ABSTRACT/SUMMARY

The aim of this experiment is to determine the properties of measurement/PVT. The equipment that had been used is called Perfect Gas Expansion and by using this kind of equipment, all 7 experiments were conducted successfully. For the first experiment, we conducted to show the Boyles Law. In this experiment, the experiment is done for three times from pressurized chamber to vacuum chamber, from atmospheric chamber to pressurized chamber and pressurized chamber to vacuum chamber. Next, the second experiment is to determine the Gay-Lussac Law and it also done repeatedly for three times to get the average value of the temperature at pressurize and depressurize vessels. After getting the average value, the graph of pressure versus temperature is plotted. The third experiment is to demonstrate the isentropic expansion process. In this experiment, the pressure and the temperature of pressurized chamber is taken before and after the expansion occur. The forth, fifth and sixth experiment are stepwise depressurization, bried depressurization and determine of ratio volume, The last experiment we need to determine the ratio of heat capacity. Only the pressurized chamber and compressive pump are used during this experiment. Based on all the experiments that was conducted, all the data which are about the reading before and after the setting are recorded into the data as below. The experiment was successful. INTRODUCTION

The Perfect Gas Expansion Apparatus is a self-sufficient bench top unit designed to enable students to familiarize with some fundamental thermodynamic processes. Comprehensive understanding of First Law of Thermodynamics, Second Law of Thermodynamics and the P-V-T relationship is fundamentally important in the applications of thermodynamics in the industry. The apparatus comes with one pressure vessel and one vacuum vessel and both are made of glass tubes. The vessels are linked to one another with a set of piping and valves. A large diameter pipe provides gradual or instant change. Air pump is included to enable us to pressurize or evacuate air inside the large vessels provided the valves configures appropriately during the experiment. The pressure and temperature sensors are used to monitor and manipulate the pressure and temperature inside the vessels and the digital indicator will display the pressure and temperature on the control panel. This experiment dealt a lot with the properties of an ideal gas and its relationship with the various environmental factors. An ideal gas is said to be a gas which obeys the P-V-T relationship. A PVT relationship is one of the forms of the equations of state, which relates the pressure, molar volume V and the temperature T of physically homogeneous media in thermodynamic equilibrium.

Other than that, ideal gas is also a gas that exhibits simple linear relationships among volume, pressure, temperature and amount . Gas particles in a box collide with its walls and transfer momentum to them during each collision. The gas pressure is equal to the momentum delivered to a unit area of a wall, during a unit time. However, ideal gas particles do not collide with each other but only with the walls. A single particle moves arbitrarily along some direction until it strikes a wall. It then bounces back, changes direction and speed and moves towards another wall. The gas expansion equations are derived directly from the law of conservation of linear momentum and the law of conservation of energy .

OBJECTIVES

Experiment 1: Boyles Law ExperimentTo determine the relationship between pressure and volume of an ideal gas.To compare the experimental results with theoretical results.Experiment 2: Gay-Lussac Law ExperimentTo determine the relationship between pressure and temperature of an ideal gas.Experiment 3: Isentropic Expansion processTo demonstrate the isentropic expansion process.Experiment 4: Stepwise DepressurizationTo study the response of the pressurized vessel following stepwise depressurization.Experiment 5: Brief DepressurizationTo study the response of the pressurized vessel following a brief depressurization.Experiment 6: Determination of ratio of volumeTo determine the ratio of volume and compares it to the theoretical value.Experiment 7: Determination of ratio of heat capacityTo determine the ratio of heat capacity.

THEORY

Boyles Law ExperimentBoyle's Law states that the product of the pressure and volume for a gas is a constant for a fixed amount of gas at a fixed temperature. Written in mathematical terms, this law isP x V = constantA common use for this law is to predict on how a change in pressure will alter the volume of gas or vice versa. Therefore, for initial values of p1and V1, which change to final values of p2and V2, the following equation appliesP1x V1= P2x V2(for fixed amount of gas at constant temperature)The graph shows how the pressure and volume vary according to Boyles Law at two difference temperatures. Then it can be conclude that, the pressure and volume gas is indirectly related which is if the pressure of the chamber is increase then the volume of the gas inside the chamber also decrease. Besides, it also involves the kinetic energy. If we decrease the volume of a gas, thus means that the same number of gas particles are now going to come in contact with each other and with the sides of the container much more often. The pressure is also measure the frequency of collision of gas particle with each other and with the side of the container they are in. Thus if the volume decrease, the pressure will naturally increase. The opposite is true if the volume of the gas is increased, the gas particles collide less frequently and the pressure will decrease. . At lower temperatures the volume and pressure values are lower. Any volume or pressure units can be used as long asboth P'sandboth V'shave thesame units. The particle theory and simple arithmetical values is used toexplain Boyles Law. When the volume of gas is compress into half, the collision of the gas will increase and thus the pressure will increase double compare to the origin value. But if the volume of the gas is doubled or increase in the factor of two, the collision drop and decrease thus the pressure will decrease into half compare to the origin.

