Potable Water Flashcards
What is potable water?
Potable water is water that contains minerals and is safe for humans to drink, it isn’t pure.
How is water from fresh water sources treated?
1) A wire mesh screens out large materials(twigs etc).
2) Then gravel and sand beds filter out any other solid pieces.
3) The water is then sterilised to kill any harmful bacteria or microbes. This can be done by bubbling chlorine gas or by using ozone or ultraviolet light.
How can distillation be used to desalinate sea water?
1) The sea water is poured into a distillation apparatus and is the flask is heated from below.
2) The water will boil and form steam, leaving any dissolved salts in the flask.
3) The steam will then condense back to liquid water in the condenser and can be collected.
How can be reverse osmosis be used to desalinate sea water?
The sea water is passed through a membrane with tiny pores, which allows water molecules to pass through but traps large ions or molecules.
What are the two methods used to desalinate sea water?
Distillation and reverse osmosis.
Why is fresh water used instead of sea water?
Sea water contains a lot of sodium chloride which means distillation and reverse osmosis is used, but these methods require a lot of energy and are very expensive. Also they’re not practical for producing large quantities of fresh water.
How do you analyse water samples to check for sodium chloride?
1) Test the pH of the water using a pH meter. If it’s too high or low, neutralise it. Don’t use an indicator to test the pH as this could contaminate the water.
2) Test a sample of water for sodium ions by doing the flame test. If sodium ions are present, the flame will turn yellow.
3) Test another sample of water for chloride ions by adding a few drops of dilute nitric acid and silver nitrate solution. If chloride ions are present, a white precipitate will form.
