Physical Properties

Introduction

Physical properties are used a lot in chemistry to determine what the substance is or to make sure that two substances are the same. For example, if someone wanted to figure out if their gold was pure gold and not mixed with other metals, they could test some of its physical properties to determine if it is truly pure gold. This experiment is designed to build skills needed to determine physical properties of substances to identify an unknown.

The goals of this experiment was to determine how density is related to mass and volume by conducting an experiment that provides the volume and mass data of isopropyl alcohol and graphically determining the density. Density and solubility of a substance is temperature dependent so an additional assignment was given to determine the density of water at cold, room, and hot temperatures as well as ice. There was also assigned an unknown solid and an unknown liquid. In order to indentify the unknowns, we designed an experiment to determine some of the physical properties.

Experimental

Materials: Unknown liquid Unknown Solid Lab drawer equipment (graded cylinder, beaker, stirring stick, etc.) Laboratory equipment (balance, thermometer, hot plates, etc.) Water (solid and liquid) 2-propanol (isopropyl alcohol) Cyclohexane (for solubility tests)

To graphically determine the density of 2-propanol we needed to find different measurements of the volume and masses of the known liquid. We started off by weighing the mass of a 50ml graded cylinder. Then we filled the cylinder with 2ml of the alcohol. We determined the mass, of 2ml of the alcohol by subtracting the weight of the empty graded cylinder by the cylinder and the solution. We repeated this experiment with 4ml, 6ml, 8ml, and 10ml of 2-propanol. We then made a chart of the data.

For the second goal we weighed a 100ml empty cylinder. We then filled the cylinder with 50ml of room temperature water. We weighed it again and then subtracted the mass of the empty cylinder with the mass of the cylinder and the solution. We used the formula d= m/v to determine the density of the room temperature water. Determining the density of the hot and cold water was a little more difficult. We first found the density of cold water. We gathered a beaker of water and surrounded it with ice. We put a thermometer into the beaker and waited until the water was around 20 degrees lower than room temperature. We weighed the mass of an empty 100ml cylinder and then filled it with 50ml of the cold water. We weighed the mass of the cylinder and the solution and then took the temperature. We found the density the same way as the room temperature water. For the hot water we heated up a beaker of water on a hot plate. We waited till the water was around 20 degrees above room temperature before we added 50ml into the graded cylinder. We repeated the same procedure as before. We gathered an amount of ice and weighed it on a scale. To find the volume we took the same amount of ice and dropped it into 20ml of cooled ethyl alcohol to see how much it displaced. Calculating the density was the same as before.

To determine the unknown liquid we first found its boiling point. We heated up the content in a beaker of water with a test tube and a capillary tube of the unknown. Once the liquid in the test tube started to bubble we turned off the heat and when the liquid went into the capillary tube we took the temperature, which determined the boiling point. We then found the density of the unknown liquid. For the solid we found the melting point from a special devise that was provided in the lab that would melt a small amount of the solid in a capillary tube. We then found if the solid was soluble in water or Cyclohexane.