Higher:
Can describe the difference between potable and pure water and the steps used to produce potable water from fresh water and from salty water
Middle:
Lower:
Lesson Starter: Adult humans are 60 percent water, and our blood is 90 percent water. Water is essential for the kidneys and other bodily functions. When dehydrated, the skin can become more vulnerable to skin disorders and wrinkling. Drinking water instead of soda can help with weight loss. What other water facts can you think of?
Lesson Starter Slide
Iggy Pont Lezica from Thames Water tells us about how sewage water is treated to supply us water that is safe to drink.
Expert Film
Using the handout pupils need to define the terms:
• potable water
• pure water.
Explain the differences between the two terms.
Extended writing: describe the process of desalination.
Extended writing: describe the process of distillation
Extended writing: explain why distillation separates substances.
Explain what happens to substances during the process of distillation in terms of intermolecular forces of attraction.
Handout
Explain the differences between the two terms.
Extended writing: describe the process of desalination.
Extended writing: describe the process of distillation
Extended writing: explain why distillation separates substances.
Water of appropriate quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microbes. Water that is safe to drink is called potable water. Potable water is not pure water in the chemical sense because it contains dissolved substances.
The methods used to produce potable water depend on available supplies of water and local conditions.
In the UK, rain provides water with low levels of dissolved substances (fresh water) that collects in the ground, in lakes, and rivers, and most potable water is produced by:
Sterilising agents used for potable water include chlorine, ozone or ultra-violet light.
If supplies of fresh water are limited, desalination of salty water or sea water may be required. Desalination can be done by distillation or by processes that use membranes such as reverse osmosis. These processes require large amounts of energy.
Distinguish between potable water and pure water. Describe the differences in treatment of ground water and salty water. Give reasons for the steps used to produce potable water.
Communicating the scientific rationale for investigations, including the methods used, the findings and reasoned conclusions, using paper-based and electronic reports and presentations