Evaporation Theory

The purpose of this lab was to use what we know and have learned about evaporation, the molecular-kinetic theory of matter, and intermolecular forces to determine the relative strength of the intermolecular forces that exist between the molecules in six different types of liquids. This is important because chemists often need to rely on their understanding of intermolecular interactions to explain the bulk properties of matter. It will also help us understand the reason for many natural occurrences, such as the water cycle or evaporative cooling, that have many practical applications for everyday life. The guiding question for this lab was which of the substances has the strongest intermolecular forces. Our claim was that Isopropyl alcohol

Which state the substance is is determined by different properties at room temperature. Boiling or vaporization is the process by which a substance changes from a liquid to a gas. Evaporation is vaporization that occurs at the surface of a liquid. According to the molecular-kinetic theory of matter, the molecules in a liquid are always moving but are attracted to other molecules by different types of intermolecular forces. Some of the molecules will have enough kinetic energy to disrupt the intermolecular forces that hold it near the other molecules in the liquid. These molecules, as a result, will break away from the surface of the liquid. When this happens, the average kinetic energy of the remaining molecules in the liquid decreases. The temperature of a liquid decreases as it evaporates. Many factors can influence the evaporation rate of a liquid. One of these factors is the type of intermolecular forces that exist between the molecules in that liquid. For example, a liquid with strong intermolecular forces will evaporate slowly because it takes more energy to break the bonds in the

This means that it has very strong bonds which we assume to be hydrogen bonds. They are the strongest of the three types of intermolecular force bonds. Acetone had a very fast rate of evaporation which means it had very weak intermolecular forces. Methanol had a mostly neutral rate of evaporation and its intermolecular forces were neither weak nor strong. Heptane has the weakest intermolecular forces because its rate of evaporation was the fastest out of all the substances. This means it had very weak bonds which we can infer from this that it probably is made up of dipole-dipole interactions. Hexane also has very strong intermolecular forces but because the rate of evaporation was still faster than the Isopropyl alcohol it means it doesn’t have the strongest intermolecular forces. Lastly, Ethyl alcohol’s intermolecular forces show that they were probably made up of mostly dispersion forces because of its neutral rate of evaporation. This lab had us learn about temperature changes due to evaporation, intermolecular forces, kinetic molecular theory, and the different types of bonds that hold the molecules together. It helped us gain a better understanding of molecules and bonds in substances as well as how kinetic energy can affect the results of different occurrences. This lab was fun and relatively simple to understand and conduct.