Experiment: Evaporation and Intermolecular Attractions, Lab Reports of Physics

Download Experiment: Evaporation and Intermolecular Attractions and more Lab Reports Physics in PDF only on Docsity! Experiment: Evaporation and Intermolecular Attractions Purpose The purpose of this lab activity is to study temperature changes caused by the evaporation of several liquids and relate the temperature changes to the strength of the forces of attraction between molecules of the liquid. Introduction When temperature sensors are removed from a liquid, evaporation occurs. Evaporation is an endothermic process that results in a temperature decrease for the surrounding air. The magnitude of a temperature decrease is related to the strength of the intermolecular forces of attraction in that the greater the decrease in temperature the greater the attractive force strength. You will encounter two types of organic compounds called “hydrocarbons” – alkanes and alcohols. The two alkanes used in this experiment are pentane, C5H12, and hexane C6H14. In addition to carbon and hydrogen atoms, alcohols also contain the –OH functional group. Methanol, CH3OH, and ethanol, C2H5OH, are two of the alcohols that will be used in this experiment. The molecular structure of alkanes and alcohols will be examined for the presence and relative strength of the two intermolecular forces – hydrogen bonding and dispersion forces. Pre-Lab Exercises You will need to complete the title, purpose, storyboard of the procedures, develop a prelab table for the lab (*see instructions and example below) and, copy the data table below into your lab book as a prelab. As in the past, if the pre-lab assignment is not completed you will not be permitted to participate in the lab. Complete a pre-lab table before beginning the experiment. The name and formula are given for each compound and should be given in the first column on your table. Draw a structural formula for a molecule of each compound and include that in the second column. Determine the molar mass of each compound and put that in the third column. Next, examine each molecule for the presence of hydrogen bonding. Before hydrogen bonding can occur, a hydrogen atom must be bonded directly to an N (nitrogen), O (oxygen), or F (fluorine) atom within the molecule. Indicate whether or not each molecule has hydrogen-bonding capability in the pre-lab table in the forth column. Prelab Table: Substance Formula Structural Formula Molecular weight Hydrogen Bonding? Ethanol C2H5OH 1-propanol C3H7OH 1-butanol C4H9OH Methanol CH3OH Pentane C5H12 n-hexane C6H14 Data/prediction tables: Substance Ti (C) Tf (C) T (C) Ethanol 1-propanol Predicted T Explanation 1-butanol Methanol Pentane n-hexane