The purpose of this experiment is to determine how intermolecular forces affect physical properties. There are three interactions, which affect the physical properties of substances and solutions. These are dipole-dipole, ion-dipole, and London type dispersion forces, which are collectively known as van der Waals interactions.

The dipole-dipole forces exist between two dipole molecules, such as water molecules and ethanol molecules.  Ion-dipole forces exist between ions and polar molecules. The London dispersion forces are attractions between and instantaneous dipole and an induced dipole. These are present in all molecules, whether they are polar or nonpolar. The bond strength between molecules is determined by the melting point, boiling point, and vapor pressure of a substance at a given temperature.

In this experiment we will graph the pressure versus temperature of ethanol and acetone. We will also calculate the heat of vaporization of both substances from the slope recorded from the data collection system. In the experiment we will use a 1500mL beaker with ¾ full of water. Then we will obtain a 250mL Erlenmeyer flask and place it on a ring stand with a clamp and submerge it in the 1500mL beaker all the way to the rubber stopper. Then by connecting the absolute pressure sensor to the data collection system we will be able to record the pressure. The temperature sensor will then be inserted into the rubber stopper on top of the 250mL flask to record the temperature. The beaker will be place on a hot plate and heated to 80*C then we will transfer 50mL of ethanol into the Erlenmeyer flask and after a few minutes we will begin recording our data until the temperature drops to 30*C. We will repeat the process except this time we will use the acetone solution.

I predict that we will see a decrease in pressure as the temperature drops because the molecules of the solutions will begin to slow down as the temperature is decreasing. The decrease will be rapid due to the properties of ethanol and acetone so the graphs will curve down then they will eventually even out, as the temperature remains constant and the pressure. Since ethanol has a high boiling point because of the hydrogen bonds, we will see that the curve will begin at a higher temperature then drop dramatically. Acetone on the other hand has a low boiling point so its line curve will begin at a lower temperature then drop dramatically.