C3 - Water Flashcards
What turns water hard?
When water flows across the rocks either calcium or magnesium ions are added.
What happens when hard water reacts with soap?
A scum is formed so more soap is needed to form a lather.
How to soften hard water?
Permanent hard water remains hard upon boiling.
Temporary hard water can be softened by boiling. The water contains hydrogen carbonate ions which are decomposed when the water is boiled. The carbonate ions then react with the calcium or magnesium ions within the water to form Calcium Carbonate or Magnesium Carbonate which is scale.
How does scale have negative impacts?
Scale can clog up pipes.
It costs more to heat up the boiler because the scale must be heated too.
What does hard water contain?
Hardwater contains calcium which is good for bones and teeth.
What happens when soft water reacts with soap?
It forms a lather.
How can hard water be turned soft?
There are two methods.
Adding sodium carbonate/washing soda to the hard water causes the calcium and magnesium compounds to react with the sodium carbonate and precipitate out of the solution as an insoluble solid leaving the water soft.
Ion exchange resins can be used. Hard water passes through a column which contains a resin with either hydrogen or sodium ions in. The calcium and magnesium ions exchange places with the hydrogen or sodium ions. The hydrogen or sodium ions do not cause hardness so the water is now soft.
How can good quality water be produced?
A good source must be chosen.
The water can be then passed through many filter beds which will remove any solid particulates.
It must be sterilised by chlorine which will kill off any bacteria and microbes.
Water filters containing carbon, silver and ion exchange resins can remove some dissolved substances from tap water to improve the taste and quality.
Why would fluoride be added?
Fluoride can be added to improve dental health.
Advantages:
Water fluoridation helps protect adults and children from tooth decay.
It saves expenses requires to treat the disease.
It can save your family from the pain and discomfort of toothache.
It provides additional protection with fluoride toothpaste.
Disadvantages:
It is a form of mass medication and some people may be upset they have no choice whether or not to have it.
Too much fluoride can cause mottling of the teeth.
Fluoride is only a benefit to growing children, adults get limited benefit.
Fluoride is not needed if proper care of the teeth it taken.
How can pure water be produced?
By distillation. Water is boiled then the steam is condensed. A large amount of energy is needed to boil the water so costs are high.
