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chemistry > C10 (resources) > Flashcards

C10 (resources) Flashcards

1
Q

what do humans use resources for?

A
  • warmth
  • shelter
  • food
  • transport
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2
Q

give examples of resources produced by agriculture:

A
  • cotton, from a plant. modern agriculture allows us to grow enough to meet the needs of the planet
  • planting trees, which can be used for timber/fuels. e.g. many power stations run on bio-fuels such as wood chips
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3
Q

give an example of how we’ve replaced natural resources with a synthetic alternative:

A
  • rubber
  • natural rubber comes from the sap of a tree
  • synthetic rubber is produced using crude oil, and about 2/3 of the rubber used globally is synthetic
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4
Q

give examples of finite resources:

A
  • fossil fuels (we use millions of kilograms every day)
  • metal (huge amounts are extracted from the Earth’s crust)
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5
Q

what does it mean to be sustainable?

A

meeting our needs without preventing future generations from meeting theirs

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6
Q

how does chemistry play an important role in our use of resources?

A
  • artificial fertilisers allow us to grow more food with the land available
  • provides water that is safe to drink
  • processes such as phytomining and bioleaching help us to extract metals more efficiently
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7
Q

what does drinking water require in order to be safe for human consumption?

A
  • sufficiently low levels of dissolved salts (e.g. sodium chloride, magnesium, calcium ions)
  • cannot have high levels of microbes (e.g. bacteria)

water that is safe to drink is called potable water

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8
Q

what is the difference between potable and pure water?

A
  • pure water in the chemical sense contains no dissolved substances at all
  • potable water does, just in quite small amounts
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9
Q

where is most of our freshwater provided from in the UK?

A

rainwater, as it contains low levels of dissolved substances (dissolves gases as it falls through the air)
- this water collects in the ground in aquifers, and in lakes, rivers, and reservoirs
- it is freshwater, not potable water

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10
Q

how do we produce potable water?
DESCRIBE THE FILTRATION STAGE

A
  1. screening removes large solid particles i.e. grit by passing the water through filter beds
  2. sedimentation allows the small solid particles to sink to the bottom of the settlement tank, forming sewage sludge while the liquid (effluent) remains above
  3. adding aluminium sulfate clumps together the remaining solids so that they also sink to the bottom and all solids are removed
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11
Q

how do we produce potable water?
DESCRIBE THE CHEMICAL TREATMENT STAGE

A
  1. use chlorine and UV light to get rid of harmful bacteria/microbes
  2. test the water and balance the pH, which needs to be at pH 7 for safe consumption
  3. the water is stored in large tanks and is released into homes, businesses and factories
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12
Q

what do countries with no fresh water access do to get potable water?

A
  • in the UK we have a lot of fresh water access, with low levels of dissolved minerals
  • in many places, fresh water is scarce, and the only available water may be too salty and contain too many dissolved minerals to drink (e.g. sea water)
  • potable water is produced by desalination
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13
Q

what is desalination?

A

reduces the levels of dissolved minerals down to an acceptable level for potable water

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14
Q

describe reverse osmosis:

A

apply pressure to salt water to push it through a semi-permeable membrane, where the water gets through but the salt doesn’t

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15
Q

describe the method for distillation:

A
  • boil the water at 100 degrees celsius, so it vapourises
  • the vapour rises, and condenses into a separate chamber to the salt
  • the salt has a different boiling/melting point, so it doesn’t evaporate with it
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16
Q

describe some methods of desalination:

A
  • distillation
  • reverse osmosis, by passing the water through membranes
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17
Q

what are the disadvantages of the methods of desalination?

A

require very large amounts of energy, which is expensive
- not done here in the UK, but done in the Middle East with little access to freshwater. they have more money (from their oil), and more solar energy to power the process

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18
Q

what are the main human uses of water?

A
  • only a small percentage used for drinking
  • large amount of water is used for personal hygiene e.g. baths and showers
  • water is also used for flushing toilets and washing clothes
  • a lot of water is also used in agriculture
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19
Q

what is negative about waste water, and how can we fix it?

