Advertisements
Advertisements
Question
Explain the change in internal energy of a thermodynamic system (the gas) by heating it.
Advertisements
Solution
Consider a gas filled in a cylinder fitted with a massless, movable, and frictionless piston as shown in the figure.
Let Ts be the temperature of gas (system),
TE be temperature of environment.
Initially, the cylinder is heated using a burner, as illustrated in the picture. At this level, TE exceeds Ts. The temperature difference between the source of heat and the system causes energy to flow towards the gas in the cylinder. This increases the gas's internal energy. When the environment is cooler than the gas, Ts > TE, resulting in energy transfer from the gas to the surroundings.
The gas expands as a result of the piston being forced out during this procedure. The gas does a certain amount of work. The gas cools, and some of its energy is lost. This describes how exerting effort can alter a gas's intrinsic energy.
APPEARS IN
RELATED QUESTIONS
Explain why Two bodies at different temperatures T1 and T2, if brought in thermal contact, do not necessarily settle to the mean temperature (T1 + T2)/2.
A steam engine delivers 5.4×108 J of work per minute and services 3.6 × 109 J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?
The outer surface of a cylinder containing a gas is rubbed vigorously by a polishing machine. The cylinder and its gas become warm. Is the energy transferred to the gas heat or work?
A closed bottle contains some liquid. the bottle is shaken vigorously for 5 minutes. It is found that the temperature of the liquid is increased. Is heat transferred to the liquid? Is work done on the liquid? Neglect expansion on heating.
The final volume of a system is equal to the initial volume in a certain process. Is the work done by the system necessarily zero? Is it necessarily nonzero?
Can work be done by a system without changing its volume?
Consider the following two statements.
(A) If heat is added to a system, its temperature must increase.
(B) If positive work is done by a system in a thermodynamic process, its volume must increase.
Consider two processes on a system as shown in figure.
The volumes in the initial states are the same in the two processes and the volumes in the final states are also the same. Let ∆W1 and ∆W2 be the work done by the system in the processes A and B respectively.
A gas is contained in a metallic cylinder fitted with a piston. The piston is suddenly moved in to compress the gas and is maintained at this position. As time passes the pressure of the gas in the cylinder ______________ .
The pressure p and volume V of an ideal gas both increase in a process.
(a) Such a process is not possible.
(b) The work done by the system is positive.
(c) The temperature of the system must increase.
(d) Heat supplied to the gas is equal to the change in internal energy.
Figure shows three paths through which a gas can be taken from the state A to the state B. Calculate the work done by the gas in each of the three paths.
A gas is taken along the path AB as shown in figure. If 70 cal of heat is extracted from the gas in the process, calculate the change in the internal energy of the system.
Figure shows a cylindrical tube of volume V with adiabatic walls containing an ideal gas. The internal energy of this ideal gas is given by 1.5 nRT. The tube is divided into two equal parts by a fixed diathermic wall. Initially, the pressure and the temperature are p1, T1 on the left and p2, T2 on the right. The system is left for sufficient time so that the temperature becomes equal on the two sides. (a) How much work has been done by the gas on the left part? (b) Find the final pressures on the two sides. (c) Find the final equilibrium temperature. (d) How much heat has flown from the gas on the right to the gas on the left?
A mixture of fuel and oxygen is burned in a constant-volume chamber surrounded by a water bath. It was noticed that the temperature of water is increased during the process. Treating the mixture of fuel and oxygen as the system,
- Has heat been transferred?
- Has work been done?
- What is the sign of ∆U?
A system releases 130 kJ of heat while 109 kJ of work is done on the system. Calculate the change in internal energy.
Which of the following is correct, when the energy is transferred to a system from its environment?
One gram of water (1 cm3) becomes 1671 cm3 of steam at a pressure of 1 atm. The latent heat of vaporization at this pressure is 2256 J/g. Calculate the external work and the increase in internal energy.
An ideal gas is compressed at a constant temperature. Its internal energy will ____________.
Two samples A and B, of a gas at the same initial temperature and pressure are compressed from volume V to V/2; A isothermally and B adiabatically. The final pressure of A will be ______.
Which of the following represents isothermal process?
Two cylinders A and B of equal capacity are connected to each other via a stopcock. A contains a gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stopcock is suddenly opened. Answer the following:
What is the change in the temperature of the gas?
In thermodynamics, heat and work are ______.
An expansion process on a diatomic ideal gas (Cv = 5/2 R), has a linear path between the initial and final coordinates on a pV diagram. The coordinates of the initial state are: the pressure is 300 kPa, the volume is 0.08 m3 and the temperature is 390 K. The final pressure is 90 kPa and the final temperature s 320 K. The change in the internal energy of the gas, in SI units, is closest to:
The internal energy of one mole of argon at 300 K is ______. (R = 8.314 J/mol.K)
What is heat?
A system releases 125 kJ of heat while 104 kJ work is done on the system. Calculate the change in internal energy.
