Lab: Ideal Gas Law Objectives • Use the ideal gas law to understand the relationship of pressure, temperature, and volume • Conduct experiments within a closed system • Use lab procedures and equipment to conduct an experiment Introduction Have you ever been in an airplane or taken a trip through the mountains and felt the pressure change in your ears? The middle ear is a hollow space. If the atmosphere or conditions outside your ear are different than those in the middle ear, you will feel a pressure difference. Yawning or chewing will open your Eustachian tubes and relieve pressure. The air in the atmosphere is a complex mixture of gases and other particulates. Gases, like other substances, react to external changes, such as pressure and temperature. The relationship between temperature, pressure, and volume of a gas is best explained by the “ideal gas law.” The formula for the ideal gas law demonstrates this relationship: pV = nRT In the formula, p represents the absolute Figure 1: Divers preparing to search the shipwreck of the Lusitania. The diver on the right is wearing a standard diving suit. The diver on the left is wearing an atmospheric pressure diving suit or ADP. Divers in an ambient suit will feel the effects of changes in pressure while the ADP keeps the pressure constant as in a high altitude airplane. pressure of the gas, V is the volume, n is the amount of the substance, R represents the gas constant ( 0.08205 L atm /K mol ), and T is the absolute temperature. © KC Distance Learning Understanding the relationship between the pressure, temperature, and volume of a gas is important in many different systems. The ideal gas law and other gas laws help us understand the performance of gases in the atmosphere, the compre ssion of gases in an engine, the affects of pressure on gases in the blood, the control of air pressure in an airplane, fluid dynamics in wind turbines, different functions of rockets and space science technology, and countless other applications. Gases are all around you and affect every aspect of your life. The odor s you encounter, the air you breathe, even your ability to move your muscles are all affected by changes in gases. Figure 2: Here we see a U.S. Navy diver testing a new ADP suit. Divers wearin g these suits can perform submarine rescue activities and work on oil rigs. In 2006 a diver wea ring an ADP suit descended to a depth of 2000 feet where the pressure is 60 times greater than at sea level. Figure 3: A sonic boom cloud created by a Navy F-18 Hornet. The clo ud, technically referred to as a Prandtl-Glauert singularity, can be seen when water vapor condenses because of a sud den drop in air pressure. Usually seen with supersonic jets and rockets. As you’ll discover in this lab, gases can act differently under different conditions of pressure, temperature and volume. Extreme changes in pressure, temperature or volume can cause gases to act much like a liquid or even a solid. Figure 4: Blue jets of oxygen are ejected from the Cygnus Loop supernova 15,000 years ago and are traveling at o ver 3 million miles per hour. The Cynus Loop supernova is 2600 light years from Earth. © KC Distance Learning Figure 5: A Beluga whale blowing a b ubble-ring or air-ring. Dolphins, humans, and other mammals can blow bubble-rings under water. Pre-lab Questions 1. List and describe each of the parts of the ideal gas law. Be sure to include the units for each part. 2. What happens to the molecules in a gas when the temperature of a gas is raised? 3. What are some examples of gases you encountered today? © KC Distance Learning Experiment: The Ideal Gas Law In this experiment, you will be working with a simulated lab. Study the screen shot of the simulator and pay close attention to the highlighted controls. These controls, along with others specified in the lab procedures will assist you in successfully completing this experiment. As you conduct each portion of the experiment, be sure to write down your observations. NOTE: If your experiment gets out of control, you can start over by clicking the reset button located on the right control panel. Materials PhET Lab: Balloons and Buoyancy © KC Distance Learning Procedure – Part 1: Pressure, Temperature, and Volume • At the top of the screen, click the “Gas Properties” menu tab. • Make sure the “None” property is selected for the Constant Parameter located at the top of the right control panel. STEP 1: Raise the pump handle as far as it will reach and make one full downstroke. STEP 2: Record the following data: temperature, pressure, amount of gas in chamber, volume of chamber, and notes. Calculate the volume by turning on the ruler, using the “Measurement Tools” button in the control panel and measuring the length of the pressure chamber (the height and depth will remain the same at 5.6 nanometers). Ideal Gas Laws – Gas Properties Amount STEP (heavy species) 2 95 Notes Amount Temp. Pressure 0 300K 0.50 atm (light species) Volume (5.6nm x 5.6nm x 6.8 nm) 213.3 nm3 The particles are moving and colliding with each other causing minor variations in the pressure within the chamber. (5.6nm x 5.6nm x 3 nm) nm3 Notes (5.6nm x 5.6nm x 4 nm) nm3 Notes (5.6nm x 5.6nm x 5 nm3 © KC Distance Learning nm) Notes (5.6nm x 5.6nm x 6 nm) nm3 Notes STEP 3: Observe any changes that occur when you make another full down-stroke on the handle of the pump containing the heavy species of gas. STEP 4: Observe any changes that occur when you use the volume slider on the left hand side of the pressure chamber to reduce the width of the chamber to 5.6 nanometers. STEP 5: Observe any changes that occur when you use the heat control (located under the pressure chamber) to add heat to the system. STEP 6: Observe any changes that occur when you use the heat control (located under the pressure chamber) to remove heat from the system. STEP 7: Reset the simulator. Procedure – Part 2: Design Your Own Experiment 1. Use the space and data table provided below to create your own experiment with the gas laws. © KC Distance Learning Ideal Gas Laws – Gas Properties STEP Amount (heavy species) Amount (light species) Temp. Pressure Volume (5.6nm x 5.6nm x 2 nm) nm3 Notes (5.6nm x 5.6nm x 3 nm) nm3 Notes (5.6nm x 5.6nm x 4 nm) nm3 Notes (5.6nm x 5.6nm x 5 nm) nm3 Notes (5.6nm x 5.6nm x 6 nm3 Notes © KC Distance Learning nm) Post-lab Questions 1. Use the ideal gas law formula to show the effects on temperature and pressure when the volume of the pressure chamber was decreased. 2. What affect would lowering the temperature of the gas in a chamber have on a helium balloon trapped inside the chamber? 3. Describe the discovery you made when you conducted your own gas experiment. © KC Distance Learning
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