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GCSE chemistry > water > Flashcards

water Flashcards

1
Q

describe the treatment of water supply.

A 
collected and stored in Reservoir 
sedimentation
filtration
chlorination 
storage
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2
Q

what is sedimentation?

A

when the larger solid particles settle on the bottom of the water under gravity

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3
Q

what is filtration?

A

giant filter beds made of sand and gravel, remove smaller insoluble particles

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4
Q

what is chlorination?

A

when chlorine is added to kill bacteria to prevent disease and make water safe to drink

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5
Q

what happens when the water is stored?

A

it is sent to users

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6
Q

name 2 advantages of fluoridation.

A

strong scientific evidence suggests it prevents tooth decay

it is found naturally in some water in some areas

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7
Q

name 4 disadvantages of fluoridation.

A

fluorine is harmful in large concentration
high intake has been linked to illness Eg - stomach cancer and infertility
mass medication
can be ingested elsewhere Eg - toothpaste

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8
Q

what is mass medication?

A

given to everyone wether it is needed or not

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9
Q

name the impurities found in rain water

A

dissolved gases such as carbon dioxide and water

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10
Q

name the impurities found in ground water

A

magnesium
calcium
sodium
potassium

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11
Q

name the impurities found in natural water

A

fertilizers
pesticides
household and industrial waste
natural pollution - bacteria and virus’

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12
Q

how is water conserved in hot summers?

A

stop people from watering gardens and washing their cars using hose pipes

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13
Q

describe distillation

A

boil the solution
steam given off will condense into pure water as it passes through the condenser
solid solution stays at the bottom of the flask

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14
Q

what is desalination?

A

the removal of salt from sea water

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15
Q

what are the disadvantages of desalination?

A

a lot of energy is needed which is expensive
produces green house gases
the salt is a pollutant and has to be disposed of carefully

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16
Q

how does distillation purify water?

A

ethanol boils first and turns into a gas which condenses back to a liquid
when all the ethanol boils, then water will boil

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17
Q

what are the disadvantages of distillation?

A

cannot obtain 100% ethanol because some water will evaporate at a lower temperature than its boiling point and pass through the condenser

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18
Q

what is hard water?

A

a type of water containing calcium and magnesium ions dissolved in it

19
Q

what is hard waters action with soap?

A

hard to form a lather

20
Q

what is soft water?

A

a type of water with few calcium and magnesium ions dissolved in it

21
Q

what is soft waters action with soap?

A

easy to from a lather

22
Q

how do you identify hard or soft water?

A

add soap solution to the water samples

measure the lather produced

23
Q

what is the result of the test for hard or soft water?

A

the more soap needed to lather the harder the water

24
Q

what are the advantages of hard water?

A

reduces likelihood of heart disease
strengthens teeth and bones
tastes nicer

25
Q

what are the disadvantages of hard water?

A

firs up kettles
forms scum with lime water
wastes soap
blocks pipes and boilers

26
Q

how do you soften permanently hard water?

A

add sodium carbonate

27
Q

what is symbol equation of softening permanently hard water?

A

Na2CO3 + Ca2+ —> CaCO3 + 2Na +

28
Q

how do you add sodium carbonate?

A

pass it through an ion exchange

29
Q

give an example of an ion exchange

A

a britta filter

30
Q

how do you soften temporary hard water?

A

by boiling

31
Q

what is the symbol equation for softening temporary hard water?

A

Ca(HCO3) —> CaCO3 + CO2 + H2O

32
Q

how do you regenerate an ion exchange?

A

rinse in sodium solution

33
Q

why do you have to regenerate an ion exchange?

A

because 2 sodium ions are needed for 1 calcium ion

34
Q

what are the advantages of boiling water to soften it?

A

easy to do

no expensive equipment needed

35
Q

what are the disadvantages of boiling water to soften it?

A

doesn’t remove permanently hard water

forms limescale

36
Q

what are the advantages of using an ion exchange?

A

removes temporary and permanently hardness

uses cheap concentrated sodium solution

37
Q

what are the disadvantages of using an ion exchange?

A

exchange columns are expensive

38
Q

what are the advantages of adding sodium carbonate to soften water?

A

removes both temporary and permanently hard water

39
Q

what are the disadvantages of adding sodium carbonate to soften water?

A

forms limescale

40
Q

what does solubility mean?

A

a measure of the maximum mass of a solid that can be dissolved in a quantity of water

41
Q

how do you measure solubility?

A

add a solid to the water at different temperatures
filter to remove undissolved solid
dry the solid and measure its mass

42
Q

what is the equation used to measure solubility?

A

mass of the undissolved solid - original mass

43
Q

how does an ion exchange filter work?

A

the water passing through replaces the calcium ions with sodium ions

44
Q

exam tip: how much solid would be precipitated if a saturated solution were cooled

A

read from graph of two temps given and take them away from each other

GCSE chemistry (8 decks)

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