Water Flashcards
Why arent water sources clean
bacteria,dissolved substances and solids
Define potable water
water that is safe to drink
Define pure water
100% H20
What is surface water
water in lakes and such
What is ground water
water collected form rains underground
How is fresh water supplies turned into potable water
By passing water through filters beds and sterilising the water to kill microbes (chlroine,ozone and UV)
What do countries do if there is a lack of fresh water supply
Desalination
What is desalination
process of removing salt from saltwater
How is desalination done
- Distillation ( Heated up so salt is left behind and steam is condensed)
- Using membranes e.g. reverse osmosis
Define Reverse Osmosis
Water is put under high pressure and passed through a membrane which has tiny pores in it. The pores allow water molecules through but prevent most ions and molecules from passing through.
What are the disadvantages of reverse osmosis
It is expensive and not v efficient due to producing waste water
What are the 4 stages of waste water treatment
1) Screening and grit removal to remove large particles
2) Sedimentation allows tiny particles to settle out from still water
3) Sewage sludge digested anaerobically
4) The effluent is treated with aerobic bacteria to reduce the volume of solid waste
What are the findings of the required practical for analysis and purification of water
- sea water contains the most molecules followed by mineral water hen rain and distilled water has none
- Sea water is alkaline and distilled water is neutral. Mineral water/rain water are acidic
Define saturation
when a solution can no longer dissolve any more g/100cm3 of water at a given temp.
What is saturation dependent on
dependent on temperature and generally a higher temp. means more solute can be dissolved
What is solubility of a solute
the maximum amount that can dissolve in 100 grams of water at a given temp.
What is solubility of a solute
the maximum amount that can dissolve in 100 grams of water at a given temp.
Define soluble
If a substance is soluble it will dissolve in a given amount of liquid, called the ‘solvent’.
What is a solute
the substance being dissolved by the solvent
What does a solubility curve show
the relationship of solubility and temperature on a range of substances
An example of calculating solubility to learn
Example: 12 g of potassium sulphate dissolve in 75 grams of water at 60 o C.
What is the solubility in water at that temperature?
75 g of water dissolves 12 g of potassium sulphate
So 1 g of water dissolves 12/75 g of potassium sulphate
So 100 g of water dissolves 12/75 x 100 = 16 g of potassium sulphate
The solubility of potassium sulphate in water at 60 o C is 16 grams.
How do you test for water using Anhydrous copper (II) sulphate
It turns from white to blue in presence of water
How do you test for water using anhydrous cobalt (II) chloride
It turns from blue to pink in presence of water
