C6.1 Flashcards
What is an ore?
- A rock or mineral containing enough metal to make it economical to extract the metal
What are 4 ways metals can be extracted from their compounds?
- Reduction
- Electrolysis
- Biological methods
- Displacement reactions
How is iron extracted from its compound?
- Iron ore is heated with carbon in a blast furnace
- Iron (III) oxide is reduced to molten iron
How is aluminium extracted?
- Heating aluminium oxide (Al2O3) until it reaches the liquid state would be very expensive, so it is dissolved in molten cryolite, which reduces its melting point, as it itself has a much lower melting point than aluminium
- It is electrolysed in a cell encased with steel
- Its electrodes are made of graphite
- The sides of the cell are the cathode, and graphite blocks at the top of the cell are the anodes
- Aluminium is produced at the cathode
- Oxygen is produced at the anodes, and reacts with them to produce carbon dioxide, so they need to be replaced frequently
What is bioleaching?
- Bacteria break down metal ores and produce an acidic solution containing metal ions
- This solution is called the leachate
- The leachate can then be processed to produce the metal
What is phytoextraction?
- A crop is planted in soil containing a low-grade ore
- The plants absorb the metal ions through their roots
- They are harvested and burnt
- The ash has a high concentration of metal
- It is processed to produce the metal
Why are bioleaching and phytoextraction used, and what is their disadvantage?
- To extract metal from low-grade ores
- They are cheaper than traditional mining and processing
- They have a much smaller impact on the environment than mining
- Both processes are slow
What is the Contact Process? List its 3 stages.
- Process to make sulfuric acid
- Sulfur burns in the air to make sulfur dioxide:
S + O2 -> SO2 - 2SO2 + O2 -> 2SO3
- H2O + SO3 -> H2SO4
Which stage of the process is reversible? state the conditions chosen for it, and why they’re chosen.
- Stage 2
- A pressure of 2atm, as the position of equilibrium is already far to the right
- A temperature of 450°C as although the forward reaction is exothermic, the rate of reaction needs to be reasonable
- Vanadium (V) oxide catalyst (V2O5)
What is the Haber process?
- N2 + 3H2 -> 2NH3 (reversible)
What are the conditions used in the Haber process, and why were they chosen?
- 200 atm, which is a compromise as a higher pressure should increase the rate of reaction, but high pressures are expensive and dangerous to maintain
- 450°C as although the forward reaction is exothermic, the rate of reaction needs to be reasonable
- Iron catalyst
What else is done to make the production of ammonia efficient?
- Unused hydrogen and nitrogen are recycled
- The gases are cooled so ammonia condenses and leaves the reaction vessel
What are factors to consider when choosing an industrial process?
- Cost of raw materials
- Availability of raw materials
- Energy costs
- Rate
- Equilibrium position
What 3 of the essential elements needed by plants, and what does a lack of them cause?
- Nitrogen
- Phosphorus
- Potassium
- Poor growth and discoloured leaves
- A reduction in the quantity and yield of food
What are fertilisers?
- Substances that replace the elements used by plants
- They can only be used by plants if they’re in a water-soluble form
What are 2 fertilisers used in agriculture, and what are the raw materials some of them are they made from?
- Ammonium nitrate
- Ammonium sulfate
- Nitrogen: air
- Hydrogen: natural gas and water
- Sulfur
How is potassium sulfate made?
- Titration using potassium hydroxide, sulfuric acid and phenolphthalein
- When the titration has reached its end point, activated charcoal is added
- This attracts the phenolphthalein so they can be filtered out together
How is ammonium sulfate made?
- Titration using ammonia solution, sulfuric acid and methyl orange (red in acids and yellow when neutral)
- The amount of acid needed to reach the end point should be recorded so the process can be repeated without any indicator
What is a batch process, and what is a continuous process?
- Batch processes make products in limited amounts at different times
- Continuous processes make products in large amounts all the time, so tend to be used in industry
How are continuous processes different to batch processes?
- Their rate of production is higher
- They need fewer workers
- Shut-down periods are rare
- It is easy to automate the process
- The equipment needed is more expensive
What is an alloy?
- A mixture of 2 or more elements, at least one of which is a metal
What is steel made of, some of its properties, and some uses of it?
- Mainly iron, and some carbon
- It is harder and stronger than iron, but less likely to rust than it
- Buildings, bridges and cars
What is duralumin made of, some of its properties, and a use of it?
- Aluminium and copper
- Has a very low density, but is stronger than aluminium
- Aircraft parts
What is solder made of, some of its properties, and a use of it?
- Tin and lead
- It gradually solidifies as it cools down, and is a good conductor of electricity
- Joining components in electrical circuits as it can be worked easily
What is brass made of, one of its properties, and some uses of it?
- Copper and zinc
- It is harder than copper and zinc
- Musical instruments
What is bronze made of, some of its properties, and some uses of it?
- Copper and tin
- Harder and stronger than both metals, and more resistant to corrosion than both of them
- Bells and sculpture
What is corrosion?
- The reaction of a metal with substances in its surroundings, such as air and water
Give examples of corrosion, and what they’re caused by.
- Silver: hydrogen sulfide, oxygen and water
- Iron and steel: oxygen and water
- Metals like gold and platinum do not corrode at all
Describe the corrosion of iron.
- When iron and steel corrode it us known as rusting
- Iron + oxygen + water -> hydrated iron (III) oxide
- Hydrated iron oxide is orange-brown rust, which flakes off of the object, until more metal is exposed underneath, and this can continue until the entire object corrodes away
How can rusting be reduced?
Making a barrier between the iron and oxygen/ water.
- Painting
- Coating with oil, grease or plastic
- Plating with tin
- Galvanising
What is the problem with most methods of protecting iron from rusting?
- If the protective barrier is damaged, the iron is exposed to air and water
- If a less reactive metal than iron, such as tin, is used, it rusts even faster than normal when it becomes exposed to air and water
What is sacrificial protection? Give an example.
- Coating a metal with a more reactive metal, as the layer of metal acting as protection will be oxidised more easily, even if the metal underneath becomes exposed
- Galvanising is when iron is coated with a layer of zinc
What are ceramics, and what are some of their common properties?
- Hard, non-metallic materials
- Include: brick, china, porcelain and glass
- High melting points, hard and stiff yet brittle, poor conductors of electricity and heat
What are composite materials? Give 2 examples.
- Two or more materials combined together that have different properties
- One material (the reinforcement) is embedded in another material (the matrix/ binder)
- Fibreglass is made from fibres of glass in a polymer matrix
- It has a low density like the polymer, but is strong like glass
- Concrete is made from aggregate in cement, and has a high compressive strength
What is a life-cycle assessment, and what should it include?
- ‘Cradle to grave’ analysis of the impact of making, using and disposing of a manufactured product
- Use of raw materials and energy for production
- The transport of the product
- The product’s lifespan and if any of it can be recycled
- The disposal of the product, and how easily any of it can decompose
Why is recycling important?
- It conserves raw materials and energy
- Reduces the release of of harmful substances in the environment
- Reduces waste
Which aspects of recycling should be considered when deciding to recycle a material?
- How easy sorting it is
- If making it from raw materials requires less energy than recycling it
- If recycling or disposal is cheaper
- How many times it’s been recycled before, as this reduces the quality of the material
- The amount and type of by-products released
How are some materials recycled?
- Metals, glass and polymers are heated and moulded again
- Paper is mixed with water, cleaned, rolled and heated