A
  • contains many organic molecules (e.g. urine, faeces). also contains harmful microorganisms (e.g. bacteria)
  • the water must be treated before being released back into the environment
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20
Q

describe the stages of waste water treatment:

A
  1. the sewage is screened by passing through a mesh, removing solids and pieces of grit
  2. the sewage can settle in large sedimentation tanks, producing a liquid effluent and a semi-solid sludge which sinks
  3. this sludge is taken away and digested by anaerobic bacteria, and this produces biogas which can be burned for electricity or as bio-fuels. the digested sludge forms sludge cakes can be used as fertilisers for farming
  4. the liquid effluent still contains organic molecules and harmful microorganisms. air is bubbled through the liquid, allowing aerobic bacteria to multiply, which digest the molecules and microorganisms
  5. the liquid effluent can be safely discharged into nearby rivers/the sea
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21
Q

what happens to water used in industry?

A
  • a lot of water is used in industry, e.g. in making paper and chemicals
  • when this water is treated, any harmful chemicals and organic matter must first be removed
  • after this, the water can then safely enter general sewage treatment
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22
Q

describe the method of producing potable water from groundwater aquifers:

A

this is usually safe to drink, once treated with chlorine
- however, aquifers can sometimes by polluted e.g. with fertilisers from farms, so the water from aquifers must be tested carefully

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23
Q

describe producing potable water directly from waste water (e.g. sewage):

A

this is only done in places where water is scarce, as it takes many purification steps

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24
Q

describe producing potable water from salt water:

A

must be desalinated. this requires a lot of energy and is expensive

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25
Q

how are most metals found in the Earth’s crust?

A

already reacted with other elements, e.g. oxygen

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26
Q

how is copper used?

A
  • very important
  • used in electronic equipment, e.g. phones, electrical wiring, plumbing pipes
  • however, it’s becoming scarce, as it’s a finite resource
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27
Q

how is copper typically extracted?

A
  • through mining, melting, and electrolysis
  • energy is required, the machinery is expensive
  • huge environmental impact on biodiversity, due to deforestation
  • CO2 emissions
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28
Q

what is a metal ore?

A

a compound that contains enough metal to make it economical (cost-effective) to extract the metal

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29
Q

what are low grade ores?

A

ores that contain a very small amount of the desired metal, meaning it’s harder to extract the metal economically from these ores

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30
Q

describe the method of phytomining:

A
  1. plants are grown on the land (e.g. industrial waste sites) containing the copper compound, usually in the form of low grade ores
  2. the plants’ roots absorb the copper compound, and concentrate it in their tissue, through translocation
  3. the plants are then harvested and burned. the copper from the leaves reacts with oxygen in the air to form a copper oxide, collect the ash
  4. react the ash with sulfuric acid to get copper sulfate
  5. electrolyse it, extract the copper
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31
Q

what are the pros and cons of phytomining?

A

pros:
- can obtain copper in areas with low grade copper ores
- better than deforestation of massive rainforests for mining (less air pollution)

cons:
- energy is required in electrolysis, costly
- expensive to obtain sulfuric acid
- burning the plants releases CO2
- slower process

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32
Q

describe the method of bioleaching:

A
  1. bacteria are mixed with the low grade ore
  2. the bacteria carry out chemical reactions and produce a solution called the leachate (a liquid that has passed through an organism), containing the metal compound we want
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33
Q

what are the pros and cons of bioleaching?

A

pros:
- cheap, as it’s simply
- environmentally friendly, unlike smelting (traditional mining) which produces carbon and sulfur
- can be used in low grade ores when high grade ores are limited in availability

cons:
- very slow process
- efficiency in which the bacteria converts the copper ore into a copper metal is very low, so lots of waste is produced

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34
Q

how could we extract copper from a copper ore/compound?

A
  • we can displace the copper using iron, as iron is more reactive than copper. we usually use scrap iron as it’s cheap
  • we can also extract the copper using electrolysis
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35
Q

what are the positives of phytomining and bioleaching?

A
  • allow us to economically extract metal from low grade ores. this is important as the resources of metal ores are limited
  • do not involve digging, transporting and disposing of large amounts of rock, unlike in traditional mining
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36
Q

what is a life-cycle assessment?

A

attempts to put a number on the environmental impact of a product

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37
Q

what are the 4 main stages when carrying out the life cycle assessment of a product?

