chemicals of the natural environment

Question 1

what is the hydrosphere?

Answer 1

made up of water and dissolved compounds

Question 2

what is the lithosphere?

Answer 2

rigid outer layer of Earth, made up of crust and part of mantle below it

consists of mixture of minerals + abundance of elements

Question 3

what are example of elements?

Answer 3

nitrogen
oxygen
argon

Question 4

what are examples of compounds?

Answer 4

carbon dioxide

water vapour

Question 5

what do the chemicals that make up the atmosphere consist of?

Answer 5

non metal elements

molecular compounds made from non metal elements

Question 6

what are the structures of molecules?

Answer 6

• gases have small mol with weak forces of attraction

- only small amounts of energy needed to break forces

Question 7

what are covalent bonds?

Answer 7

atoms within molecules are connected by covalent bonds

Question 8

what happens in a covalent bond?

Answer 8

• electrons shared between atoms

- electrostatic attraction created between positive nucleus and shared pair of negative electrons

Question 9

what are the 3 most abundant elements?

Answer 9

• oxygen
• silicone
• aluminium

Question 10

what are both diamond and graphite?

Answer 10

minerals formed from pure carbon found in lithosphere

Question 11

explain the diamond structure?

Answer 11

each carbon atom is covalently bonded to 4 other carbon atoms so hard

Question 12

explain the graphite structure?

Answer 12

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

Question 13

what happens in both graphite and diamond

Answer 13

covalent bonds strong so both have high melting points + insoluble in water

Question 14

what properties does silicone dioxide have?

Answer 14

• hard
• high melting point
• electrical insulator
• insoluble in water

Question 15

what is silicone dioxide?

Answer 15

silicone and oxygen in lithosphere as compound silicone dioxde

forms a giant covalent structure

Question 16

why is seawater in hydrosphere salty?

Answer 16

contains dissolved iconic compounds called salts

Question 17

what are the properties of ionic compounds?

Answer 17

• 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

Question 18

what are the uses of metals?

• titanium
• aluminium
• iron
• copper

Answer 18

• titanium, strong, submarines
• aluminium, malleable, drink cans
• iron, high melting point, sauce pans
• copper, conductor, cables

Question 19

what are metals?

Answer 19

giant structure of ions held together by strong force of attraction called metallic bond

Question 20

what are the properties of metals?

Answer 20

• 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

Question 21

what is the life cycle assessment?

Answer 21

helps scientists to make decisions about which method of extraction causes least environmental damage

Question 22

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

Answer 22

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

Question 23

how is aluminium extracted from its ore by electrolysis?

Answer 23

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

Question 24

at n electrode, what is the equation when (a) ions gain electrons to become neutral atoms?

Answer 24

Al3+ + 3e- —> Al

Question 25

at p electrode, what is the equation when oxygen ions lose electrons to become neutral atoms?

Answer 25

2O2- + 4e- ---> O2

Question 26

what is electrolysis?

Answer 26

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

Question 27

when do ionic compounds conduct electricity?

Answer 27

- when molten - when dissolved in solution bc ions free to move through liquid

Question 28

what happens when an ionic compound melts?

Answer 28

electrostatic forces between charged ions in crystal lattice are broken and ions free to move

Question 29

what happens when a direct current is passed through a molten ionic compound?

Answer 29

- p charged ions attracted towards n electrode | - n charged ions attracted towards p electrode

Question 30

what happens when ions get to the oppositely charged electrode?

Answer 30

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

Question 31

how can the reactions at the electrodes be written as?

Answer 31

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

Question 32

what is the RFM?

Answer 32

tells total mass of atoms in a compound | eg: - co2 = 12 + 16 + 16 = 44 add the top numbers together

Question 33

what are ores?

Answer 33

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

Question 34

how can metals that are less reactive than carbon be extracted from their oxides by heating carbon?

Answer 34

- 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

Question 35

how do you calculate a metals mass?

Answer 35

1) write formula 2) work out RFM 3) work out % mass of metal 4) work out mass of metal

Question 36

what is an example of calculating a metals mass?

Answer 36

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