5.6 Petrol 5.6.1 Petrol Engines LO: I understand how a petrol engine works

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<ul><li> Slide 1 </li> <li> 5.6 Petrol 5.6.1 Petrol Engines LO: I understand how a petrol engine works. </li> <li> Slide 2 </li> <li> Burning petrol: Petrol vapour and air are mixed and compressed. The mixture is ignited by a spark. Pollution: Inefficient burning produces carbon monoxide. The spark produces nitrogen oxides. LO: I understand how a petrol engine works. </li> <li> Slide 3 </li> <li> 5.6.2 Octane Number LO: I understand what is meant by the octane number of a fuel. </li> <li> Slide 4 </li> <li> The standard for the quality of a petrol fuel is measured against iso-octane: The higher the number the more smoothly the petrol burns. 2,2,4-trimethylpentane Iso-octane burns smoothly and is given an octane number of 100. LO: I understand what is meant by the octane number of a fuel. </li> <li> Slide 5 </li> <li> The octane number can be increased by: decreasing the carbon chain LO: I understand what is meant by the octane number of a fuel. increasing the branching using aromatics If the octane number is too low the fuel will auto ignite at the wrong point in the engine cycle. This can damage the engine. </li> <li> Slide 6 </li> <li> 5.6.3 Petrol Production LO: I understand how petrol is made. </li> <li> Slide 7 </li> <li> Petrol is made from 3 fractions of crude oil: Reforming the naphtha fraction: LO: I understand how petrol is made. changes the shape of the molecules without changing the number of carbon atoms </li> <li> Slide 8 </li> <li> Hydrocracking the residue fraction: Also, the more volatile a fuel is the better it burns. LO: I understand how petrol is made. Splits up the molecules into smaller ones Butane and pentane is added to fuel in winter months to make it vaporise more easily. </li> </ul>

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