Christian Smith Dr. Mo. Chehbouni Saturday, September 24, 2016 Identification of Substances by Physical Properties Objective : To familiarize the student with procedures used to evaluate physical properties of substances, and to use these properties to identify an unknown substance. Introduction: When identifying substances sometimes all you have to do is just look at the substance, this is called direct identification. Other times, however, the identity isn’t so obvious. For such cases there needs to be another method. Substances have a unique set characteristics (called properties), since these properties are unique to each individual substance they can be used for the purpose of identification. In this experiment we will become acquainted with the different physical properties (i.e. properties that can be observed without altering the composition of the substance) of substances and how these properties identify the substance. The physical properties that we will be using are: the melting point, boiling point, solubility, density, viscosity, and refractive index. In step A we will learn about the solubility and how to relate it to a substance. Step B will deal with Density and how it can be used to identify a substance. Step C will teach about the melting point of an unknown, and finally, step D will tackle the property of the boiling point. By the end of this experiment the student will have a basic knowledge of how to determine the physical properties of an unknown substance, and in turn be able to derive the identity of the substance from these properties. Pre-lab: 2. A 1.22 g sample of an unknown has a volume of 1.73 cm3. What is the density of theunknown? 5. What would be the boiling point of hexane at 670 mm Hg? 8. When water and bromoform are mixed, two layers form. Is the bottom layer water orbromoform?
9. What solvent would you use to determine the density of zinc chloride?
You've reached the end of your free preview.
Want to read all 8 pages?