213_Lab 3-Fall2021

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University of Illinois, Urbana Champaign *

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213

Subject

Physics

Date

Apr 3, 2024

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pdf

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Uploaded by CoachTigerMaster954

©University of Illinois at Urbana-Champaign Physics 213 Lab 3 Summer 2023 Edition Page 1 of 11 Physics 213 --- Lab # 3 Phase Transitions (Using the new PasPort Sensors) Name: ________________________________________________________ Lab Partner(s): __________________________________________________ (indicate who has plots) _________________________________________________ _________________________________________________ Section: __________________ TA: _____________________________ Lab Date: _______________________________ In this lab, we will carry out a series of measurements involving phase transitions. Key Concepts In This Lab:  Phase transitions  Equilibrium vapor pressure  Latent Heat of Fusion  Latent Heat of Vaporization P: /5 L: /15 T: /20

©University of Illinois at Urbana-Champaign Physics 213 Lab 3 Summer 2023 Edition Page 2 of 11 EXPERIMENT # 1 Vapor Pressure of Water Here we see an illustration of the Boltzmann factor in a common practical example. The idea is to make water at different temperatures boil (T), by reducing its pressure (P) . You’ll find out at which pressure it boils, therefore, what value of water vapor is in equilibrium with liquid water at different temperatures . You’ll reduce pressure just by pulling back on the plunger of a syringe until the water starts to boil, which will make it hard to reduce the pressure any further. Follow the directions carefully. Read the whole procedure before you start to minimize possibility of mistakes. The aim is for you to measure the vapor pressure at two points – one around 45°C and another around 65 to 70°C. For your graph, you’ll use these two measurements along with the vapor pressure for 0°C (which you can assume to be 0.61 kPa) and the vapor pressure for 100°C (which you should know). 1. This experiment uses the same temperature sensor you used in part 1 of this lab and a pressure sensor. Connect and set up the ‘ Type K Temperature sensor ’ to PasPort 1 and the Absolute Pressure sensor to PasPort 2. 2. Open the file: “ P213-Lab3_Experiment 1 - PasPort Sesnsors.cap ” . 3. Click on the “Record” button to continuously display temperature and pressure.

©University of Illinois at Urbana-Champaign Physics 213 Lab 3 Summer 2023 Edition Page 3 of 11 4. Get exactly 1.5 cups of room temperature water in the large Pyrex glass measuring cup (with the handle) from the container at the sink marked “room temperature water for part 1 ”. Heat Pyrex measuring cup of water in one of the microwave ovens for 1 minute. Continue to check temperature until water reaches 45 ° C. 5. Record the temperature in the table below. Fill the syringe containing approximately six Teflon chips with about 15 mL of water. This should fill half of the length of the tube. Hold the syringe with the Luer-lok side up and the hose extended upward. Tap the syringe to get as many of the tiny air bubbles in it to rise to the Luer-lok opening. Hold the tubing over the Pyrex measuring cup; push out the water to around 25 mL to continue process of bubble elimination. 6. Quickly connect the syringe to the Absolute Pressure sensor without letting any air back into the tubing. DO NOT PUSH WATER INTO THE PRESSURE SENSOR! THE WATER WILL BREAK THE PRESSURE SENSOR!! One lab partner will determine when the boiling begins and alert another lab partner who will note the pressure. Lab members will rotate into each task for at least two recordings. 7. Quickly lay the syringe on its side on the lab table. Tap the syringe a bit to spread out the Teflon chips. With one hand holding the syringe securely on the table, steadily pull back the plunger while watching the bubbles form on the Teflon pieces in the syringe. Say “now” at the exact moment that you see a bubble rise off the beads so your partner can simultaneously note the pressure. Record the pressure in the table below. 8. Disconnect tubing from the pressure sensor and push the water from the syringe into a beaker/measuring cup. Rotate with a lab partner repeating steps 4 through 7. If there’s time take a third reading with another lab partner operating the syringe. 9. Next, heat the water to around 67 ° C. Heat Pyrex measuring cup of water in one of the microwave ovens for 1 minute. Continue to check temperature until water reaches 67 ° C. 10. Follow steps 4 through 8 above with the 67 ° C water.

©University of Illinois at Urbana-Champaign Physics 213 Lab 3 Summer 2023 Edition Page 4 of 11 T ( o C) T (K) 1/T (1/K) P (kPa) 100 373 101.3 0 273 0.61 11. Plot p vs. 1/T (absolute T, of course!) on the attached semi-log graph. Draw a straight line that best describes your data. 12. When completed with Experiment 1, delete the data for this run by clicking on the “Delete Last Run” button. 13. Close the file. DO NOT SAVE THE FILE!!! THEORY: It’s a decent approximation to say that the temperature dependence of the equilibrium vapor pressure comes mainly from the Boltzmann factor for the relatively high-energy states of the vapor states. A more precise treatment (the Clausius-Clapeyron equation) gives: p = p 0 exp(-L/kT) or ln(p/p 0 ) = -L/kT or ln(p) = -L/kT + constant where the latent heat L per molecule is almost but not exactly the same as the average extra energy,  E, of a gas molecule above a liquid molecule, and p 0 is a fixed pressure which can be inferred from your data.

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