A
  • assess the environmental impact of extracting and processing the raw materials
  • manufacturing the product and its packaging
  • using the product during its lifetime
  • disposing the product at the end of its life
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38
Q

describe stage 1 of the life cycle assessment:

A

all the raw materials we need come from the Earth’s crust, atmosphere, oceans, or living organisms. obtaining these materials has an impact on the environment, e.g.
- using up limited resources such as ores and crude oil
- damaging habitats through quarrying, mining, or felling trees

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39
Q

describe stage 2 of the life cycle assessment:

A

manufacturing can impact the environment, such as through:
- using up land for factories
- the use of machines and people

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40
Q

describe stage 3 of the life cycle assessment:

A

the impact of its use on the environment depends on the type of product. cars will have a big impact, a wooden chair will have less, unless it needs cleaning/repair
- a toy could require lots of batteries. the production of batteries produces a lot of toxic waste

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41
Q

describe stage 4 of the life cycle assessment:

A
  • using up land for landfill sites
  • whether any of the product can be recycled or reused
  • the harmful chemicals contained must be disposed of carefully, and this may require a lot of energy
  • it also takes energy to transport used products for disposal (e.g. to landfill/recycling centre)
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42
Q

describe the formation of plastics:

A
  • the oil must be extracted from the ground then transported to oil refineries
  • the hydrocarbons must be separated then cracked
  • the polymer must be produced
  • all of these processes take a lot of energy, which is generated by burning fossil fuels, leading to climate change
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43
Q

describe the extraction of metals:

A

the ore must be dug out of the mine and transported for processing. the metal must then be extracted from the ore and this can produce large amounts of toxic waste products

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44
Q

compare stage 1 and 2 of the life cycle assessments of a paper vs plastic bag:

A
  • plastic bags are produced using chemicals from crude oil. paper bags are made from wood from trees
  • crude oil is a non-renewable source. trees are renewable, as we can simply plant more
  • extracting crude oil can be harmful to habitats, e.g. an oil leak. felling trees for wood is also extremely destructive to habitats such as forests
  • both crude oil and wood must be chemically processed, requiring a large amount of energy and releasing waste products. making paper also requires a lot of water
45
Q

compare stage 3 and 4 of the life cycle assessments of a paper vs plastic bag:

A
  • plastic shopping bags are strong, and are often reused as bin liners. paper bags aren’t as strong, and tend to tear - they’re often used only once before being thrown away
  • both plastic and paper bags must be transported either to recycling centres or to landfills
  • paper bags are often heavier than plastic bags, requiring more energy to transport
  • plastic is non-biodegradable (not broken down by microorganisms), so remain in the environment for a long time, however, paper breaks down quickly, especially if it’s wet. plastic bags therefore are a major form of litter, and fill up landfills
46
Q

what are the issues with life cycle assessments?

A
  • we can measure the use of water, energy, and the production of waste products. we cannot always be certain of how damaging these are to the environment. in some cases, we must make estimates or value judgements, which aren’t always accurate
  • they can also be biased (e.g. to support claims by advertisers)
47
Q

what objects are formed from raw materials?

A
  • glass
  • metal
  • building materials
  • plastic
  • clay ceramics
48
Q

how are raw materials obtained?

A

through quarrying/mining, which is harmful to the environment
- quarrying produces a lot of dust, destroying habitats
- mining releases harmful chemicals into the environment
also takes a lot of energy to turn these raw materials into useful products, and this energy comes from limited resources, e.g. fossil fuels

49
Q

how can we reduce our need for raw materials/resources?

A

recycle/reuse products, saving energy and limited resources. also reduces the amount of waste produced and have a less harmful effect on the environment

50
Q

describe the slogan: ‘reduce, reuse, recycle’

A
  • helps to cut down on the amount of waste produced, and on the amount of products/services used
  • REDUCE the amount of waste produced
  • REUSE items as much as possible before replacing them, reducing the amount of new material required to be created
  • RECYCLE items wherever possible, so they don’t go to landfill and release toxic chemicals into the environment, and don’t product CO2 when burnt in an incinerator
51
Q

how can glass bottles be recycled/reused?

A
  • can be reused
  • can be crushed/melted to make different glass products, e.g. jars
  • reduces the space needed in landfills, as it takes up to 4,000 years to decompose
52
Q

what can plastic bottles be recycled into?

A

fleece jackets, carpet

53
Q

how do we recycle metals?

