GCSE Chemistry C1 (OCR)

Question	Answer
Which gases make up the atmosphere?	Mainly nitrogen, oxygen, and argon, plus small amounts of water vapour, carbon dioxide, and other gases.
What are the relative proportions of the main gases in the atmosphere?	78% Nitrogen 21% Oxygen 1% Argon
How was the Earth's early atmosphere formed?	Volcanoes gave out huge amounts of carbon dioxide and water vapour, and also some nitrogen and methane.
What happened when the Earth cooled?	Water vapour condensed to form oceans, and some of the carbon dioxide dissolved in the oceans and later became incorporated in sedimentary rocks.
What impact did the evolution of photosynthesising organisms have on the atmosphere?	They used up carbon dioxide during photosynthesis and released oxygen. So, the oxygen level rose and the carbon dioxide level fell.
How has human activity changed the composition of the atmosphere?	Small amounts of carbon monoxide, nitrogen oxides and sulfur dioxide has been added. Extra carbon dioxide and small particulates have also been added.
How are some pollutants harmful to humans?	Carbon Monoxide - Changes the amount of oxygen in the blood, making existing heart conditions worse. Nitrogen Dioxide - Can cause breathing problems and make asthma worse. Particulates - Can be breathed into the lungs and can make asthma and lung infections worse.
How are some pollutants harmful to the environment?	Sulfur Dioxide - Reacts with water and oxygen to form acid rain. Carbon Dioxide - Excess levels can increase global warming. Nitrogen Monoxide - Reacts in the atmosphere to form Nitrogen Dioxide. Nitrogen Dioxide - Reacts with water and oxygen to produce acid rain. Particulates - Deposited on surfaces, making them dirty.
What is coal mainly made up from?	Carbon
What are petrol, diesel, and oil mainly compounds of?	Hydrogen and Carbon (Hydrocarbons)
What happens when fuels burn?	Atoms of carbon and/or hydrogen from the fuel combine with atoms of oxygen from the air to produce carbon dioxide and/or water.
What is oxidation?	A reaction when a substance combines with oxygen.
What is reduction?	A reaction that removes oxygen from a substance.
Fuels burn more _________ in _________ than in ________.	Rapidly Pure Oxygen Air
How does burning fossil fuels in power stations and in transport pollute the atmosphere?	Carbon Dioxide and Sulfur Dioxide are formed. Carbon Monoxide and Particulate Carbon are formed from incomplete combustion. Nitrogen Oxides are formed from the reaction between nitrogen and oxygen at high temperatures inside engines.
How can atmospheric pollution caused by power station be reduced?	- By using less electricity - By removing sulfur from natural gas and fuel oil - By removing sulfur dioxide and particulates from the flue gases emitted by coal-burning power stations
How can sulfur dioxide be removed from flue gases?	By wet scrubbing. Sulfur dioxide is an acid gas, so absorbing it with an alkali (eg. seawater) means that the sulfur dioxide can be removed easily. It can also be mixed with calcium oxide to form a new solid chemical, calcium sulfate, which can then be collected and removed.
How can particulates be removed from power stations?	By passing them through an electrostatic precipitator, which contains electrically charged plates. The particulates pick up a negative charge, are attracted to the positive plate, and are then collected and removed.
What is the only way of producing less carbon dioxide?	By burning less fossil fuels.
How can atmospheric pollution caused by exhaust emissions be reduced?	- Burning less fuels (eg. having more efficient engines) - Using low sulfur fuels - Using catalytic converters - Increasing public transport - Having legal limits to exhaust emissions (enforced by MOT tests)
How does a catalytic converter work?	Carbon monoxide is turned into carbon dioxide. Nitrogen monoxide in converted into nitrogen and oxygen.

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GCSE Chemistry C1 (OCR)

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