Target: 10 Questions in 10 minutes

An IB Physics data booklet is helpful
 1+2. The first law of thermodynamics is given as Q = ΔU + W.

1. In a real gas, ΔU is the change in..

  • A. the total kinetic energy of particles
  • B. the total potential energy of particles
  • C. the total of kinetic and potential energy of the particles
  • D. the heat transferred to the particles

2. Which of the following correctly gives the direction of energy transfer for positive values of Q and W?

 Q W
A
 heat transferred to system work done on system
B
 heat transferred to system work done by system
C
 heat transferred from system work done on system
D
 heat transferred from system work done by system


3-5. The gas in a large syringe expands as it is heated. The pressure remains constant at 105 pascals, and 2 J of work is done as it expands.

syringe

  

3. What is the increase of volume during this expansion?

  • A. 0.2 cm3
  • B. 2 cm3
  • C. 20 cm3
  • D. 200 cm3

4. if 6 J of heat was supplied to the syringe, what is the change in internal energy of the gas?

  • A. +6 J
  • B. - 6 J
  • C. +4 J
  • D. -4 J

5. The experiment is repeated with n moles of gas, and this time the syringe has an internal energy change of +5 J. Which of the following gives the change in temperature of the gas?

  • A. ${{15 \, n \, R} \over {2}}$
  • B. ${{10 \ n \ R} \over {3}}$
  • C. ${{10} \over {3 \, n \, R}}$
  • D. ${{15 } \over { 2 \, n \, R}}$
6. An aerosol can contains many gas particles under pressure. When the gas is released the pressure decreases. Which of the following options best describes the change in entropy and disorder of particles as the gas is released? aerosol can
entropy disorder
A
 increases decreases
B
 increases increases
C
 decreases decreases
D
 decreases increases

7. A bike pump can be used to push air into a tyre. Which of the following best describes the changes in entropy as this happens?

  • A. Entropy of air pumped in to the tyre decreases, but the entropy of the pump and surroundings has an equal or larger entropy increase
  • B. Entropy of air pumped in to the tyre increases, but the entropy of the pump and surroundings has an equal or larger entropy decrease
  • C. Entropy of air pumped in to the tyre decreases, but the entropy of the pump and surroundings has an equal or smaller entropy increase
  • D. Entropy of air pumped in to the tyre increases, but the entropy of the pump and surroundings has an equal or smaller entropy decrease

8. Cubes of a frozen liquid of mass m and at a temperature of T °C are melting. The latent heat of fusion of ice is L.

ice cubes melting

 

  

8. What is the change of entropy of the cubes when they have melted?

  • A. increase of ${{mL} \over {T}}$
  • B. decrease of ${{mL} \over {T}}$
  • C. increase of ${{mL} \over {T + 273}}$
  • D. decrease of ${{mL} \over {T + 273}}$

9+10. Two moving particles are trapped within the left side of a box by a partition. The partition is lifted allowing the particles to move freely throughout the box.

2 particles trapped in left side of box - thermodynamics

The partition is randomly replaced, trapping one particle on each side of the box.

if:

  • P = total number of final possible microstates of particles in the box
  • Q = number of microstates in which one particle is in each side of the box

9. What are the values of P and Q?
P Q
A
 3 1
B
 3 2
C
 4 1
D
 4 2

10. What is the change of entropy in moving from the initial state of two particles in the left side to the final state of one particle being in each side of the box?

  • A. kB( ln(Q) - ln(1) )
  • B. kB( ln(P) - ln(Q) )
  • C. kB( ln(P) - ln(1) )
  • D. 0