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Richard F. Daley and Sally J. Daley Organic Chemistry Chapter 4 Physical Properties of Organic Compounds 4.1 Phases of Matter 175 Sidebar - Liquid Crystals 178 4.2 Melting Points 179 4.3 Boiling Points 183 4.4 Solubility 190 Sidebar - Surfactants 194 4.5 Density 197 Key Ideas from Chapter 4 199 Organic Chemistry - Ch 4 173 Daley & Daley Copyright 1996-2005 by Richard F. Daley & Sally J. Daley All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the copyright holder. 5 July 2005 Organic Chemistry - Ch 4 174 Daley & Daley Chapter 4 Physical Properties of Organic Compounds Chapter Outline 4.1 Phases of Matter A review of the common phases of matter: solid, liquid, and gas 4.2 Melting and Freezing Points Factors affecting the melting and freezing points of a compound 4.3 Boiling Points Factors affecting the boiling point of a compound 4.4 Solubility Why a compound is soluble in a given solvent 4.5 Density Factors affecting the density of a compound Objectives Understand what the terms solid , liquid , and gas mean at the molecular level Know how the symmetry and conformation of an organic structure affect its melting point Understand how a functional group affects the melting point of a compound Know how structure and functional groups affect the boiling point of a compound Recognize the molecular features that affect the solubility of a compound Know what molecular features affect the density of a compound Be able to rank compounds in order based on the physical properties discussed 5 July 2005 Organic Chemistry - Ch 4 175 Daley & Daley Contrariwise, continued Tweedledee, if it was so, it might be; and if it were so, it would be: but as it isn't, it ain't. That's logic. Lewis Carroll T he physical properties of a compound include such things as its color, odor, refractive index, density, solubility, melting point, and boiling point. The exact values of the physical properties of a compound depend on its molecular structure. All the physical properties of a compound correlate with its molecular structure. Although chemists cannot examine the structure of a compound and predict the exact values for these physical properties, they can look at two compounds with similar structures and determine which has the higher melting or boiling point. By knowing the structure of a compound, a chemist can also choose a better solvent to extract or recrystallize the compound. Knowledge of physical propertiessuch as solubilities, melting or boiling points, and densitywill assist you in making judgments about the practical aspects of the isolation and purification of new molecules. This translates into doing better laboratory work. ... View Full Document

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