chemicals of the natural environment Flashcards
what is the hydrosphere?
made up of water and dissolved compounds
what is the lithosphere?
rigid outer layer of Earth, made up of crust and part of mantle below it
consists of mixture of minerals + abundance of elements
what are example of elements?
nitrogen
oxygen
argon
what are examples of compounds?
carbon dioxide
water vapour
what do the chemicals that make up the atmosphere consist of?
non metal elements
molecular compounds made from non metal elements
what are the structures of molecules?
- gases have small mol with weak forces of attraction
- only small amounts of energy needed to break forces
what are covalent bonds?
atoms within molecules are connected by covalent bonds
what happens in a covalent bond?
- electrons shared between atoms
- electrostatic attraction created between positive nucleus and shared pair of negative electrons
what are the 3 most abundant elements?
- oxygen
- silicone
- aluminium
what are both diamond and graphite?
minerals formed from pure carbon found in lithosphere
explain the diamond structure?
each carbon atom is covalently bonded to 4 other carbon atoms so hard
explain the graphite structure?
each carbon is covalently bonded to 3 other carbon atoms, arranged in sheets that can slide easily so soft
can conduct electricity bc spare electrons move between layers of atoms
what happens in both graphite and diamond
covalent bonds strong so both have high melting points + insoluble in water
what properties does silicone dioxide have?
- hard
- high melting point
- electrical insulator
- insoluble in water
what is silicone dioxide?
silicone and oxygen in lithosphere as compound silicone dioxde
forms a giant covalent structure
why is seawater in hydrosphere salty?
contains dissolved iconic compounds called salts
what are the properties of ionic compounds?
- high melting points bc ions held together by strong forces of attraction in a lattice
- don’t conduct electricity when solid bc ions are fixed in place
- conduct electricity when molten bc ions free to move
- dissolve in water bc water molecules are polar
what are the uses of metals?
- titanium
- aluminium
- iron
- copper
- titanium, strong, submarines
- aluminium, malleable, drink cans
- iron, high melting point, sauce pans
- copper, conductor, cables
what are metals?
giant structure of ions held together by strong force of attraction called metallic bond
what are the properties of metals?
- strong:
ions closely packed in a lattice structure - high melting point:
energy needed to break metallic bonds - malleable:
beaten into any shape as layers of metal ions can slide past each other - conductors of electricity:
electrons free to move through structure
what is the life cycle assessment?
helps scientists to make decisions about which method of extraction causes least environmental damage
what is the environmental impact of the following processes?
1) mining
2) processing
3) manufacturing metal products
4) transport to shops
5) running the product
6) reuse
7) recycle
8) throw away
1) - rocks wasted
- scar on landscape
- air pollution
2) - energy usage
- pollutants
3) - energy usage
4) - pollutants
5) - energy usage
6) - no impact
7) - less energy than initial manufacturing
8) - landfill sites remove wildlife habitats
how is aluminium extracted from its ore by electrolysis?
1) (a) ore purified to leave (a) oxide
2) (a) oxide mixed with cryolite to lower mp
3) mixture melted so ions move
4) current passes, positively charged (a) ions move towards n electrode
5) (a) formed at n electrode
6) negatively charged oxide ions move towards p electrode
7) oxygen formed at p electrode
at n electrode, what is the equation when (a) ions gain electrons to become neutral atoms?
Al3+ + 3e- —> Al
at p electrode, what is the equation when oxygen ions lose electrons to become neutral atoms?
2O2- + 4e- —> O2
what is electrolysis?
breaking down of an electrolyte using electric current
used to extract reactive metals from ores bc too reactive to be extracted by heating with carbon
when do ionic compounds conduct electricity?
- when molten
- when dissolved in solution
bc ions free to move through liquid
what happens when an ionic compound melts?
electrostatic forces between charged ions in crystal lattice are broken and ions free to move
what happens when a direct current is passed through a molten ionic compound?
- p charged ions attracted towards n electrode
- n charged ions attracted towards p electrode
what happens when ions get to the oppositely charged electrode?
they’re discharged (lose their charge)
eg:
electrolysis of molten lead bromide the non metal ion loses electrons to the p electrode to form bromide atom. bromine atom then bonds with a second atom to form a bromine molecule
how can the reactions at the electrodes be written as?
half equations meaning you write sep equations
2Br- —> Br2 + 2e-
lead ions gain electrodes from n electrode to form a lead atom:
Pb2+ + 2e- —-> Pb
this process completes circuit as electrons exchanged at the electrodes
what is the RFM?
tells total mass of atoms in a compound
eg:
- co2 = 12 + 16 + 16 = 44
add the top numbers together
what are ores?
rocks containing varying amounts of minerals from which metals can be extracted
large ores need to be mined in order to recover small % of valuable minerals eg copper
how can metals that are less reactive than carbon be extracted from their oxides by heating carbon?
- metal oxide reduced, lost oxygen
- carbon oxidised as gained oxygen
eg:
zinc can be extracted from zinc oxide by heating it with carbon:
zinc oxide + carbon —> zinc + carbon dioxide
how do you calculate a metals mass?
1) write formula
2) work out RFM
3) work out % mass of metal
4) work out mass of metal
what is an example of calculating a metals mass?
mass of zinc from 100g of ZnO
1) ZnO
2) RFM - 65+16= 81
3) RAM/RFM x 100 = 65/81 x 100 = 80%
4) in 100g, 80/100 x 100 = 80g