Gay-Lussac Law theoryCompare to the Boyles Law, the expression of Gay-Lussacs Law is used for each of the two relationship named after the French chemist Joseph Louis Gay-Lussac (1778-1850) and which concern the properties of gases, though it is more usually applied to his law of combining volumes. One law relates to volumes before and after chemical reaction while the other concerns the pressure and temperature relationship for a sample of gas. According toGay-Lussacs law,for a given amount of gas held at constant volume, the pressure is proportional to the absolute temperature.Mathematically,

Where, kGis the appropriate proportionality constant.Besides, Gay-Lussac law also tells us that it may be dangerous to heat a gas in a closed container. The increased pressure might cause the container to explode. Therefore, for initial values of p1and T1, which change to final values of p2and T2, the following equation applies

In all calculations, the absolute or Kelvin scale of temperature must be used forT(K =oC + 273).

The graph shows how the pressure and temperature vary according to Gay-Lussac Law. Based on Gay-Lussac it stated that the pressure exerted on a containers sides by an ideal is proportional to the absolute temperature of the gas. This follows from the kinetic theory which stated that by increasing the temperature of the gas, the molecules speed increase meaning an increased amount of collisions with the container walls.

Isentropic Expansion Process Isentropic basically means no change in entropy. According to grc.nasa.gov, entropy has a variety of physical interpretations, including the statistical disorder of the system, but often perceived to be just another property of the system, like enthalpy or temperature. The Second Law of thermodynamics can be expressed in terms of the entropy, S, as another state of function: The entropy of an isolated system increases in the course of a spontaneous change:Stot > 0Where Stot is the total energy of the system and its surroundings. Thermodynamically irreversible processes (like cooling to the temperature of surroundings and the free expansion of gases) are spontaneous processes, and hence must be accompanied by an increase in total entropy (Atkins, 2002: 92).However, for a reversible and an adiabatic process, the value of entropy, S, remains the same from the initial to the state of completion. S = 0S1 = S2

Stepwise Depressurization ExperimentThe stepwise depressurization is conducted by depressurizing the pressurized chamber or tank gradually by releasing the gas expansion at every instance the valves are opened and closed to see the gradual changes in pressure within the container. Pressure decreases with the expansion.

Brief Depressurization ExperimentSimilar procedures as previous lab practical, but the time interval of valves opening increased to a few seconds. This is so that the effects or response of brief depressurization of the gas could be observed. With the increased time interval, the gas should expand faster.

Determination of Ratio of Volume ExperimentThe ratio of volume of gas expansion between the chambers and the atmosphere should be the same (or at least almost) with the theoretical value. The following equations can be used to evaluate and calculate the values:P1 V1 = P2 V2V2/ V1 = P1/ P2V2/ V1 = Ratio valueDetermination of ratio of heat capacity theoryFor a perfect gas,Cp = Cv + RWhere, Cp = molar heat capacity at constant pressure, andCv = molar heat capacity at constant volume.For a real gas a relationship may be defined between the heat capacity, which is dependent on the equation of state, although it is more complex than that for a perfect gas. The heat capacity ratio may then be determined experimentally using a two step process.1. An adiabatic reversible expansion from the initial pressure Ps to an intermediate pressure Pi{Ps, Vs, Ts} {Pi, Vi, Ti}2. A return of the temperature to its original value Ts at constant volume Vi{Pi, Vi, Ti} {Pf, Vi, Ts}For a reversible adiabatic expressiondq = 0From the First Law of Thermodynamics,dU = dq + dWTherefore during the expansion processdU = dWordU = -pdV

At constant volume the heat capacity relates the change in temperature to the change in internal energydU = CvdTSubstituting in to equation x,CvdT = -pdVSubstituting in the ideal gas law and then integrating gives

Now, for an ideal gas

Therefore,

Rearranging and substituting in from equation x,

During the return of the temperature to the starting value,

Thus,

Rearranging gives the relationship in its required form:

APPARATUS

There was only one equipment used for all the experiments, and that is the Solteq Perfect Gas Expansion Apparatus (Model: TH11).

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Figure 3: Solteq Perfect Gas Expansion Apparatus (Model: TH11).Including:1. Pressure Transmitter 2. Pressure Relief Valve 3. Temperature Sensor 4. Atmospheric Chamber 5. Vacuum Glass6. Vacuum Pump

METHOD/ PROCEDURES

General Operation:Start-up: 1. The equipment was connected to single phase power supply and then the switch was turned on.2. All the valves were fully opened and the pressure reading was checked on the panel. This is to make sure that the chambers were all under atmospheric pressure. 3. The valves were all closed again afterwards. 4. The pipe from compressive port of the pump was connected to pressurized chamber.5. The unit was ready for use.

