compromise between having a lower yield of products but having a quicker rate of reaction
Why is 200atm chosen
It is a compromise between a lower yield of products but being made safely and economically -> increases rate
Function of a catalyst in the Haber process
Doesn’t affect the position of equilibrium but lowers the activation energy
-> without it the process would require higher temperatures to work
What are NPK fertilisers
- Water soluble compounds of nitrogen, phosphorus and potassium
- used to help crops grow and increase their yield
Phosphate rock
Is used as a raw material but not as a direct fertiliser as it is insoluble in water
BUT soluble salts can be made when it reacts with acids
Use of ammonia in making fertilisers
The salt it produces contains the ammonium ion, NH4+, which is a component of several fertilisers
- Ammonia also undergoes oxidation to produce nitric acid which is used as the source of the nitrate ion (another important ion found in fertilisers)
- Ammonium nitrate, a fertiliser and one of the most important ammonium salts, is made by reacting ammonia with nitric acid
Triple superphosphate fertiliser
Made from the reaction of phosphate rock with phosphoric acid (which is made from phosphate rock with nitric acid -> which is made from ammonia)
Disadvantages of fertilisers
- eutrophication
- salts are water soluble -> end up in water systems
- nutrients promote growth of algae
- the algae use up dissolved O2 -> causing fish to die
What salts are in single superphosphate
Calcium phosphate
Calcium sulfate
What salt is in triple superphosphate
Calcium phosphate
Sustainable development
Using resources to meet the needs of people today without preventing people in the future doing so
How are clay ceramics made
They are made by shaping wet clay and then heating it to a high temperature in a furnace -> which causes crystals to form and join together
Examples of clay ceramics
- china
- brick
- porcelain
How are ceramics made hard and waterproof
are often coated with a glaze, which hardens on heating
What components make up composite materials
-the reinforcement
-the matrix, which binds the reinforcement together
Fibre glass and carbon fibre reinforced polymer (CFRP)
- The fibres in these composite materials have a low density
- They are strong in tension so they are not easily stretched, but they are flexible
- The polymer resin which binds the fibres together is not strong but it is stiff
- The composite materials show a combination of these properties - they are strong, stiff and lightweight.
Wood vs Chipboard
- Wood itself is a natural composite material -> It consists of a reinforcement
of cellulose fibres bonded together by a matrix of lignin - The fibres are aligned alongside each other, so wood is stronger in one direction than it is in the other
- Chipboard contains randomly arranged wood chips bonded together by a glue, so it is strong in all directions.
How to produce potable water
- choose an appropriate water source of fresh water
- passing the water through filter beds
- sterilising
Bioleaching
Uses bacteria to produce leachate solutions that contain metal compounds
-> the metal compounds can be processed to obtain the metal through electrolysis or displacement with scrap metal
Phytomining
- Uses plants to absorb metal compounds
- the plants are harvested and then burned to produce ash that contains metal compounds
- the ash is then processed by electrolysis or displacement with scrap metal
Why is bioleaching and phytomining good
Avoid digging, moving and disposing of large amounts of rock used in traditional mining methods
What is the haber processed used to make
Ammonia which can be used to produce nitrogen based fertilisers
Phosphate rock reactions
Nitric acid: calcium nitrate and phosphoric acid
Sulfuric acid: calcium sulfate and calcium phosphate (single superphosphate)
Phosphoric acid: triple superphosphate (calcium dihydrogen phosphate)
