1. Prepare the pressure sensor and an air sample for data collection.
2. Turn on the CBL unit and the TI-8X calculator. Press PRGM and select CHEMBIO. Press ENTER, then press ENTER again to go to the CHEM MAIN MENU.
3. Set up the calculator and CBL for a pressure sensor and calibration (in atmospheres).
4. Set up the calculator and CBL for data collection.
5. Collect the pressure versus volume data. It is best for one person to take care of the gas syringe and for another to operate the calculator.
6. Collect MORE DATA from the DATA COLLECTION. Repeat the Step 5 procedure for volumes of 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 mL.
7. STOP AND GRAPH from the DATA COLLECTION menu when you have finished collecting data. Use RIGHT ARROW to examine the data points along the displayed graph of pressure vs. volume. As you move the cursor right or left, the volume (X) and pressure (Y) values of each data point are displayed below the graph. Record the pressure (round to the nearest 0.01 atm) and volume data pairs in your data table.
8. Based on the graph of pressure vs. volume, decide what kind of mathematical relationship you think exists between these two variables, direct or inverse. To see if you made the right choice:
y = a*x^b (y = a*xb)
where x is volume, y is pressure, a is a proportionality constant, and b is the exponent of x (volume) in this equation. Note: The relationship between pressure and volume can be determined from the value and sign of the exponent, b.
1. If the volume is doubled from 5.0 mL to 10.0 mL, what does your data show happens to the pressure? Show the pressure values in your answer.
2. If the volume is halved from 20.0 mL to 10.0 mL, what does your data show happens to the pressure? Show the pressure values in your answer.
3. If the volume is tripled from 5.0 mL to 15.0 mL, what does your data show happened to the pressure? Show the pressure values in your answer.
4. From your answers to the first three questions and the shape of the curve in the plot of pressure versus volume, do you think the relationship between the pressure and volume of a confined gas is direct or inverse? Explain your answer.
5. Based on your data, what would you expect the pressure to be if the volume of the syringe was increased to 40.0 mL. Explain or show work to support your answer.
6. Based on your data, what would you expect the pressure to be if the volume of the syringe was decreased to 2.5 mL.
7. What experimental factors are assumed to be constant in this experiment?
8. One way to determine if a relationship is inverse or direct is to find a proportionality constant, k, from the data. If this relationship is direct, k = P/V. If it is inverse, k = PxV. Based on your answer to Question 4, choose one of these formulas and calculate k for the seven ordered pairs in your data table (divide or multiply the P and V values). Show the answers in the third column of the Data and Calculations table.
9. How constant were the values for k you obtained in Question 8? Good data may show some minor variation, but the values for k should be relatively constant.
10. Using P, V, and k, write an equation representing Boyle's law. Write a verbal statement that correctly expresses Boyle's law.
11. To confirm that an inverse relationship exists between pressure and volume, a graph of pressure vs. reciprocal of volume (1/volume or volume-1) may also be plotted. To do this using your TI-83 calculator, it is necessary to create a new data list, reciprocal of volume, based on your original volume data.
Modified from an experiment by Vernier. Prepared for SMART Center Workshop, July, 1996.
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