General Operation:Shut-down:1. The pump was switch off and both pipes were removed from the chambers2. The valves were fully open to release the air inside the chambers3. The power supply and main power were switch off

Experiment 1:1. The general start up method as previously mentioned was performed and the valves were once again made sure to be fully closed.2. The compressive pump was switched on and the pressure inside the chamber was allowed to increase up to about 150kPa. Then, the pump was switched off and the hose was removed from the chamber.3. The pressure reading inside the chamber was monitored until it stabilized.4. The pressure reading for both chambers before expansion was recorded. 5. The V 02 was fully opened and the pressurized air flows were allowed into the atmospheric chamber. 6. The pressure reading for both chambers after expansion was recorded.7. The experimental methodology was repeated for the following conditions: From atmospheric chamber to vacuum chamber; From pressurized chamber to vacuum chamber. 8. The PV value was calculated and Boyles Law was proven in further sections

Experiment 2:1. The general start up method was performed again. 2. The hose was connected from the compressive pump to pressurized chamber. 3. The compressive pump was switched on and the temperature for every increment of 10kPa in the chamber was recorded. The pump was stopped when the pressure PT 1 reaches about 160kPa. 4. Then, the valve V 01 was slightly opened and the pressurized air was allowed to flow out. The temperature reading for every decrement of 10kPa was recorded.5. The experiment was stopped when the pressure reached atmospheric pressure.6. The experiment was repeated for three times to get the averag7. 7.A graph was plotted to represent the pressure versus temperature

Experiment 3:1. The general start up procedures was performed. 2. The hose was connected from compressive pump to pressurized chamber.3. The compressive pump was switched on and the pressure inside the chamber was allowed to increase until about 160kPa. Then, the pump was switched off and the hose was removed from the chamber. 4. The pressure reading inside the chamber was monitored until it stabilized. The pressure reading PT 1 and temperature TT 1 were recorded. 5. Valve V 01 was slightly opened and air was allowed to flow out slowly until it reached atmospheric pressure.6. The pressure reading and the temperature reading after the expansion process were recorded. 7. The isentropic expansion process was discussed in further section

Experiment 4:1. The general start up procedure was performed. 2. The hose from the compressive pump was connected to the pressurized chamber.3. The compressive pump was switched on and the pressure inside the chamber was allowed to increase until about 160kPa. The pump was then switched off and the hose was removed from its chamber. 4. The pressure reading inside the chamber was monitored until it stabilized. The pressure reading PT 1 was recorded. 5. The valve V 01 was fully opened and brought back to closed position instantly. The pressure reading PT 1 was monitored and recorded until it became stable. 6. Step 5 was repeated at least four times7. The pressure reading was display on the graph and was discussed about it.

Experiment 5:1. General start up procedure was performed. 2. The hose was connected from the compressive pump to the pressurized chamber.3. The compressive pump was switched on and allowed to increase the pressure inside the chamber until about 160kPa. Then it was switched off and the hose was removed. 4. The pressure reading inside the chamber was monitored until it stabilized. The pressure reading was recorded as PT 1. 5. The valve V 01 was fully opened and brought back to closed position after a few seconds. The pressure reading after expansion was monitored and recorded as PT 1 until it became stable.6. The result was displayed on graph and further discussed.

Experiment 6:1. General start up procedure was performed and valves were made sure to be closed.2. Compressive pump was switched on and the pressure inside the chamber was allowed to increase up to about 150kPa. Then, the pump was switched off and the hose was removed from the chamber.3. The pressure reading inside the chamber was monitored until it stabilized. 4. The pressure reading for both chambers was recorded before expansion.5. Valve V 02 was opened and the pressurized air was allowed to flow into the atmospheric chamber slowly.6. The pressure reading for both chambers after expansion was recorded.7. The experimental procedures were repeated for the following conditions: From atmospheric chamber to vacuum chamber. From pressurized chamber to vacuum chamber.8. The ratio of volume was calculated and compared with the theoretical value

Experiment 7:1. The general start up method was performed. 2. The compressive pump was connected to pressurized chamber. 3. The compressive pump was switched on and the pressure inside the chamber was allowed to increase until about 160kPa. Then, the pump was switched off and the hose was removed from the chamber.4. The pressure reading inside the chamber was monitored until is stabilized. The pressure reading PT1 and temperature TT1were recorded.5. The valve V 01 was fully opened and brought back to closed until after a few seconds. The reading PT1 and temperature TT1 were monitored and recorded until they became stable.6. The ratio of the heat capacity was determined and then compared with the theoretical value