Investigation of Relationship Between Pressure, Volume and Temperature of Gas

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F.6 Physics Laboratory Report
Investigation of relationship
between pressure, volume and temperature of gas

Date of experiment: 12/11/2008

Aim of experiment:
The objective of this experiment is:
1. To study the relationship between pressure and volume of a gas at constant temperature. 2. To study the relationship between the volume and temperature of a gas at constant pressure.

Principles involved:
When gases are compared, their volumes, temperatures and pressure are always involved. The volume of a gas is identical to the volume of the container holding it. The temperature of the gas is related to the average kinetic energy of its molecules. The gas pressure originates from the bombardments of the molecules with the container wall.

By combining Boyle’s Law, Charles’ Law and Avogadro’s Law, the General Gas Law (or ideal gas law) is proposed. It reveals the relationship between the three properties of a gas, which is pressure, volume and temperature, in a container. It states: pV = nRT

where p is the pressure,
V is the volume,
T is the temperature of the gas at Kelvin scale,
R is the molar gas constant, and
n is the number of moles.

Apparatus:
Boyle’s Law apparatusx 1
Bourdon gaugex 1
Pumpx 1
Beaker (2L)x 1
Capillary tube with coloured dye threadx 1
Bunsen burnerx 1
Thermometerx 1
Rubber tubingx 1
Clipx 1
Half-metre ruler x 1
Stirrer x 1
Tripod with wire gauze x 1
Retort stands and clampx 1
Ice cubes

Procedure:
Part A: Relationship between pressure and volume
1. The Boyle’s Law apparatus was set up as shown below.

2. The tap was opened initially and the pump was pressed gently to increase the pressure of the gas column and then the tap was closed immediately. 3. The volume of the trapped gas column and the reading of the Bourdon gauge were recorded. 4. By releasing the tap gradually or pressing the pump harder, the reading of the Bourdon gauge was differed. 5. Steps 3 and 4 were repeated several times to obtain the different volumes and pressures of the trapped air column. 6. The results were tabulated and the graphs of pressure (p) of the gas against its volume (V) at room temperature and p against 1/V were plotted.

Part B: Relationship between volume and temperature
1. The apparatuses were set up as shown below. The end of the air column was tighten by clipping tightly a rubber tube which was connected to the capillary tube. 2. A capillary tube with coloured dye thread and a thermometer were immersed into a mixture of ice and water. 3. The length of the air column in the capillary tube (l) and the reading of the thermometer (T) were recorded when the values became steady. 4. The water bath was then heated by Bunsen burner and stirring was kept on. When the temperature rose about 10oC, the Bunsen burner was removed. T and l were recorded when they were steady. 5. Step 3 was repeated several times to obtain l at different T and the results were tabulated. 6. A graph of length (l) of the air column, which is proportional to volume (V), against its temperature (T) at constant pressure was plotted.

Precaution:
1. The junctions of the apparatuses in Part A of the experiment were held and pressed tightly. It was to ensure the set-up was air-tight so that the pressure of the gas column would not decrease gradually even when the tap was closed. 2. After pressing the pump, the tap was closed immediately. It was to ensure the pressure of the gas column could be increased and maintained. 3. All readings and measurements were recorded only when they became steady to ensure accurate results. 4. Throughout Part B of the experiment, the air column below the coloured dye thread was always immersed in water completely to ensure accurate results. 5. Stirring was always kept on throughout Part B of the experiment as this could ensure the temperature of the water bath was evenly spread. This could enable...
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