This question is about pollutant gases. (a) Hydrocarbons such as octane are used as fuels for cars. The list shows the gases present in a car exhaust. carbon dioxide carbon monoxide nitrogen nitrogen dioxide octane water vapour

1. (a)State which two gases in the list show that incomplete combustion has taken place in this car engine. 1 2[2]
2. (b)Describe a test for carbon dioxide. test observation[2]
3. (c)Two natural sources of methane in the atmosphere are from leaks of natural gas and waste gases from animals. Give one other natural source of methane in the atmosphere.[1]
4. (d)Complete this sentence about the effect of an increase in the concentration of methane in the atmosphere. Methane is a gas because it absorbs and then re-emits infrared radiation. This contributes to an increase in temperature of the atmosphere which is called[2]
5. (e)Cars are fitted with catalytic converters to reduce the amount of harmful pollutant gases from car exhausts. Describe how catalytic converters remove pollutant gases from car exhausts.[3]