Using the Earth's resources and obtaining potable water

• What would you see when sodium hydroxide solution is added drop by drop to tap water containing aluminium ions?

  produces a white precipitate which dissolves
• Why is the water sterilised?

  Kill microbes
• Why do some water companies add fluoride to drinking water?

  chloride ions are bigger than water
• The student could show that the filtered water contains dissolved salts without using a chemical test. Describe how.

  put a sample of the filtered water in an evaporating basin there will be crystal salt left
• Suggest two reasons why copper should not be disposed of in landfill sites

  Copper ores are limited

  They can be recycled
• Sea water is not used as drinking water. Suggest why.

  Contains dissolved solids
• Explain why water for drinking is filtered and then treated with chlorine.

  filtered: removes solids

  chlorine: kills microbes
• What are the two main steps used to treat water from lakes? Give a reason for each step

  filtration by passing through filter beds to remove solids

  sterilisation to kill microbes
• Explain why it is more difficult to produce drinking water from waste water than from water in lakes.

  Water needs a different process as it has more microbes
• How could the water be tested to show it is pure? Give the expected result of the test for pure water.

  determine boiling point should be at a fixed temperature 100°C
• Why is producing drinking water from sea water expensive?

  Requires a lot of energy
• What is in water filters that removes hardness from water?

  Ions exchange resin
•  Why is distillation not usually an economic method of treating water for drinking?

  High cost of energy
• state one health benefit of drinking hard water

  maintain bones
• The reaction in the furnace could cause environmental pollution. Explain how.

  Produces sulfur dioxide that causes acid rain
• What is used in phytomining to remove copper compounds from the land?

  Plants
• The amount of chlorine in swimming pool water should be carefully monitored and controlled. Explain why

  Chlorine is toxic so too much is dangerous

   
• What is the meaning of the term ore?

  contain enough metal to make it economical
• What type of reaction produces the iron?

  reduction
• Describe how cracking is carried out.

  Heated hydrocarbons passed over a catalyst
• Suggest three reasons why the kettle should not be disposed of in a landfill site.

  metal may not corrode away

  plastic doesn’t break down

  water pollution
• What is potable water?

  Drinking water that has sufficiently low levels of salts and microbes.
• How is potable water different to pure water?

  Pure water contains water only. Potable water contains some dissolved salt.
• Where does fresh water come from in the UK?

  Rainwater that collects in rivers, lakes and the ground.
• How is most potable water produced so it is safe?

  Water from lakes is passed through filter beds and sterilised.
• Why is fresh water passed through filter beds?

  To remove insoluble solids.
• Why is fresh water sterilised?

  To kill harmful microbes.
• How is fresh water sterilised?

  By adding chlorine, ozone or exposing to UV radiation.
• How can potable water be made if fresh water is limited?

  Desalination of sea water or salty water (brine).
• Name two examples of desalination.

  Distillation and reverse osmosis.
• How does reverse osmosis work?

  Water is forces through a membrane that prevents salt from passing under high pressure.
• What is the disadvantage of desalination?

  They require a lot of energy and are expensive.