A

melt them and recast them into different products (e.g. ingots), however metals must be separated before being recycled, and that depends on the desired properties of the final product
- saves energy, as no mining/extraction is required, preserving precious natural resources like coal/iron ore
- the combustion of coal is also a contributor to climate change

54
Q

how can we promote recycling?

A
  • offer rewards: however, this simply promotes more consumption, as they don’t award you for reduced consumption
  • educate the community and schools about recycling and the environment
55
Q

what are the pros and cons of reducing our waste?

A

pros:
- reduces methane (waste decays anaerobically) from landfills
- requires less energy compared to creating new materials (less CO2 emissions, due to burning coal)

cons:
- difficult to quickly switch to a reduced, less luxurious lifestyle

56
Q

what are the pros and cons of reusing products?

A

pros:
- conserves valuable resources
- causes less pollution than making new products from new materials

cons:
- the quality of the product will decrease over several rounds of reuse

57
Q

what are the pros and cons of recycling products?

A

pros:
- less energy to recycle than to extract raw materials
- it gives the product a USP, meaning people are more willing to buy the product

cons:
- may reduce the quality of the finished product
- expensive and difficult process, as it must be sorted and processed

58
Q

define corrosion:

A

the destruction of materials by chemical reactions with substances in the environment

59
Q

why must we prevent corrosion?

A
  • so the material lasts longer
  • so it has structural stability
  • so it looks more aesthetically pleasing
  • to keep its electrical conductivity high
  • otherwise we’d be unable to recycle it
60
Q

describe rusting:

A

only applies to iron, and alloys of iron such as steel.

61
Q

how could you carry out an experiment on the conditions required for rusting?

A
  • 3 test tubes
    1. iron nail in distilled water, test tube is open to the air WATER AND AIR
    2. iron nail is also in distilled water, but the water is being boiled, removing any dissolved air. the water is covered in oil, preventing any air in the test tube from dissolving in the water WATER BUT NO AIR
    3. anhydrous calcium chloride powder, removing water from the air in the test tube. place a rubber bung on the test tube, preventing any moist air from entering AIR BUT NO WATER
  • leave these for several days, and look for changes
  • 1’s should be covered in rust. 2’s and 3’s nails should have no rust, as corrosion requires both air and water
62
Q

what is the problem with corrosion, and what are the solutions?

A
  • corrosion damages materials
  • artificial coating where we put something (grease/paint/coating the metal with another metal (electroplating)) on the outside of the metal so it doesn’t come into contact with hazards/oxygen, so it doesn’t damage/corrode
63
Q

describe electroplating:

A

aluminium is commonly used. the surface naturally reacts with oxygen in the air to form a thin layer aluminium oxide, protecting the metal underneath from any further corrosion
- this could be referred to as a natural layer of oxide coating

64
Q

what is sacrificial protection?

A
  • coating valuable things with less valuable elements
  • e.g. coating railings with zinc. it’s not structurally integral and can’t be used by itself as it’s too flexible.
  • if the zinc is scratched, it still prevents corrosion as it’s more reactive than the metal beneath, meaning it corrodes instead of the metal
65
Q

what does ductile mean?

A

it can be thread through wires

66
Q

what is galvanising?

A
  • coating a metal with zinc
  • e.g. iron nails covered with zinc are galvanised nails
67
Q

what is an alloy, and how is it made?

A

contains a metal blended with other elements. it’s a mixture
- melt the metal, mix in other elements, and allow the alloy to cool

68
Q

why are alloys harder than pure metals?

A
  • in pure metals, the atoms form layers. hammering the metal means the atoms slide over each other, making them relatively soft
  • the atoms in an alloy are different sizes, therefore disrupting the layers and stopping them from sliding, so they’re harder
69
Q

describe bronze:

A
  • an alloy of copper and tin
  • as it’s extremely hard and tends not to corrode, it’s used for statues
70
Q

describe brass:

A
  • alloy of copper and zinc
  • although it’s harder than pure copper, it can be formed into different shapes
  • it’s used for musical instruments and door handles
71
Q

describe gold as an alloy:

A
  • used in jewellery, but pure gold is too soft
  • usually gold is alloyed with silver, copper, and zinc to make it harder

it’s purity is rated in carats. 24 carats is 100% gold, whereas 18 carats is 75% gold

72
Q

describe steel:

A
  • alloys of iron containing non-specific amounts of the non-metal carbon
  • also contains other metals
  • high carbon steel is extremely hard and brittle. it tends to break if hit with a hammer. used to make cutting tools, such as chisels
  • low carbon steel is softer and more easily shaped. it is used to make car bodies
73
Q

what is a problem with steel?

