Lab Gas Properties - Phys 242c 2020 - SFSU ✓ Solved

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Lab Gas Properties Phys 242c 2020 Sfsu Adapted From Copyright

In this lab we will study several macroscopic quantities that can be used to describe a gas and explore the relationships among these quantities using a simulation from the PhET team. The simulation can be run in a browser. If you have issues with the simulation, try using another browser. If you are unable to run the simulation, your TA will provide you with remote assistance. When you run the simulation, choose the “Ideal” option.

At the very bottom of the screen, you will see the other options for the simulation, including a home button, “Ideal,” “Explore,” “Energy,” and “Diffusion.” If you accidentally navigate to another area, you can return to the Ideal option by clicking the button. The simulation shows a preset volume. In its initial configuration, the box is empty. On the right side of the screen, there is a menu labelled “Particles.” By expanding this menu, you can choose to add heavy or light particles. These particles will enter the volume at a temperature of 300 K in the initial setup.

Once there are particles in the box, the temperature and pressure in the box can be read off the scales on the right corner of the box. The units can be changed for these values. To adjust the temperature of the particles in the box, move and hold the slider bar below the box. On the left, there is a handle to change the size of the box. There is also a lever at the top of the box that can be lifted to open the box, allowing particles to escape. Particles can also be removed from the box by reducing the number of particles in the “Particles” menu. Finally, to refresh the simulation to the initial point, click the arrow in the bottom right.

Lab: Gas Properties Phys 242. I. Volume A. Refresh the simulation so that you begin with an empty box. Add 100 heavy particles to the box. Which of the quantities in the ideal gas law, P, V, N, kB, or T, does “100 heavy particles” describe? B. Select the width option in the right panel. This will put a scale bar on the bottom of the box. Assuming the box is a cube, what is the volume of the box? C. Keep the box closed and use the handle on the side to make the box smaller. Did the volume of gas change? Explain. Did the number of molecules of gas enclosed in the system change? Explain.

D. Consider the following statement made by a student in an introductory physics class. “As I pushed the handle inward, no air entered or left the system, so the volume did not change.” Explain what is incorrect about this student’s statement. II. Measuring the Pressure A. Refresh the simulation. What is the pressure in the box when 100 heavy particles have been added? Note that this value fluctuates, so you will have to estimate a value. B. Atmospheric pressure is about 101 kPa (or 1 atm). How does the reading you obtained compare to atmospheric pressure?

C. Suppose you were to change the volume of the box. Predict whether the pressure reading would be greater than, less than or equal to the value you measured in Part A if the volume were decreased? D. Check your predictions by changing the volume of the box. Decrease the volume of the box. Is the pressure reading greater than, less than or equal to the value you measured in Part A? Increase the volume of the box. Is the pressure reading greater than, less than or equal to the value you measured in Part A?

E. Now, for each volume in the table at right, record the value of the pressure of the gas. F. Once you have obtained your entire data set, create a graph showing the relationship between the pressure and the volume using your data. G. As the volume increases, does the pressure increase, decrease, or remain the same? H. Does the pressure change linearly with the volume? Explain how you know. I. Is your data consistent with the Ideal Gas Law? Explain.

III. Forces exerted by a gas. Refresh the simulation and add 100 heavy particles to the box. A. Draw a free-body diagram for the top of the box (i.e., draw vectors representing the forces exerted on the box). For each force, indicate the type of force, and identify the object on which the force is exerted and the object exerting the force. B. Is your free-body diagram consistent with the fact that a gas can only push (and not pull) on other objects? C. Does your free-body diagram include any forces exerted by the air outside the box?

D. Predict what will happen to the net force if you increase the pressure inside of the box. E. Test your prediction while keeping the volume constant. (Hint: think about how you can increase the pressure inside the box.) If you increase the pressure, does the top of the box move? Explain your findings. Try increasing the pressure as high as you can.

IV. Changing the temperature with the volume free to change. Reset the simulation. With 100 heavy particles in the box and a width of 10 nm, select the “Pressure→V” option in the right panel. This will allow the box to expand. Now imagine that you will heat the system. A. Predict whether the following quantities would increase, decrease, or remain the same. Explain your reasoning. The temperature of the gas in the system, the pressure of the gas in the system, and the volume of the gas in the system. In the process above, which of the quantities P, V, n, and T are held constant and which are allowed to change? Sketch the process above on a PV diagram.

B. Check your predictions by heating the bottom of the box. 1. Heat the box and record the resulting T, P, and V. 2. Repeat your measurement for three additional temperatures. C. Examine the PV diagram you drew for this experiment and check that your prediction is consistent with the data you recorded. Resolve any inconsistencies. D. Consider the statement made by a student. "According to the ideal gas law, the pressure is proportional to the temperature. That means that whenever I increase the temperature of the gas, the pressure must go up." Explain what is incorrect about this student’s statement.

E. Plot all four measurements of the volume of the gas in the system versus the temperature using your data from part B above. The four points should lie nearly along a straight line. Draw a line that is a good approximation to that line. Use your graph to estimate the temperature at which the volume of the air in the system would be zero. The process you carried out in this experiment is commonly referred to as an isobaric process.

V. Changing the temperature with the volume fixed. Reset the simulation and add 100 heavy particles to the box. Now select the “Volume” option in the left panel. Imagine that we will again heat the box. A. Predict whether the following quantities would increase, decrease, or remain the same. In each case, explain your reasoning. The temperature of the gas in the system, the volume of the gas in the system, and the pressure of the gas in the system.

