First law of thermodynamics and internal energy - Question Bank

1. For an ideal gas, the change in internal energy depends solely on the change in:
A) Volume
B) Pressure
C) Temperature
D) Enthalpy
2. If a system undergoes a process where ΔU = 100 J and Q = 50 J, what is the work done by the system?
A) 50 J
B) -50 J
C) 150 J
D) -150 J
3. The First Law of Thermodynamics is applicable to:
A) Chemical reactions only
B) Physical processes only
C) All natural phenomena involving energy
D) Ideal gases only
4. Consider a system where 50 J of work is done ON the system, and 100 J of heat is supplied. What is the change in internal energy?
A) 50 J
B) 150 J
C) -50 J
D) -150 J
5. Which of the following quantities is NOT a measure of energy?
A) Internal Energy
B) Heat
C) Work
D) Pressure
6. In the equation ΔU = Q - W, if the process is such that W = Q, then:
A) ΔU > 0
B) ΔU < 0
C) ΔU = 0
D) ΔU is indeterminate
7. The internal energy of a substance is dependent on:
A) Pressure and Volume
B) Temperature and Phase
C) Heat supplied and Work done
D) Only Temperature
8. If a system releases 200 J of heat and its internal energy decreases by 100 J, how much work is done ON the system?
A) 100 J
B) 200 J
C) 300 J
D) -100 J
9. When a system expands against a constant external pressure, the work done BY the system is given by:
A) -PΔV
B) PΔV
C) ΔU
D) Q
10. For a polyatomic ideal gas, the internal energy per mole is U = (f/2)RT, where 'f' is the number of degrees of freedom. If f=6, what is the change in internal energy when 2 moles are heated by 50 K?
A) 150 R
B) 300 R
C) 600 R
D) 1200 R
11. What is the change in internal energy when 100 J of heat is supplied to a system, and 100 J of work is done by the system?
A) 100 J
B) -100 J
C) 200 J
D) 0 J
12. If a gas is heated at constant volume, what is the work done by the gas?
A) Positive
B) Negative
C) Zero
D) Cannot be determined
13. Which statement is FALSE regarding the First Law of Thermodynamics?
A) It relates heat, work, and internal energy.
B) It is a statement of energy conservation.
C) It dictates the direction of heat flow.
D) It applies to all thermodynamic processes.
14. In an isobaric process, heat is added to a system, and the system expands. What happens to the internal energy?
A) It increases.
B) It decreases.
C) It remains constant.
D) It is equal to the work done.
15. If a system does 50 J of work and absorbs 30 J of heat, what is the change in internal energy?
A) 80 J
B) -20 J
C) 20 J
D) -80 J
16. What does the term 'internal energy' in thermodynamics encompass?
A) Only the kinetic energy of molecules.
B) Only the potential energy between molecules.
C) The sum of kinetic and potential energies of molecules within the system.
D) The total energy of the system including translational, rotational, and vibrational energies.
17. For a system at constant temperature undergoing a process, the change in internal energy is:
A) Always positive
B) Always negative
C) Zero for an ideal gas
D) Dependent on pressure
18. If a system's internal energy increases by 200 J and it does 100 J of work, how much heat was supplied?
A) 100 J
B) 200 J
C) 300 J
D) 0 J
19. Which statement is true about work done in thermodynamic processes?
A) Work is a state function.
B) Work is always positive for expansion.
C) Work is path-dependent.
D) Work is equal to heat in all processes.
20. The internal energy of a system is 500 J. If 300 J of heat is added and 100 J of work is done by the system, what is the final internal energy?
A) 700 J
B) 800 J
C) 900 J
D) 300 J
21. What is the value of Q when ΔU = -100 J and W = 30 J (work done by the system)?
A) -70 J
B) 70 J
C) -130 J
D) 130 J
22. If a system is compressed adiabatically, what happens to its internal energy?
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero
23. For an ideal gas, internal energy is a function of:
A) Pressure and Volume
B) Temperature only
C) Volume and Temperature
D) Pressure and Temperature
24. In a system where 200 J of heat is removed and 50 J of work is done on the system, what is the change in internal energy?
A) -150 J
B) -250 J
C) 150 J
D) 250 J
25. The First Law of Thermodynamics prohibits:
A) Perpetual motion machines of the first kind (machines that produce work without consuming energy).
B) Heat transfer from hot to cold bodies.
C) Conversion of work into heat.
D) Changes in internal energy.
26. For a diatomic ideal gas, the internal energy per mole is U = (5/2)RT. If 1 mole of this gas undergoes an isobaric expansion where heat added is 250 J, what is the change in internal energy?
