# Lussac's Law

## What are we doing?

Studying the relationship between the temperature of a gas sample and the pressure it exerts.

Determining mathematical relationship between pressure and absolute temperature of a confined gas.

Finding a value for absolute zero on the Celsius temperature scale.

In order to prepare yourself, You'll probably need these items.

Computer with Vernier Software

Logger Pro

Vernier Gas Pressure Sensor

Vernier Temperature Probe

Plastic Tubing with two connectors

Ring stand

Utility Clamp

Hot Plate

Four One-liter beakers

Gloves or Cloth

## Procedure

1. Put on goggles.

2. Prepare an ice-water bath.

4. Prepare a room water bath.

5. Prepare a hot water bath.

6. Prepare the Temperature Probe and Gas Pressure Sensor for data collection.

a.Plug the Gas Pressure Sensor into CH1 and the Temperature Probe into CH2 of the computer interface.

b.Obtain a rubber-stopper assembly with a piece of heavy-wall plastic tubing connected to one of its two valves. Attach the connector at the free end of the plastic tubing to the open stem of the Gas Pressure Sensor with a clockwise turn. Leave its two-way valve on the rubber stopper open until Step 9.

c.Insert the rubber-stopper assembly into a 125 mL Erlenmeyer flask. Important: Twist the stopper into the neck of the flask to ensure a tight fit.

d.Close the 2-way valve above the rubber stopper—do this by turning the valve handle so it is perpendicular with the valve stem. The air sample to be studied is now confined in the flask.

7. Prepare the computer for data collection by opening the file “07 Pressure-Temperature” from the Chemistry with Computers folder of LoggerPro.

8. Click the collect button to begin data collection.

9. Collect pressure vs. temperature data for your gas sample:

a.Place the flask into the ice-water bath. Make sure the entire flask is covered. Stir.

b.Place the temperature probe into the ice-water bath.

c.When the pressure and temperature readings displayed in the meter stabilize, click the keep button . You have now saved the first pressure-temperature data pair.

10. Repeat the Step-9 procedure using the room-temperature bath.

11. Repeat the Step-9 procedure using the hot-water bath.

12. Click when you have finished collecting data. Turn off the hot plate. Record the pressure and temperature values in your data table, or, if directed by your instructor, print a copy of the table.

13. Examine your graph of pressure vs. temperature (°C). In order to determine if the relationship between pressure and temperature is direct or inverse, you must use an absolute temperature scale; that is, a temperature scale whose 0° point corresponds to absolute zero. We will use the Kelvin absolute temperature scale. Instead of manually adding 273 to each of the Celsius temperatures to obtain Kelvin values, you can create a new data column for Kelvin temperature.

a.Choose New Calculated Column from the Data menu.

b.Enter “Temp Kelvin” as the Name, “T Kelvin” as the Short Name, and “K” as the Unit. Enter the correct formula for the column into the Equation edit box. Type in “273+”. Then select “Temperature” from the Variables list. In the Equation edit box, you should now see displayed: 273+“Temperature”. Click the done button.

c. Click on the horizontal axis label and select “Temp Kelvin” to be displayed on the horizontal axis.

14. Decide if your graph of pressure vs. temperature (K) represents a direct or inverse relationship:

a.Click the Curve Fit button, .

b.Choose your mathematical relationship from the list at the lower left. If you think the relationship is linear (or direct), use Linear. If you think the relationship represents a power, use Power. Click the try fit button.

c.A best-fit curve will be displayed on the graph. If you made the correct choice, the curve should match up well with the points. If the curve does not match up well, try a different mathematical function and click the try fit button again. When the curve has a good fit with the data points, then click the okay button.

d. Autoscale both axes from zero by double-clicking in the center of the graph to view Graph Options. Click the Axis Options tab, and select Autoscale from 0 for both axes.

15. Print a copy of the graph of pressure vs. temperature (K). The regression line should still be displayed on the graph. Enter your name(s) and the number of copies you want to print.

## The Data

The graph below shows the data revealed in this lab that answered the following questions.

1.In order to perform this experiment, volume and mass were two variables that were kept constant.

3. Based on the data and graph obtained for this experiment, the relationship between gas pressure and temperature reveals that as gas pressure increases, the temperature also increases.

4. This relationship using the concepts of molecular velocity and collisions of molecules reveals that as the temperature increases, the velocity and number of collisions causing increases, causing a rise in pressure.

5. An equation to express the relationship between pressure and temperature (K) is K=P/T.

5. The values of the data were kept at a very constant rate.

6. According to this experiment, if the Kelvin temperature of a gas is doubled, the pressure of the gas also should nearly double.

## The FInal Conclusion

Throughout this essay, I was able to understand that as the temperature increased, the pressure increased. Therefore, as they both increased, it looked like they were going to plateau.