Procedure What Am I Doing? Steps 1-7: Preparing the experimental apparatus for testing simple gas laws. Step 8: Heating the gas contained in the apparatus and observing any resulting changes in the system. Step 9: Chilling the gas sample in the apparatus and observing any resulting changes in the system. Steps 11-12: Measuring the volume of water contained in the experimental apparatus after the heating/cooling processes. Step 13: Measuring the volume of the gas flask by measuring the volume of water it can hold. MATERIALS Ring stand Hotplate Clamp 600 mL and/or 1,000 mL beakers (2) 125 mL Erlenmeyer flask 250 mL Erlenmeyer flask 50 ml graduated cylinder Thermometer Wax pencil Tongs or hot mitt Rubber stopper/tubing assembly Steps 14-17: Calculating the values necessary to evaluate the consistency of your data with Boyle's law and repeating the experiment two times. Simple Gas Laws in Action Review the proper technique for using a hot-water bath in Topic 1.4, page 20. Use a 600 mL beaker to prepare a boiling-water bath on a hot plate. Use a separate 600 mL beaker to prepare an ice-water bath. 2 Obtain the rubber stopper and tubing assembly (Fig. 5.4). Fit the stopper into a clean, dry, 125 mL Erlenmeyer flask. We will refer to this flask as the gas flask. 3 On the outside of the gas flask, use a wax pencil to mark the position of the rubber stopper's bottom. 5.4 Rubber stopper and tubing assembly. CHAPTER 5 Matter and Solutions 233 5 5 4 Add about 200 mL of tap water to a 250 mL. Erlenmeyer flask. We will refer to this flask as the water reservoir. 5 Place the open end of the tube assembly from the gas flask into the water contained in the reservoir. Be sure the tube stays submerged in the water throughout the experiment. 6 When your boiling-water bath reaches a steady boil, record the temperatures of both water baths on the data sheet, page 239. 7 Clamp the gas flask securely on a ring stand above the boiling-water bath. 8 Lower the clamp until as much of the gas flask as possible is beneath the surface of the boiling water. At this point, your apparatus should resemble Figure 5.5, and you should immediately see bubbles flowing out of the tube into the reservoir. Record your observations on the data sheet. 9 Allow the gas flask to remain beneath the surface of the boiling water for 3-4 minutes after bubbles cease to emerge from the tube, and then lift the gas flask out of the boiling-water bath. Remove it from the ring stand and quickly lower it into the ice-water bath so that as much of the gas flask as possible is submerged. During this process be careful to ensure that the end of the tube in the reservoir does not emerge from the water. Record any observed changes in the system on the data sheet. 10 When water no longer flows into the gas flask, remove it from the ice-water bath and set it down on the bench top. 11 Use your finger to cover the end of the tube in the water reservoir. Move the end of the tube to a 50 mL graduated cylinder, being careful not to transfer water from your hand during the process. Remove your finger and allow the water in the tube to drain into the graduated cylinder. Lift the gas flask to ensure that all of the water is expelled from the tube. Record the tube volume (VT) on the data sheet. 12 Remove the stopper and use a graduated cylinder to measure the volume of water drawn into the gas flask (V). Record this value on the data sheet. 13 Determine the total volume of the gas flask (VGF) by filling it with water to the line you drew in step 3 and using a graduated cylinder to measure the volume of water added. Record this value on the data sheet. LAB SAFETY The experimental chamber will be very hot! Handle it with tongs or a hot mitt and use caution while transferring it to the ice-water bath! 234 Fisher Scientific Isotemp Exploring General, Organic, & Biochemistry in the Laboratory 5.5 Fully assembled apparatus for gas laws experiment.