Water Flashcards
Soft water readily forms what with soap?
Lather.
Hard water reacts with soap to form what?
Scum.
What means more soap is needed to form a lather in hard water?
The hard water reacts with soap to form scum so more soap is needed to produce a lather.
Soapless detergents don’t form what in hard water?
Scum.
Hard water contains what?
Dissolved compounds, usually calcium or magnesium.
How is hard water usually made hard?
When it comes into contact with rocks and compounds dissolve in it making it hard.
What are the two types of hard water?
Temporary and permanent hard water.
What is the difference between temporary and permanent hard water physically?
Permanent hard water remains hard when boiled whereas temporary hard water softens when boiled.
What makes temporary hard water soften when boiled?
It contains hydrogencorbonate ions (HCO3-) that decompose when heated to produce carbonate ions that react with the calcium and magnesium ions in the hard water. These reactions form precipitates which mean the water is no longer hard.
Using hard water does what to cost?
Increases cost because more soap is needed.
When temporary hard water is heated it produces what the reduces efficiency of heating systems and kettles?
Scale.
Benefits of hard water:
Calcium compounds are good for development and maintenance of bones and teeth.
Calcium compounds help to reduce heart disease.
Hard water can be made soft by which two methods?
Adding sodium carbonate.
Using ion exchange columns.
How does adding sodium carbonate make hard water softer?
it rects with the calcium and magnesium ions and the sodium is displaced them making precipitates of calcium carbonate and magnesium carbonate.
How do ion exchange columns make hard water softer?
They contain hydrogen ions or sodium ions which displace the calcium or magnesium ions as they pass through the column making the water softer.
For humans to drink water it should have sufficiently low levels of what?
Dissolved salts and microbes.
Water of the correct quality is produced by:
Choosing an appropriate source.
Passing water through filter beds to remove any solids.
Sterilising with chlorine.
What in water filters can remove some dissolved substances from tap water to improve the taste and quality?
Carbon, silver and ion exchange resins.
Chlorine may be added to drinking water to…
…remove microbes.
Florine may be added to drinking water to…
…improve dental health.
Pure water can be produced how?
By distillation.
Distillation requires a large amount of what meaning it has a high cost?
Energy.
