11.5 atmospheric pollutants
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what do fossil fuels contain
• hydrocarbons • sulphur
why is the sulphur is fossil fuels bad
• reacts with oxygen when a fossil fuel is burnt to form sulphur dioxide • this acidic gas is toxic
what does sulphur dioxide do
• bad for the environment • cause of acid rain • acid rain damages trees and kills animal and plant life in lakes • also attacks buildings (especially those made of limestone) and metal structures
how can sulphur impurities be removed from a fuel before it is burnt
• happens in petrol and diesel for cars • in gas-fired power stations • in coal fired: can be removed from waste or ‘flue’ gases by reacting it with basic calcium oxide or calcium hydroxide
what happens when any fuel containing carbon is burnt
it produces carbon dioxide
incomplete combustion def
when a fuel burns in insufficient oxygen, producing carbon monoxide as a toxic product
nitrogen oxides def
gaseous pollutants given off from motor vehicles, a cause of acid rain
particulates def
small solid particle given off from motor vehicles as a result of incomplete combustion of their fuel
global dimming def
the gradual decrease in the amount of sunlight reaching the earth’s surface
what happens when there is not enough oxygen inside an engine
• incomplete combustion occurs • instead of all the carbon in the fuel turning into carbon dioxide, carbon monoxide is also formed
how is carbon monoxide dangerous
• toxic gas, colourless and odourless • red blood cells pick up CO and carry it around blood instead of oxygen • CO takes up sites on haemoglobin in the rbc that usually bond to oxygen
what happens to a victim of carbon monoxide poisoning
• will become starved of oxygen • get drowsy, lose consciousness • die if not removed from source of gas
what does high temperature inside an engine cause
• allows normally unreactive nitrogen gas in the air to react with oxygen • this reaction makes nitrogen oxides
why are nitrogen oxides dangerous
• toxic • can trigger some people’s asthma • also cause acid rain
do diesel engines burn hydrocarbons with bigger or smaller molecules than those in petrol engines
bigger
what happens when large molecules react with oxygen in an engine
• do not burn completely • tiny solid particles containing carbon and unburnt hydrocarbons are produced • particulates get carried into the air • travel into the atmosphere, reflecting sunlight back into space, causing global dimming
what is another reason why particulates are dangerous
scientists think that they may damage cells in our lungs or even cause cancer