Flashcards
Materials
Flashcards do conjunto (30)
- 1electrolytic cell- converts electrical energy into chemical energy
- has an external power supply since reactions don't occur naturally/spontaneously
- electrons flow from anode to cathode
- anode = positive electrode that attracts anions
- cathode = negative electrode that attracts cations - 2operation of electrolytic cell- anions in electrolyte flow to surface of anode where they're oxidised
- cations in electrolyte flow to surface of cathode where they're reduced - 3electrolysis of water2H2O + 2e- --> H2 + 2OH-
2H2O --> O2 + 4e- + 4H+
- unreactive salt is added to increase electrical conductivity of electrolyte since water is a poor conductor - 4metal production1. extraction
- mineral ores are extracted from Earth's crust
2. concentration
- mineral conc is increased by removing impurities
3. conversion
- minerals are converted to a metal compound that can undergo reduction
4. reduction
- pure metal is isolated from compound using electricity/reducing agent
5. refining
- minor impurities are removed by electrolysis to increase % purity of metal - 5stages of zinc production1. zinc mineral is extracted from Earth's crust + crushed to increase SA:V
2. conc. is increased by froth flotation
3. ZnS is converted to zinc sulfate via roasting (@ high temp.) + then reaction w sulfuric acid
4. zinc metal is obtained from electrolytic reduction of ZnSO4 solution - 6froth flotation- collectors (reagents) selectively absorb to ZnS particles + air bubbles in froth flotation cell
- hydrophilic component adsorbs to ZnS particles
- hydrophobic component adsorbs to air bubbles which carry collector + ZnS particles to surface of flotation cell - 7ZnSO4 electrolytic reduction half-equationscathode = Zn2+ + 2e- --> Zn
anode = 2H2O --> O2 + 4H+ + 4e-
(SO4 is stable so water reacts instead) - 8stages of aluminium production1. mineral ore is extracted from Earth's crust + crushed to increase SA:V
2. reacts to form sodium aluminate
3. sodium aluminate is converted to alumina
4. electrolytic reduction produces aluminium metal - 9aluminium electrolytic half-equationscathode = Al3+ + 3e- --> Al
anode = 2O2- --> O2 + 4e- - 10metals- elements that lose one or more electrons in a chemical reaction
- most reactive metals = readily lose valence electrons
- found in combined form since they lose electrons + form compounds w other elements
- least reactive metals = rarely lose valence electrons
- uncombined form since they don't lose electrons that enable them to form compounds - 11methods of reduction- dependent on position of metal on metal reactivity series
- Al and above are molten since very reactive (makes it harder to reduce so water is reduced instead)
- Zn and below are reduced in salt solution since less reactive - 12reduction of solid oxide by reducing agentreducing agent = substance used to reduce metals from combined form by removing oxygen or transferring 1 or more electrons
- advantage = reducing agents are abundant + inexpensive
- disadvantage = occurs at high temp which requires heat derived from combustion of fossil fuels - 13reduction of an aqueous salt solution by electrolysise.g., used in zinc production
- advantage = electrolysis is reliable
- disadvantage = high quantity of energy required from combustion of fossil fuels - 14reduction of a molten salt/oxide by electrolysis- water is reduced in preference to metal of interest since highly reactive metals are harder to reduce
- to address this, water is removed and they're in molten form instead
- advantage = electrolysis is reliable
- disadvantage = high quantity of energy is required which is derived from combustion of fossil fuels - 15addition polymerisation- monomers w C=C combine
- no loss of atoms - 16condensation polymerisation- monomers w different functional group combine
- loss of nH2O
- polyester = diol and dicarboxylic acid
- polyamide = amino carboxylic acid - 17advantages of synthetic polymers- highly versatile + suit a range of applications
- properties can be manipulated to increase applications
- relatively inexpensive to produce - 18disadvantages of synthetic polymers- monomers are derived from petrol which is non-renewable
- addition polymers aren't biodegradable
- can accumulate in aquatic ecosystems + harm wildlife if incorrectly disposed of - 19secondary interactions between polymer molecules- large + highly polarisable electron clouds which form dispersion forces
+ larger polymers = stronger DF = greater rigidity, elasticity, + melting point
- polymers w no funcional groups only have DF = inelastic, flexible, + low melting point
- polymers w polar functional groups have stronger secondary interactions (dipole-dipole + H bonds) = increases rigidity, elasticity, + melting point - 20cross-links- covalent bonds between polymer molecules in chain
- can be formed in manufacture or be introduced by cross-linking agents (e.g., sulfur)
- greatly increases elasticity, rigidity, + melting point
- polymers w cross-links usually don't melt when heated which makes them suitable for high temp applications - 21thermoplastic polymers- low melting point
- polymer molecules separate + flow past one another when heated
- can be reshaped repeatedly due to weak secondary interactions
- could be methyl/ethyl branched structure (disordered structure w weaker DF)
- can be recycled - 22thermoset polymers- high melting point
- cannot be reshaped when heated
- cross-linked, which prevents softening when heated + recycling - 23advantages/disadvantages of making polymers from non-renewable materials/fossil resourcesadvantages:
- fossil fuels are abundant + accessible
- manufacturing and recycling facilities are well-established
disadvantages:
- non-renewable source
- cost of petrol is increasing
- aren't biodegradable - 24advantages/disadvantages of making polymers from renewable materialsadvantages:
- renewable sources are biodegradable
- raw materials are relatively inexpensive
- can be prepared from recycled materials/unused wood
- decomposition by hydrolysis doesn't produce toxic by-products
disadvantages:
- growing crops reduces land availability
- requires fertilisers + pesticides which are derived from fossil fuels
- hydrolysis only occurs under certain conditions - 25advantages + disadvantages of biodegradable polymersadvantages:
- reduces amount of waste accumulating in landfill
- raw materials are abundant
- decompose over short period of time + can be used as fertiliser
disadvantages:
- limited number of synthetic polymers are biodegradable
- greenhouse gases are released in decomposition
- O2 and H2O must be present for natural decomposition - 26advantages of recycling polymers- conserves finite resources like petrol
- reduces greenhouse gas emissions from production
- reduces landfill which releases methane
- reduces amount of plastic damaging ecosystem
- reduces atmospheric pollution caused by incineration of plastic waste - 27advantages of recycling metals- conserves finite resources used in their production
- reduces mining which is expensive, creates waste, and is a source of atmospheric pollution
- reduces quantity of waste produced during metal production
- reduces amount of metals in landfill - 28recycling of thermoplastic + thermoset polymersthermoplastic = melted + reshaped into new products
thermoset = ground/shredded for use as filling or insulating materials - 29advantages of using composite materials- improved properties that weren't present in individual components
- can be designed for a specific use
- can be moulded into particular shape which increases range of applications - 30recycling composites- not easily recyclable because they contain a thermoset polymer matrix
- mechanical grinding can grind the composite material into smaller particles that are used as a filler
- pyrolysis involves heating composite in O2 to combust thermoset polymer matrix + retain reinforcement fibres
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- Descrição
- South Australian Certificate of Education Chemistry FlashCards sobre Materials, criado por Michala Baldwin em 31-10-2022.
- Criado por
- Michala Baldwin · out 2022
- Atualizado
- 31 out 2022
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