Water Flashcards
What does soft water form?
lather with soap
Hard water reacts with soap to form:
scum and so more soap is needed to lather
What do soapless detergents not form?
scum
What does hard water contain?
Dissolved compound, usually of calcium or magnesium. the compounds are dissolved when water comes in contact with rocks
What are the 2 types of hard water?
Permanently hard water = water remains hard when boiled
Temporarily hard water = water is softened by boiling
What does Temporary hard water contain?
Hydrogencarbonate ions (HCO3 ^-) that decomposes on heating to produce carbonate ions which react with calcium and magnesium ions to form precipitates
What is the disadvantage of using hard water?
It increases costs because more soap is needed.
When temporary hard water is heated it can produce scale that reduces the efficiency of heating systems and kettles
What are the benefits of using hard water?
Calcium compounds are good for the development and maintenance of bones and teeth and also help to reduce heart disease
How is hard water made soft?
By removing the dissolved calcium and magnesium ions. This can be done by:
- Adding sodium carbonates, which react with eh calcium and magnesium ions to form a precipitate of calcium carbonate and magnesium carbonate
- Using commercial water softeners such as ion exchange columns containing hydrogen ions or sodium ions, which replace the calcium and magnesium ions when hard water passes through the column
How is water of the correct quality is produces by?
Choosing an appropriate source
Passing the water through filter beds tp remove any solids
sterilising with chlorine
Why is water important?
Water of the correct quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microbes
What do water filters do and how do they work?
Water filters containing carbon, silver and ion exchange resins can remove some dissolved substances from tap water to improve the taste and quality
What happens when chlorine is added to drinking water?
It reduces microbes and fluoride may be added to improve dental health
Pure water can be produced by…
distillation
Cons of producing pure water by distillation are…
Large amounts of energy is needed for distillation and, as a consequence, this leading to high costs levels