A) 150 J
B) 250 J
C) 200 J
D) 100 J
27. Which of the following is NOT a form of energy transfer that affects internal energy?
A) Heat
B) Work
C) Mass transfer
D) Radiation
28. What is the value of Q for a system that performs 100 J of work and experiences a decrease in internal energy of 50 J?
A) 50 J
B) 150 J
C) -50 J
D) -150 J
29. When a gas expands, it does work on the surroundings. If this expansion occurs adiabatically, what happens to the internal energy of the gas?
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero
30. If Q = 50 J and W = 20 J (work done by the system), what is ΔU?
A) 70 J
B) 30 J
C) 50 J
D) 20 J
31. The internal energy of a real gas differs from that of an ideal gas primarily because:
A) Real gases have intermolecular forces.
B) Real gases have negligible molecular volume.
C) Real gas molecules possess kinetic energy only.
D) Real gases obey the ideal gas law perfectly.
32. Which type of process involves no change in internal energy for an ideal gas?
A) Isobaric
B) Isochoric
C) Isothermal
D) Adiabatic
33. If work is done ON the system (W is negative in the formula ΔU = Q - W), and heat is released by the system (Q is negative), what happens to the internal energy?
A) Increases
B) Decreases
C) Remains constant
D) Cannot be determined
34. In a cyclic process, the system returns to its initial state. What is the change in internal energy for a cyclic process?
A) Always positive
B) Always negative
C) Always zero
D) Depends on the path
35. What is the internal energy of an ideal gas at absolute zero temperature (0 K)?
A) Infinite
B) Zero
C) Minimum possible value
D) Cannot be determined
36. If a system does work on the surroundings (W > 0) and absorbs heat (Q > 0), its internal energy will:
A) Increase
B) Decrease
C) Remain unchanged
D) Cannot be determined without more information
37. For a process where ΔU = 0, what is the relationship between heat and work?
A) Q = W
B) Q = -W
C) Q = 0
D) W = 0
38. Which of the following is a state function in thermodynamics?
A) Heat (Q)
B) Work (W)
C) Internal Energy (U)
D) Enthalpy Change (ΔH)
39. In adiabatic processes, there is no heat exchange with the surroundings. What is the consequence for the internal energy according to the First Law?
A) Internal energy remains constant.
B) Internal energy changes solely due to work done.
C) Internal energy is always zero.
D) Internal energy change is equal to heat supplied.
40. The First Law of Thermodynamics is essentially a statement of the conservation of:
A) Mass
B) Momentum
C) Energy
D) Charge
41. If heat is supplied to a system and its internal energy decreases, what must have happened to the work done?
A) It must be zero.
B) It must be positive (work done by the system).
C) It must be negative (work done on the system).
D) It is indeterminate.
42. What is the work done by a system during an isochoric process (constant volume)?
A) Positive
B) Negative
C) Zero
D) Depends on heat exchange
43. For a monatomic ideal gas, the internal energy per mole is given by U = (3/2)RT. What is the change in internal energy when 2 moles of this gas are heated from 300 K to 400 K?
A) 1500 R
B) 750 R
C) 3000 R
D) 100 R
44. In an isothermal process for an ideal gas, the temperature remains constant. What can be said about the change in internal energy?
A) It increases.
B) It decreases.
C) It remains constant.
D) It is equal to the heat exchanged.
45. What is the nature of internal energy for an ideal gas?
A) It depends only on pressure.
B) It depends only on volume.
C) It depends only on temperature.
D) It depends on pressure, volume, and temperature.
46. Consider an isolated system. According to the First Law of Thermodynamics, what is the change in internal energy if no heat is exchanged with the surroundings?
A) Equal to the work done
B) Zero
C) Equal to the heat supplied
D) Dependent on temperature
47. If a system absorbs 100 J of heat and performs 40 J of work, what is the change in its internal energy?
A) 60 J
B) 140 J
C) 40 J
D) 100 J
48. What does 'ΔU' symbolize in the equation ΔU = Q - W, where ΔU is the change in internal energy, Q is heat added, and W is work done by the system?
A) Heat transferred
B) Work done on the system
C) Change in internal energy
D) Enthalpy change
49. In the context of the First Law of Thermodynamics, what does the term 'Q' represent?
A) Work done by the system
B) Change in internal energy
C) Heat supplied to the system
D) Enthalpy of the system
50. Which of the following statements best describes the First Law of Thermodynamics?
A) Energy cannot be created or destroyed, only converted from one form to another.
B) The entropy of an isolated system never decreases over time.
C) Heat spontaneously flows from a colder body to a hotter body.
D) The pressure and volume of a gas are inversely proportional at constant temperature.
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