Name: ___________________ Date: __________

EXPERIMENT

GAS PRESSURE LAW (GAY-LUSSAC’S LAW)

1.0 OBJECTIVE:

To study the relationship between pressure p and temperature T of fixed mass of air at constant volume V.

2.0 INTRODUCTION

At temperatures higher than the room temperature, air is closely behaving like an ideal gas. Therefore, the use of air as the sample in this experiment for the study of the behaviour is adequate.

A fixed amount of air was trapped by mercury inside a closed end tube. The pressure p, the volume V and the temperature T of the gas are the variable parameters. The pressure, volume and temperature of the gas at a certain situation is called a state. These variables are related in an equation called the equation of state. When a variable is changed, then the other variables will also change to make the gas a different state.

Gas pressure law describes the variation of V with T when p is kept constant. This is also called the Gay-Lusaac’s law.

In the equation of state for an ideal gas, the parameters p, V and T are related by the equation:

p = PressureV = VolumeT = Temperaturek = Boltzmann’s Constant

3.0 APPARATUS

1. Computer2. PHOENIX Data Logger3. Pressure sensor (20 to 250kPa)4. Temperature sensor (-40 to +400oC) 5. Transparent PVC tube6. Heater7. 600 ml Beaker8. Retort stand9. 100 ml Erlenmeyer Flasks

4.0 EXPERIMENTAL SET UP

Figure 1 Circuit Connection of Pressure and PT100 Temperature Sensors

Figure 2 Circuit Diagram of Pressure and PT100 Temperature Sensors

470Ω

PHOENIX Data Logger

Phidgets Pressure Sensor

Stopper

Rubber Tube

PT100 Temperature Sensor

USB

CH

1

GND

ADC 0-5V

4GND Rg IN

OUT

Black

PT100Red

5V

1mA CCS

CH

0

GND

White

Red PressureSensor

Black

PHOENIX Data Logger

*CCS – constant current source, GND – ground, Rg - 470Ω resistor, CH – channel, ADC – Analog Digital Converter

Figure 3 User Interface of MBL Courseware

Figure 4 Gas Pressure Law Experiment Setup

Data DisplayRename the save file

Slider for change the range Instruction Message

Heater

Temperature Sensor

Pressure Sensor

Retort Stand

Erlenmeyer Flasks

Stopper

Data Logger

5.0 PROCEDURE

a) Computer Setup:1. Ensure that the Data Logger is connected to the computer.2. Open the MBL Courseware file that included for this experiment.3. Pressure sensor uses a 3-pin connector; + 5.0 volt DC, ground, and an analog

input (ADC) with a range of 0.0 to 5.0 volt. Plug the Pressure Sensor into PHOENIX data logger (see Figure 2).

4. Connect the PT100 temperature sensor to 1mA constant current source and non-inverting variable gain amplifier (GND-IN-OUT) using 470Ω (see Figure 2).

5. When the MBL Courseware file is opened, you should see two graphs (Pressure vs. Time and temperature vs. Time) refer to Figure 3.

6. Arrange the display by slide the Time Scale to 1200 second (20 minutes).

7. Click the Start button ( ) and Stop button ( ) to test the courseware.

8. Click the Help button ( ) to guide you on how to use the courseware.9. You can proceed to the experimental setup.

b) Experimental setup (see Figure 4):1. Plug the stopper on the Erlenmeyer Flasks.2. Immerse the Erlenmeyer Flasks into water.3. Heat up the water.

4. Click the Start button ( ) to begin collecting data and plotting the graph.

5. When the temperature get into approximately 75oC (refer to the Data Display

in Figure 3), click the Stop button ( ) to end data collection and remember to switch off the heater.

6. Rename the data file (pre_temp.dat).

7. Click the Save button ( ) to save the data into the containing folder (MBL folder).

8. Open the data file (pre_temp.dat) using OpenOffice.com Calc (Spreadsheet).9. Fill in the pressure data into the table provided.

6.0 DATA

Table 1 Temperature and Pressure

Temperature, T (oC) Pressure, p (kPa)

35

40

45

50

55

60

65

70

75

7.0 ASSIGNMENT

1. From the table, plot graph of p against T (in oC).2. What is the relationship between the pressure and temperature for gas pressure

law experiment?3. Determine the gradient and intercept from the Graph Pressure versus

Temperature.4. What is the temperature when p = 0? Explain your answer.

Teacher’s Note – Pressure Law Experiment:

a) Data Analysis using Open Office:

1. Once the pressure data collected, teacher can fill those data into the Pressure Law Analysis (Open Office scalc file).

2. Then, the graph and equation will show automatically. Fill in the parameters from equation into the box provided.

Step 1

Step 2

3. The absolute temperature and percentage error will show automatically. After that, fill in the absolute temperature in the box (B11).

4. Once the 3 steps completed, the result will show as below.

Step 3

b) Data Analysis using Microsoft Excel:

1. Once the pressure data collected, teacher can fill those data into the Pressure Law Analysis (Microsoft Excel file).

2. Then, the graph and equation will show automatically. Fill in the parameters from equation into the box provided.

Step 1

Step 2

3. Once the 2 steps completed, the result will show as below.