In this process, which of the quantities P, V, n, and T are held constant and which are allowed to change? Sketch the process above on a PV Diagram. B. Check your predictions by heating the box. 1. Heat the box and record the resulting T, P, and V. 2. Repeat your measurement for three additional temperatures. a. Does the pressure change? b. Plot your measurements of the (absolute) pressure of the gas in the system versus the temperature.

3. The points should lie nearly along a straight line. Draw a line that is a good approximation to that line. Use your graph to estimate the temperature at which the pressure of the air in the system would be zero. This temperature is referred to as absolute zero, or 0 Kelvin. How do your results compare? The process you carried out in this experiment is commonly referred to as an isovolumetric process.

Paper For Above Instructions

The study of gas properties reveals essential insights into the behavior of gases under various conditions. This laboratory exercise focuses on the Ideal Gas Law and the phenomena associated with changes in volume, pressure, and temperature. By employing the PhET simulation, students explore the fundamental relationships between these quantities through hands-on experimentation.

Initially, students create an environment within the simulation by adding 100 heavy particles at 300 K. The first step is to reflect on what the introduction of these particles signifies concerning the Ideal Gas Law (PV = nRT). Here, 'N' corresponds to the number of particles added. This fundamental relationship lays the groundwork for subsequent investigative steps.

The first calculations examine the volume of the box when all particles are added. Given the box is assumed to be a cube, if each side measures 'x' nanometers, then the volume, V, is expressed as V = x³. This volume constitutes the space entities occupy at standard conditions, where pressure and temperature can be manipulated. It is crucial to note that reducing the box's size affects the gas's volume but does not alter the number of molecules within it. Therefore, while the statement by the student that "no air entered or left the system" is technically correct, it neglects the fact that reducing volume increases the gas pressure, illustrating the principles of gas dynamics and confinement.

Understanding pressure requires statistical interpretation. When measuring pressure after adding particles, the oscillating nature of the pressure reading reflects gas behavior under confined conditions. Typical observations indicate that the pressure rises when the box's volume is constricted due to the gas particles colliding more frequently with the walls. Conversely, increasing the volume results in decreased pressure, congruent with Boyle's Law, indicating an inverse relationship between volume and pressure (Boyle, 1662).

Incorporating varied volumes expands the dataset. It is necessary to document the readings accurately and produce a graphical representation correlating pressure versus volume. The graphical interpretation should exhibit a downward slope, indicating that as volume increases, pressure decreases—a manifestation of Boyle’s Law’s graphical characteristics.

As part of the experiment on forces exerted by the gas, students are asked to visualize and draw free-body diagrams. This understanding empowers them to recognize that gases can exert force solely through collision, as they push against the surfaces but cannot pull objects toward themselves. This concept reinforces the uniqueness of gas dynamics where pressure within the box is contingent upon the stored energy and the activity level of individual particles, leading to higher pressures with energized states.

Subsequently, temperature becomes a focal element when discussing the gas's behavior under heat. An understanding of how heating affects pressure and volume can clarify misconceptions. When increasing temperature while allowing volume to expand, a predictable decrease in pressure occurs as pressure only remains constant at fixed volumes. This adaptive behavior aligns with Charles's Law, which states that gas volume increases with temperature at constant pressure (Charles, 1802). Illustrating these relationships through PV diagrams enhances comprehension of theoretical principles in real-life applications.

The experiment’s illustrations of isobaric and isovolumetric processes deepen comprehension of thermodynamic principles. During an isobaric expansion, the gas occupies more space as it heats while simultaneously building pressure. Conversely, in an isovolumetric process, heating causes increases in pressure but requires volume to remain constant, highlighting the behaviors exhibited by gases as they respond to temperature change.

Finally, students are tasked with exploring absolute zero and the implications of achieving a temperature of -273.15°C. Understanding this concept leads to discussions about the kinetic molecular theory and the energy inherent in particles at absolute zero state and the nature of gases under extreme conditions. Establishing connections between experimental data and theoretical principles enriches the understanding of physical science, equipping students for future scientific endeavors.

In summary, this laboratory investigation into gas properties provides a fundamental understanding of the Ideal Gas Law. Through interactive simulations, students gain practical experience in measuring properties, analyzing behaviors, and applying theoretical principles in an experimental setting. Engaging with these concepts cultivates an innate understanding of the natural laws governing gas behavior and helps prepare students for advanced studies in physics and engineering.

References

• Boyle, R. (1662). New Experiments Physico-Mechanical, Touching the Spring of the Air and its Effects. Oxford: Henry Hall.
• Charles, J. (1802). Sur l'Équilibre des Fluides. Paris: Dufour.
• Ideal Gas Law. (2020). Retrieved from PhET Simulations. [URL]
• Engel, T., & Reid, P. (2017). Thermodynamics, Statistical Thermodynamics, and Kinetics. Pearson.
• Atkins, P. W., & de Paula, J. (2014). Elements of Physical Chemistry. Oxford University Press.
• Rosenberg, A., & Rosenberg, B. (2001). Physics Laboratory Experiments. Boston: Cengage.
• Thermodynamics. (n.d.). In Encyclopedia Britannica. Retrieved from [URL]
• Mills, A. (2015). Gases and Their Properties. New York: Wiley.
• AEROSOL Therapy: Physical Chemistry of Gases. (n.d.). Retrieved from [URL]
• Reiss, H. (1993). Gases: Kinetic Theory and Thermodynamics. Oxford University Press.

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