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  Home > JCE Print > Journal of Chemical Education > Issues > 2007  > October  >
In the Laboratory
Freezing Point of Milk: A Natural Way To Understand Colligative Properties
Mercedes Novo, Belén Reija, and Wajih Al-Soufi
Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, E-27002 Lugo, Spain
Cover
October 2007
Vol. 84 No. 10
p. 1673

Abstract
A laboratory experiment is presented in which the freezing point depression is analyzed using milk as solution. The nature of milk as a mixture of different solutes makes it a suitable probe to learn about colligative properties. The first part of the experiment illustrates the analytical use of freezing point measurements to control milk quality, regarding adulteration by addition of water and lactic fermentation. The second part deals with molecular weight determination from freezing point depression data, using powdered milk as solute. The effective molar masses of whole milk and skim milk are determined and compared.
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Citation
Novo, Mercedes; Reija, Belén; Al-Soufi, Wajih. J. Chem. Educ. 2007, 84, 1673.
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Keywords
Consumer Chemistry; First-Year Undergraduate / General; Food Science; Hands-On Learning / Manipulatives; High School / Introductory Chemistry; Laboratory Instruction; Natural Products; Phases / Phase Transitions / Diagrams; Physical Chemistry; Second-Year Undergraduate; Solutions / Solvents
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History
Created:
Last Updated:
8/20/2007
9/7/2007
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Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.
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