More Lessons for IGCSE Chemistry
A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).
Extraction of oxygen and nitrogen from liquid air
How do you extract oxygen, nitrogen, argon?
What are the properties for oxygen, nitrogen, and argon?
How air pollution is any chemicals in the atmosphere that negatively affect human health?
Primary pollutants (like CO, VOCs, NOx, SO2
, PM, and Lead) as well as secondary pollutants (like Ozone, nitric acid, and sulfuric acid) are included.
Regulation of air pollution and technology can mediate the health threat.
How Does Water Treatment Work?
Learn the basics about water treatment, as a part of environmental chemistry.
Human beings have added to the natural water cycle by taking water from rivers for use in our towns and cities.
We are taking a huge amount of water from natural sources to use in our homes and industries.
Lots of humans take water for granted. For some people water is a precious and scarce resource. Only 3% of the water in the world is fresh. Of this, three quarters is locked up as ice, one quarter is under ground and only 1% is above ground in rivers and lakes.
Global demand for water is increasing hugely.
Water is mainly used for irrigation of crops, and normally this needs no further purification. The next biggest user is industry. Sometimes, for example in food preparation very clean water is needed. Finally there is the domestic water.
Some people are lucky enough to have domestic water piped to their house, and this is usually of drinkable quality and so undergoes treatment first.
Piped water from the water works originally comes from rivers, lakes, reservoirs, or underground aquifers. A grill stops large floating objects, such as fish, from entering the water works.
Next coagulants, such as Alum, are added which causes tiny particles in the water to cluster in lumps which then settle in the sedimentation process. The filter is made of fine sand to capture any particles that are left. Finally chlorine is added to kill any bacteria. If the water does not naturally contain fluoride ions they are often added as sodium fluoride as an aid to build strong teeth in those that drink the water.
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