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Flashcards in C1c Deck (13):

What does air contain?

Oxygen, nitrogen, water vapour and carbon dioxide.


How does photosynthesis, respiration and combustion affect the level of carbon dioxide and the level of oxygen in the air?

Respiration and combustion of plants and animals add carbon dioxide to the air and remove oxygen. Photosynthesis does the opposite - it removes carbon dioxide and adds oxygen. These processes should all balance out. However, humans have upset the natural carbon cycle, which has affected the balance of gases in the atmosphere.


What are oxygen, nitrogen and carbon dioxide levels in the present day atmosphere?

Approximately constant.


What is the percentage composition of clean air?

21% oxygen.
78% nitrogen.
0.035% carbon dioxide.


How does deforestation effect the composition of air?

Chopping down trees is deforestation and plants are the main things taking carbon dioxide out of the atmosphere - so fewer plants means less carbon dioxide is taken out of the atmosphere.


How does population effect the composition of air?

The human population is increasing, meaning more people are respiring, giving out more carbon dioxide. More people means more energy is needed for lighting, heating, cooking and transport. More countries are also becoming industrialised. This means the average energy demand per person is also increasing.. This increased energy consumption comes mainly from the burning of fossil fuels, which releases more carbon dioxide.


What is one possible theory for how the present day atmosphere evolved over millions of years?

Degassing - volcanoes erupting, releasing gases from inside the earth - of early volcanoes producing an atmosphere rich in water and carbon dioxide.
Condensing of water vapour to form oceans.
Dissolving of carbon dioxide in the ocean waters.
Relative increase of nitrogen due to its lack of reactivity.- it was being made but not broken down.
Development of photosynthetic organisms and increase in oxygen due to photosynthesis.


What are the three common pollutants found in the air ?

Carbon monoxide - a poisonous gas formed by the incomplete combustion of petrol or diesel in car engines.
Oxides of nitrogen - causes photochemical smog and acid rain and are formed in the internal combustion engine.
Sulfur dioxide - causes acid rain that will kill plants, kill aquatic life, erode stonework and corrode metals and is formed when sulfur impurities in fossil fuels burn.


Why do high temperatures inside an internal combustion engine allow nitrogen from the air to react with oxygen to make oxides of nitrogen?

When fuels are burned in vehicle engines, high temps are reached. This make nitrogen and oxygen from the air combine.


What does a catalytic converter do?

Removes carbon monoxide from the exhaust gases of a car and changes it into carbon dioxide.


Why is it important that atmospheric pollution is controlled?

The build-up of all these pollutants can make life unhealthy and miserable for many humans, animals and plants. The number of cases of respiratory illnesses (e.g. asthma) has increased in recent years - especially among young people. To prevent acid rain and reduce greenhouse gases.


What is the symbol equation for a catalytic convertor?

2CO + 2NO = N2 + 2CO2


Why may carbon monoxide, oxide of nitrogen and sulfur dioxide levels be decreasing?

Carbon monoxide levels have decreased because car engines are becoming more efficient. Catalytic convertors, 2CO + 2NO = N2 + 2CO2, removes carbon monoxide by converting it into carbon dioxide. Sulfur dioxide levels have decreased because there is less coal burning which is a major contributor and it is removed from waste gases after combustion of the fuels.