C6 Flashcards
what is a metal ore?
a rock which contains enough metal to make it economical to extract the metal
how can a metal be extracted from it’s ore?
by reduction (using carbon) or by electrolysis (splitting with electricity)
what do some ores may have to be before metal is extracted?
concentrated- getting rid of unwanted rocky material
what are two other ways to extract metals from their ores?
-biological methods
-displacement reactions
when an ore is reduced what happens?
oxygen in removed from it
how does the position of the metal in the reactivity series effect reduction?
it determines whether it can be reduced with carbon
metals higher than carbon in the reactivity series…
can be extracted using electrolysis
metals below carbon in the reactivity series
can be extracted by reduction using carbon
what is the reactivity series order?
potassium
sodium
calcium
magnesium
aluminium
carbon
zinc
iron
tin
lead
hydrogen
copper
silver
gold
platinum
what is reduction?
removal of oxygen from a compound
what is displacement?
a reaction where a more reactive metal removes a less reactive metal from it’s compound
what state does a metal have to be in before it is extracted using electrolysis?
it has to be molten
what is the main difference in electrolysis and reduction with carbon?
electrolysis is expensive as it uses electricity
what is smelting?
an ore being heated in a furnace
what are two pure unreactive metals?
silver and gold
why is it better to extract copper using electrolysis?
smelting produces copper which is impure- it won’t conduct electricity.
copper is often used in electrical wiring- which makes it not useful.
electrolysis is used to purify it even if it is expensive.
what are low grade ores?
ores that only contain a small amount of metal in them
what are two biological methods of extraction?
bioleaching
phytoextraction
what is bioleaching?
use of bacteria to separate metals from their ores. the bacteria get energy from the bonds between the atoms in the ore which separate the metal from the ore.
what is phytoextraction?
growing plants in soil that contains metal compounds. the plants cant use or get rid of the metals so they gradually build up in the leaves. the plants are then harvested, dried and burned in a furnace
the only problem with this is that plants take a while to grow
what is a life cycle assessment?
an assessment that looks at each stage of the life of a product- it shows the potential environmental impact at each stage
what is in a life cycle assessment?
-use of sustainable raw materials
-use of energy at all stages
-use of water at all stages
-production and disposal
what could you consider when choosing raw materials?
-metals have to be mined and extracted from their ores- needs lots of energy which causes pollution
-raw materials for chemical manufacture often come from crude oil:
- finite resource
- getting crude oil and refining requires a lot of energy and causes pollution
what should you consider when assessing manufacture of a product?
-use of energy
-pollution (harmful gases)
-waste products and how to dispose of them
-use of water in chemical manufacture and water pollution
what can some waste be turned into?
other useful chemicals which reduces the amount that ends up polluting the environment
what can you consider when assessing product use?
-if gives off toxic fumes
-fertilisers can leak into water sources and cause damage to eco systems
-burning fuels releases greenhouse gases
what should you consider when assessing disposal of a product?
-landfill waste can pollute water and land and products in landfill may be burnt which causes air pollution
what does burning fossil fuels cause?
acid range and climate change
why is recycling a good option?
-recycled materials use little energy needed to extract and refine the material
-it saves money
-recycling cuts down on waste sent to landfill- decreases pollution
why might recycling be complex?
-you need energy to reprocess the materials into new forms
-items will often need sorting into different catagories
-you need to compare how much energy is used for recycling vs disposing
what is crude oil formed from?
buried remains of plants and animals
what is a hydrocarbon?
a compound that contains carbon and hydrogen only
what is viscosity?
how thick a substance is
what is flamability?
ability to ignite something
what is crude oil mostly used for?
used as a raw material to create lots of petrochemicals- petrol or natural gas
what is crude oil a mixture of?
lots of different length hydrocarbons
how are the different compounds in crude oil separated?
by fractional distillation
what is the process of fractional distillation using crude oil?
-crude oil is heated until most of it has turned into a gas
-the gas enters the fractionating column
-the hydrocarbons at the bottom have a high boiling point and they turn back into liquids and drain out the collumn at the bottom
-the shorter hydrocarbons at the top of the column have lower boiling points and they turn into a liquid and drain out at the top of the column where it is cooler.
where is it hot and where is it cold in a fractionating column?
cold at the top
hot at the bottom
short hydrocarbon top
long hydrocarbons bottom
what is the order of the hydrocarbons in a fractionating column from top to bottom?
-LPG (liquefied petroleum gas)
-petrol
-naptha
-kerosene
-diesel
-oil
what is petrol used for?
cars
what is naptha used for?
used in chemical production
what is kerosene used for?
airplane jet fuel
what is diesel used for?
diesel engines