A
  • an alloy of iron, meaning it can rust. carbon can also corrode easily, and must be protected from the water and air
  • to prevent that, as well as iron and carbon, stainless steel contains chromium and nickel
  • stainless steel is hard, and resistant to corrosion. nickel is corrosion resistant and chromium makes it shiny
74
Q

describe aluminium alloys:

A
  • low density
  • extremely useful, e.g. in plane fuselages
75
Q

describe soda-lime glass:

TYPE OF CERAMIC

A
  • most of the glass that we use
  • ideal for items such as windows and bottles
  • to make it, mix together sand, sodium carbonate and limestone. heat this in a furnace until it melts. when it cools, it solidifies into any shape we want
  • has a relatively low melting point, limiting its uses
76
Q

describe borosilicate glass:

TYPE OF CERAMIC

A
  • higher melting point than soda-lime glass
  • useful for objects that require heating, e.g. kitchenware and labware
  • made by melting a mixture of sand and boron trioxide
77
Q

describe clay ceramics:

TYPE OF CERAMIC

A
  • unlike glass, clay is a mineral found in the ground
  • when it’s wet, it can be shaped, and is then heated in a furnace to harden
78
Q

what is a ceramic, and how is it formed?

A

a material made out of clay soil, that has been dug out of the ground and heated in a kiln oven
- dig the clay out of the ground. shape it. bake it in a kiln oven

79
Q

what are composites?

A

most are made by combining two different materials. combines the two materials’ favourable qualities
- the reinforcement (consisting of fibres/fragments of one material)
- this reinforcement is then surrounded by a matrix or binder material

80
Q

describe a Macintosh jacket composite:

A

has a thin layer of cotton between two layers of rubber. therefore, it’s waterproof and warm

81
Q

describe the carbon fibre composite:

A

the reinforcement material is fibres of carbon, and the matrix is a plastic resin
- very strong and very light, making it extremely useful in cars/aircraft parts

82
Q

describe reinforced concrete (composite):

A
  • has steel bars surrounded by concrete
  • extremely strong, used to build buildings
83
Q

what do the properties of polymers depend on?

A

the monomer and the conditions used to make the polymer
- e.g. you can change the conditions but use the same monomer to make high density/low density polymers

84
Q

describe high and low density polymers:

A
  • high density polymers have more polymer strands per unit space. they’re more dense, and harder
  • low density polymers have branches which separate the strands, meaning they’re further away from each other. they’re less dense, and less hard
85
Q

how could we change the properties of a polymer through its formation conditions?

A
  • temperature
  • reaction pressure
  • catalyst
86
Q

what are thermosoftening polymers?

A
  • they melt when we heat them
  • we can then reshape them while they’re soft
  • they then go back to a solid once cooled back down
  • this is how a 3D printer works
87
Q

describe what happens to thermosoftening polymers when heated in more detail:

A
  • made up of polymer chains joined by intermolecular forces
  • heating the polymer causes the intermolecular forces to break, and now the polymer strands separate from each other and the polymer melts
  • cooling the melted polymer reforms the intermolecular bonds, meaning it goes back to a solid
88
Q

describe thermosetting polymers, and their structure:

A
  • don’t melt when we heat them
  • the polymer chains are connected to each other by strong crosslinks (covalent bonds). these aren’t broken by the heat, so they don’t melt when heated
  • instead, they burn at a higher temperature
  • plug cases are thermosetting polymers
89
Q

what is a use of ammonia, and how is it produced?

A
  • makes nitrogen based fertilisers for farming
  • the Haber process, which produces ammonia, however, is a reversible reaction, and so some ammonia breaks back down into nitrogen and hydrogen
90
Q

what is the production process of ammonia?

A
  1. nitrogen and hydrogen are mixed together NO REACTION
  2. they’re then compressed, increasing the pressure NO REACTION
  3. placed into a chamber at 450 degrees celsius with a powder iron catalyst, and this is when they’ll react together
  4. this produces ammonia. cool and condense it
  5. any nitrogen/hydrogen in gas form that hasn’t reacted is recycled
91
Q

where can nitrogen and hydrogen be sourced from?

