Water

Water

1. Hardness of water

   • Soft water produces a good lather with soap whereas hard water produces scum (unless a soapless detergent is used); to get a good lather, more soap has to be used so more money is spent
     • This is because dissolved calcium and magnesium ions in the soap react with the soap to make scum which is insoluble
       • When heated, hard water also produces scale (calcium carbonate) on the inside of boilers, pipes and kettles; if bad, scale can decrease efficiency or even block pipes and boilers to the point of replacement
         • Scale also decreases the efficiency of kettles by gathering on the heating element and insulating it, meaning it takes longer to boil
       • Rain falling on rocks can dissolve compounds like magnesium sulphate and calcium sulphate
         • This, however, can be a good thing as calcium is good for teeth and bones and studies have found that people living in hard water areas have less risk of developing heart disease
           • Also, some people believe it tastes nicer
   • There are two types of hardness: temporary (caused by the hydrogencarbonate ion) and permanent (caused by calcium sulfate)
     • Temporary hardness is removed by boiling as the calcium hydrogencarbonate decomposes when heated to make calcium carbonate which is insoluble; this is the scale in kettles
       • Either hardness can be can be softened by adding washing soda (sodium carbonate) which precipitates out calcium and magnesium ions
         • Either hardness can also be softened by an ion exchange column which contain sodium ions that are exchanged for the calcium and magnesium ions in the water
   • Hardness of water can be compared by measuring the amount of soap needed to make a permanent lather; the water can then be boiled and tested again to see if the hardness is temporary or permanent

2. Water Quality

   • Water can contain some poisonous salts or harmful microbes which cause cholera and dysentery
     • Drinking water mostly comes from reservoirs which flows in from rivers and groundwater; from the reservoir, water goes through a water treatment process
       • The water passes through a mesh screen to remove big things such as twigs
         • From here chemicals are added to make solids and microbes stick together and fall to the bottom; the water then passes through a filter to remove these solids
           • Water is then chlorinated to kill any remaining harmful microbes
             • Some people don't like chlorine being in their water so they buy filters containing carbon or silver which removes chlorine tastes and supposedly kills bugs, respictively
   • Completely pure water is called distilled water and is made by boiling water to make steam which is then condensed
     • This method uses too much energy and costs too much to be used as tap water
   • Fluoride and chlorine is sometimes added to water because fluorine reduces tooth decay and chlorine is added to prevent disease
     • However some studies have linked chlorine in water to an increase in cancers; chlorine can react with natural substances in the water to make toxic by-products which some people think causes cancer
     • In high doses, fluoride can cause cancer and bone problems in humans so some people think it shouldn't be added to drinking water
       • This causes concern about whether it's right to mass medicate; people can choose whether or not they have fluoride toothpaste but can't choose whether their tap water has fluoride in it