Water & Air
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What type of substances are formed when burnt in air?
Oxides
Are oxides of non-metals acidic / non acidic?
Acidic
Acid + Carbonate = ?
A salt + water
What are the 2 types of salts than can exist?
Anhydrous and hydrated
Describe a chemical test for identifying water.
Add the liquid to anhydrous cobalt (II) chloride. Turns pink to blue. Cobalt (II) chloride paper can also be used. CoCl2(s) +6H2O(l) becomes CoCl2.6H2O(s)
Describe a chemical test for identifying water (2)
Add the liquid to be tested to anhydrous copper (II) sulphate solid. The powder turns from white to blue as hydrated sopper (II) sulphate forms. CuSO4(s) + 5H2O (l) CuSO4. 5H2O (s)
Describe the water cycle
Water evaporates from the sea Water vapor condenses to form clouds Water droplets in the clouds come large enough to fall as rain Water falls on the land and rivers and seas flow the water back to the sea.
What happens to the demand for drinking water as the population rise?
It increases.
Describe how water is processed to make it suitable for drinking
Water goes from reservoirs to a treatment plant Filtered through coarse gravel to remove large bits of dirt Filtered through beds of fine gravel and sand to remove small particles Chlorine is passed through it to kill bacteria (in some areas also sodium fluoride is added to stop tooth decay) Water is supplied to homes and industry
Which gases in what % is clean air composes of?
Nitrogen 78% Oxygen 21% Argon 0.9% Carbon dioxide 0.04% Trace amounts of other noble gases and water vapour 0.06%
Which cycles keep the composition of air stable?
Nitrogen cycle and carbon cycle.
How long has air had its current composition?
200 million years
What type of impurities does water contain before treatment?
Soluble (dissolved calcium, metal compounds, inorganic pollutants) and insoluble (soil, pieces of plant other organic matter).
What are examples of diseases in untreated water?
Cholera and typhoid
Name some common pollutant gases that occur in the air?
Carbon monoxide, sulphur dioxide, oxides of nitrogen and lead compounds from leaded petrol.
What gas are the various forms of rust protection trying to exclude?
Oxygen
Name 4 types of rust protection
Galvanizing/sacrificial protection, painting, plastic coating, covering with grease/oil
Which gases contribute to climate change?
Carbon dioxide and methane
Describe the separation of oxygen and nitrogen by fractional distillation.
Air is filtered to remove the dust Air is cooled to -80oC so Carbon dioxide and water vapour solidify and can be removed. Air is cooled further compressed and then allowed to expand quickly. Causes further cooling. At -200 oC the air becomes liquid. The air is fractionally distilled using a fractionating column which separates liquids with different boiling points. Boiling point of oxygen -183 oC Boiling point of argon -186 oC Boiling point of nitrogen -196 oC
Name 2 commercial uses for oxygen
Medical – supporting patients with breathing difficulties. (There has been a shortage of oxygen during Covid.) Mixed with hydrocarbons such as ethyne for use in cutting tools
Name 2 commercial uses for nitrogen
It is very unreactive – used in food packaging to stop oxidation and decay. (e.g. bags of lettuce leaves stay fresh for longer.) Used to reduce fire hazards in military aircraft systems. Used in production of ammonia. Used in production of silicon chips.
How is water used in industry?
Coolant for industrial processes e.g. nuclear power plant. Watering crops. As a solvent in many chemical production processes. Hydro electric power stations to generate electricity.
What are the uses of water in homes?
Drinking, cooking and washing, general sanitation, car radiators, for gardens and plants.
What problems arise when the supply of water in inadequate?
Food shortages and famine due to the lack of crops Spread of bacteria and disease as drinking water becomes infected due to poor sanitation.