A
  • nitrogen is extracted from the air
  • hydrogen can be produced by reacting methane with steam
92
Q

why is the catalyst powdered in the Haber process?

A

increases its surface area, making it more effective

93
Q

what is Le Chatelier’s principle, and how does this help with the Haber process?

A

states that if a system is at equilibrium, and a change is made to any of the conditions, the system responds to counteract the change
- we can therefore adjust the temperature and the pressure to shift the position of equilibrium towards the right hand side, producing more ammonia

94
Q

describe how we can change the temperature to produce more ammonia in the Haber process?

A
  • the forward reaction is exothermic
  • a relatively cool temperature will shift the position of equilibrium to the right hand side
  • however, a cool temperature will make the reaction slow, so we must compromise between the rate of reaction and the position of equilibrium
  • 450 degrees celsius is the compromise temperature, as we get a relatively fast rate and a relatively high yield of ammonia. the iron catalyst also increases the rate of reaction
95
Q

describe how we can change the pressure to produce more ammonia in the Haber process?

A
  • a high pressure will push the position of equilibrium to the right hand side, as it has less molecules
96
Q

describe temperature on the percentage of ammonia yield?

A
  • percentage of ammonia is highest at a relatively low temperature
  • a low temperature however reduces the rate, so if we increase the temperature, the rate is increased, but the yield is decreased
  • high temperatures also require more energy
97
Q

describe pressure on the percentage of ammonia yield?

A
  • percentage of ammonia increases at very high pressures
  • however, it’s very dangerous and expensive to work with very high pressure, so we settle on a compromise pressure of 200 atmospheres
98
Q

does a catalyst have any effect on the position of equilibrium?

A

no

99
Q

why are fertilisers critical for modern farming?

A

replace the elements which have been taken up by plants

100
Q

describe NPK fertilisers:

A
  • contain compounds of nitrogen, phosphorus, and potassium
  • these elements improve agricultural productivity, helping plants to grow larger and more rapidly
  • produced in large industrial facilities, where a variety of different raw materials are processed together to create the exact fertiliser required
  • they’re formulations of different salts, which contain the required elements in the percentages needed by the plants
101
Q

how are compounds of nitrogen in NPK fertilisers produced?

A
  • main compound is ammonium nitrate
  • use ammonia, produced by the Haber process, and use it to create nitric acid
  • react the nitric acid with more ammonia to make ammonium nitrate
102
Q

how are the compounds of potassium in NPK fertilisers produced?

A
  • comes from the salts potassium chloride or potassium sulfate
  • both of these are mined from the ground, and can be used directly without any further processing
103
Q

how are the compounds of phosphorus in NPK fertilisers produced?

A
  • phosphate rock is mined from the ground
  • it must be chemical processed before being used in fertilisers
104
Q

how do we treat phosphate rock with nitric acid?

A
  • treating it with nitric acid forms phosphoric acid and calcium nitrate
  • phosphoric acid contains phosphorus, but this can’t be directly added to plants - it must be neutralised with ammonia
  • this produces ammonium phosphate, which can be used in the NPK fertiliser
105
Q

how can we treat phosphate rock with sulfuric acid?

A
  • makes a mixture of calcium phosphate and calcium sulfate
  • this mixture is called single superphosphate, which can be used in NPK fertilisers
106
Q

how can we treat phosphate rock with phosphoric acid?

A
  • makes triple superphosphate
  • this can be used in NPK fertilisers
107
Q

compare the production of ammonium nitrate (reacting ammonia with nitric acid) in a school lab vs in the industry:

A
  • neutralisation reaction

SCHOOL LAB:
- dilute solutions of ammonia and nitric acid, making them safe to work with
- produce crystals using a water bath and a bunsen burner, requiring a lot of heat energy
- can only produce a small amount of ammonium nitrate in one go, a batch process

INDUSTRY:
- the ammonia is used as a gas, and the nitric acid is concentrated
- this is much more dangerous as the reaction is exothermic, so the heat produced must be safely removed. the heat is then used in later stages
- some of the heat energy for evaporation is provided by the earlier exothermic reaction
- the chemical is produced continuously, so thousands of kg can be produced easily

108
Q

describe natural fertilisers:

A
  • e.g. seaweed
  • uncertainty, as we’re unsure of its exact NPK composition

chemistry (12 decks)

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