Note:

IGCSE Chemistry Notes on Air and Water

Syllabus Objectives:

11.1 Water

Core 

• Describe chemical tests for water using cobalt(II) chloride and copper(II) sulfate 
• Describe, in outline, the treatment of the water supply in terms of filtration and chlorination • Name some of the uses of water in industry and in the home

Supplement 

• Discuss the implications of an inadequate supply of water, limited to safe water for drinking and water for irrigating crops

11.2 Air

Core 

• State the composition of clean, dry air as being approximately 78% nitrogen, 21% oxygen and the remainder as being a mixture of noble gases and carbon dioxide 
• Name the common pollutants in the air as being carbon monoxide, sulfur dioxide, oxides of nitrogen and lead compounds 
• State the source of each of these pollutants: – carbon monoxide from the incomplete combustion of carbon-containing substances – sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds (leading to ‘acid rain’) – oxides of nitrogen from car engines – lead compounds from leaded petrol
• State the adverse effect of these common pollutants on buildings and on health and discuss why these pollutants are of global concern 
• State the conditions required for the rusting of iron
• Describe and explain methods of rust prevention, specifically paint and other coatings to exclude oxygen

Supplement 

• Describe the separation of oxygen and nitrogen from liquid air by fractional distillation
• Describe and explain the presence of oxides of nitrogen in car engines and their catalytic removal 
• Describe and explain sacrificial protection in terms of the reactivity series of metals and galvanising as a method of rust prevention

11.3 Nitrogen and fertilisers

Core 

• Describe the need for nitrogen-, phosphorus- and potassium-containing fertilisers 
• Describe the displacement of ammonia from its salts

Supplement

• Describe and explain the essential conditions for the manufacture of ammonia by the Haber process including the sources of the hydrogen and nitrogen, i.e. hydrocarbons or steam and air

11.4 Carbon dioxide and methane

Core

• State that carbon dioxide and methane are greenhouse gases and explain how they may contribute to climate change 
• State the formation of carbon dioxide: – as a product of complete combustion of carbon-containing substances – as a product of respiration – as a product of the reaction between an acid and a carbonate – from the thermal decomposition of a carbonate 
• State the sources of methane, including decomposition of vegetation and waste gases from digestion in animals Supplement 
• Describe the carbon cycle, in simple terms, to include the processes of combustion, respiration and photosynthesis