C1 OCR 21st Century Science Revision Cards

A1) oxygen ~21%, carbon dioxide ~0.03%, nitrogen ~78%, and argon ~1%.

A2) Carbon dioxide + water à oxygen + glucose + energy 

A3) Water and carbon dioxide

A4) Hydrocarbons with sulphur impurities when burned (combustion) are oxidised i.e. sulphur binds with oxygen creating sulphur dioxide. This occurs during burning of fossil fuels and is realised into the air from factories and will dissolve in water vapour in the air. This creates sulphuric acid (aq) that collectively with other gases that dissolve in water to create acids can be termed acid rain. 

A5) Soil becomes acidic and it causes difficulties when growing crops. Destruction of habitats such as trees and lakes when they become overly acidified, this can also kill wild life. Destruction to marble statues and buildings made from limestone calcium carbonate due to neutralisation reaction with the acid rain. 

A6) Air (nitrogen and oxygen) inside a car engine is caused to combine due to a high electrical spark from the spark plug that breaks the bonds between molecules of oxygen and nitrogen and they can then form new bonds with each other. The other source is natural and comes from lightning but has the same mechanism for production of nitrogen dioxide. (N.B. 80% roughly comes from cars, burning fossil fuels due to the heat energy instead of electrical energy breaking the bonds, small percentage from lightning.)

A7) 15-19 is the range and the mean is 17 micrograms per meter squared. 

A8) An outlier is a result that does not fit with the general pattern of results established. 

A9) Correlation is a statistical measurement of the relationship between two variables. 

A10) More efficient engines, using low sulphur fuels, using catalytic converters in which nitrogen monoxide is reduced and carbon monoxide is oxidised, having legal limits to emissions from cars, encouraging more environmentally friendly ways of transport e.g. car pooling/public transport etc. 

A11) A catalytic converter is an exhaust emission control device which converts toxic chemicals in the exhaust of an internal combustion engine into less noxious substances. For example, carbon monoxide is converted to carbon dioxide and nitrogen monoxide/dioxide is converted back into oxygen and nitrogen.

A12) It contains a triple covalent bond (i.e. each nitrogen has three hands and they hold each other tightly)

A13) The most common method uses calcium oxide (lime), which is mixed with water to make an alkaline slurry. This is used to scrub the sulphur dioxide out of the chimney with the lime reacting with the sulphur dioxide to form calcium sulphate that can be sold for profit. Power stations near the sea use sea water as a coolant that is slightly alkaline and will react with the sulphur dioxide with air used to oxidise the product to sulphate. Seawater is returned to the sea but large volumes required for this method