From Atoms to Materials

small molecular size large boiling point high low fraction 餾份 fractional distillation 分餾法 • Crude oil is a mixture of many compounds. Most of these compounds are hydrocarbons. • Hydrocarbons are compounds made up of the elements hydrogen and carbon only. They exist as molecules. • In general, the larger a hydrocarbon’s molecular size, the higher its boiling point. Fig. 13.31  General relation between molecular sizes and boiling points of hydrocarbons refining 提煉 How to separate hydrocarbons in crude oil? Crude oil is a mixture of many hydrocarbons, which may have different uses. To use crude oil effectively, we first need to separate crude oil into different components. This process is called refining*. As we have just seen, in general, a hydrocarbon of larger molecular size has a higher boiling point. By making use of the boiling point differences, we can separate the hydrocarbons in crude oil into fractions of different boiling point ranges. B The process of separating crude oil into fractions is known as fractional distillation . Let’s see how it is done. 13 From Atoms to Materials 83 © United Prime Educational Publishing (HK) Limited 2024 All rights reserved; no part of this publication may be reproduced, photocopied, recorded or otherwise, without the prior written permission of the Publisher. Sample