IB Thermodynamics Test

Mock Thermodynamics Test:

Get the Document: Misc-MockTest.pdf

1. (a) 0.164 moles of an ideal monatomic gas is in a container of volume 1.30x10^-3 m³,

with a pressure of 9.20x10⁵ Pa.

(i) Calculate the temperature of the gas
[878 K]

(ii) Calculate in J the internal energy of the gas
[1794 J]

(b) The gas is expanded very rapidly so that the pressure is 3.20x10⁵ Pa

(i) Explain why this process would be adiabatic
[???]

(ii) Calculate the new volume of the gas
[2.45x10^-3 m³]

(iii) Calculate the new temperature of the gas
575 K]

2. The pressure volume (pV) diagram shows a cycle ABCA of a heat engine. The working substance is 0.850 moles of an ideal gas. At A the pressure of the gas is 12.0x10⁵ Pa, and the volume is 1.00x10^-3 m³.

(a) For the isobaric expansion AB

(i) Calculate the temperature at A and B
[170. K, 680. K]

(ii) Calculate the work by the gas
[+3600 J]

(iii) Calculate the change in internal energy of the gas
[+5400 J]

(iv) Calculate the thermal energy that flows into the gas
[+9000 J]

(b) Calculate the thermal energy that leaves the gas for process BC
[-5400]

(c) The work done on the gas during the isothermal compression CA is 1664 J

(i) Show using data from the graph that process CA is isothermal
[pV = pV...]

(ii) Justify why the thermal energy lost during the compression CA is 1664 J
[Q=ΔU+W]

(iii) Calculate the change in entropy of the gas for the isothermal compression CA
[-9.79 J/K]

(d) Calculate the efficiency of the engine
[0.215]

3. The P-V diagram of the Carnot cycle ABCDA for a monatomic ideal gas operating with a Carnot efficiency of 0.370

(a) On the diagram label each process either ("Isothermal" or Adiabatic") and either ("Expansion" or "Compression")

(b) The low temperature is 345 K. Calculate the high temperature. Label these temperatures on the graph above. Label also the processes where no heat flows, and those there heat either flows into or out of the gas
[548 K]

(c) During process CD, 1280 J of heat flow out of the gas.

(i) Calculate the useful work done by the entire cycle
[752 J]

(ii) Calculate the heat that must flow into the gas in process AB
[2032 J]

4. A planet with an atmosphere is 1.80x10¹¹ m from a star with a radius of 9.50x10⁸ m and a surface temperature of 6250 K. The atmosphere of the planet has an albedo of 0.210.

(a) Show that the intensity of the radiation incident on the upper atmosphere is 2410 Wm^-2
[2409.9 Wm^-2]

(b) Calculate the average intensity spread out over the entire surface of the planet
[476 Wm^-2]

(c) Calculate the radiative equilibrium temperature assuming that the atmosphere were

transparent to IR wavelengths of light
[303 K]

(d) Calculate the peak black body wavelength radiated by the planet and the star. Also

state which part of the electromagnetic spectrum each wavelength belongs to. [9.58 μm, 464 nm]

(e) With reference to the wavelengths of the incident and radiated energy, explain how the surface of the planet could be warmer than the value you calculated in (c)

This is what is on the real test:

Question 1 - 6 marks (Easy?)

An ideal monatomic gas has a certain volume, temperature, and pressure

Calculate the moles of gas present-Ideal gas law (Like W13 #5 only easier)
Calculate the internal energy-Study M182-2 #2 (a)(iii) (Like W15B #1)

The gas is rapidly expanded or compressed to a different volume

Explain why a rapid change in volume would be adiabatic-Notes from lecture/Google it
Calculate the new pressure of the gas-Study M173-2 #9 (a)(ii) (Like W15B #10)
Calculate the new temperature of the gas-Study M173-2 #9 (a)(ii)

Very much like M18-2-1 #2 and M18-2-2 #2 (only the change is adiabatic, not isothermal)

Question 2 - 13 marks (Hard)

The Pressure volume diagram shows a cycle ABCA of a heat engine. The working substance is a certain number of moles of an ideal monatomic gas

at point A the gas has a certain pressure and volume, and the work done by the isothermal process is a certain amount

Using data from the graph, show that process XX is isothermal
Justify why the thermal energy supplied during the process XX is ###
Calculate the temperature at X
Calculate the change in entropy for the isothermal process

For the isobaric process XX

Calculate the work done by the gas
Calculate the change in internal energy of the gas
Calculate the thermal energy that flows into/out of the gas
Calculate the thermal energy that flow into /out of the gas for process XX
Calculate the efficiency of the engine

Study SPEC-3-0 #9 for this question, as well as M17-3-2 #9 and all the other Thermodynamics questions

Question 3 - 8 Marks (Easy)

The P-V diagram of the Carnot cycle ABCDA for a monatomic ideal gas operating between a certain high and low temperature is shown below

On the diagram label each process either "Isothermal" or "Adiabatic" and either "Expansion" or "Compression"

Calculate the Carnot Efficiency of the engine (Like W15B #37a)

If the heat flow in is a certain amount

Calculate the work done in a cycle (Like W15B #37b)
- Calculate the heat wasted by the cycle (Like W15B #37c)

These questions are just like those on 15.2. Do memorize all the parts of the Carnot Cycle, know what isothermal and adiabatic mean.

Question 4 - 8 Marks (Easy - but you'd better study this)

A planet with an atmosphere is a certain distance from a star with a certain peak black body wavelength. The radiation intensity striking the upper atmosphere of the planet is a certain amount and the albedo of the atmosphere is a certain amount.

Show that the average intensity incident over the entire surface of the planet is a certain amount (Like W14B #20,21)
Calculate the equilibrium temperature of the surface of the planet (Like W14B #22, 23)
Calculate the peak black body wavelength radiated by the planet (Like W14B #5, 6)
With reference to the wavelengths incident and radiated, explain how the surface of the planet could be warmer than the value you calculated (From your notes on the Greenhouse Effect noteguide - be able to make the argument I make when I explain how the Greenhouse Effect works)

Very much like M16-2-0 #9 from Heat and Energy questions:

M16-2-0 #9 - The Sun
Video | Question | Markscheme

Do a careful job reviewing the Greenhouse Effect noteguide, and the radiative heat transfer noteguide, as well as the Wien displacement law

Folks who did not do IB Physics last year - There is some stuff to catch up on:

Look at the IB Question above (M16-2-0 #9 - The Sun) work through it

Go to the Heat Unit and catch these flips:

14I. Understand Black Body Radiation and the Wien Displacement law.
14J. Solve problems with radiative heat transfer.
14K. Solve problems with Albedo.
14L. Understand the greenhouse effect.