Skip to main content
ExamWize
Sign up

FE · 3% of the exam

Thermodynamics practice questions

10 free Thermodynamics questions for the FE Environmental Exam (FE) exam, each with the correct answer and an explanation for every option.

Start the questionsFree 10-question FE quiz

What this domain covers

The smallest domain: the thermodynamics behind energy use and heat transfer in environmental systems.

Exam weight
3%
On a real exam
≈ 3 questions
In our bank
18 questions

Topics that come up most

  • First and second laws of thermodynamics
  • Ideal gas law and gas properties
  • Heat capacity and sensible and latent heat
  • Heat transfer by conduction and convection
  • Cycle and combustion efficiency

How to study it

Focus on ideal gas and heat balance calculations with consistent units. They make up most of this short domain and also come up in air quality questions.

Sample Thermodynamics questions

Try each one before opening the answer. Original questions written to the official exam objectives.

  1. Question 1

    Methane has a heating value of about 50 MJ/kg. Complete combustion of 0.5 kg of methane releases approximately:

    • A100 MJ
    • B25 MJ
    • C50 MJ
    • D2.5 MJ
    Show answer and explanation

    Answer: B) 25 MJ

    Heat released by combustion equals fuel mass times heating value: 0.5 kg × 50 MJ/kg = 25 MJ.

    • AIncorrect. This comes from dividing the heating value by the mass (50 / 0.5). Energy released is mass multiplied by heating value.
    • BCorrect. Energy = mass × heating value = 0.5 kg × 50 MJ/kg = 25 MJ.
    • CIncorrect. This is the energy from 1 kg. Only half a kilogram is burned.
    • DIncorrect. This is 10 times too small, a decimal-place error.

  2. Question 2

    A wall with an overall heat transfer coefficient U = 0.5 W/(m²·K) and an area of 100 m² has a 20-K temperature difference across it. The steady-state heat loss through the wall is closest to:

    • A50 W
    • B1 kW
    • C10 kW
    • D4 kW
    Show answer and explanation

    Answer: B) 1 kW

    Steady conduction through a wall is Q = U·A·ΔT. Here that is 0.5 × 100 × 20 = 1,000 W, or 1 kW.

    • AIncorrect. 0.5 × 100 = 50 W leaves out the 20-K temperature difference.
    • BCorrect. Q = U·A·ΔT = 0.5 W/(m²·K) × 100 m² × 20 K = 1,000 W = 1 kW.
    • CIncorrect. This is 10 times too large, which is a decimal slip such as using U = 5 instead of 0.5.
    • DIncorrect. 100 × 20 / 0.5 = 4,000 W divides by U as if it were a thermal resistance, when it should be multiplied.

  3. Question 3

    One British thermal unit (Btu) is roughly the energy needed to:

    • AMelt 1 lb of ice
    • BRaise 1 kg of water by 1 °C
    • CRaise 1 lb of water by 1 °F
    • DBoil 1 lb of water
    Show answer and explanation

    Answer: C) Raise 1 lb of water by 1 °F

    • AIncorrect. That takes about 144 Btu.
    • BIncorrect. That's about 4.18 kJ.
    • CCorrect. 1 Btu ≈ 1.055 kJ.
    • DIncorrect. That takes about 970 Btu at 212 °F.

  4. Question 4

    Burning 1,000 kg of waste with a heating value of 10 MJ/kg releases:

    • A100 MJ
    • B10,000 MJ
    • C1,010 MJ
    • D1,000 MJ
    Show answer and explanation

    Answer: B) 10,000 MJ

    • AIncorrect. Multiply, don't divide.
    • BCorrect. 1,000 × 10.
    • CIncorrect. Multiply, don't add.
    • DIncorrect. Multiply by 10 MJ/kg.

  5. Question 5

    A cooling tower rejects heat mainly through:

    • AEvaporation of a small portion of the water
    • BRadiation to the sky
    • CConduction through the tower walls
    • DChemical reaction
    Show answer and explanation

    Answer: A) Evaporation of a small portion of the water

    • ACorrect. Latent heat dominates.
    • BIncorrect. Evaporation dominates.
    • CIncorrect. Evaporation dominates.
    • DIncorrect. Evaporation dominates.

  6. Question 6

    A digester wall 0.25 m thick has k = 1 W/(m·K), area 50 m² and a 20-K temperature difference. The conduction heat loss is:

    • A0.25 kW
    • B4 kW
    • C1 kW
    • D40 kW
    Show answer and explanation

    Answer: B) 4 kW

    • AIncorrect. Divide by thickness, don't multiply.
    • BCorrect. q = kAΔT/L = 1(50)(20)/0.25 W.
    • CIncorrect. Recheck the arithmetic.
    • DIncorrect. Recheck the arithmetic.

  7. Question 7

    Air at 1 kg/s (cp = 1.005 kJ/(kg·K)) is heated by 10 K. The heat input is about:

    • A10 kW
    • B1 kW
    • C100 kW
    • D42 kW
    Show answer and explanation

    Answer: A) 10 kW

    • ACorrect. Q = ṁcpΔT = 1(1.005)(10).
    • BIncorrect. Multiply by ΔT.
    • CIncorrect. Recheck the arithmetic.
    • DIncorrect. That uses water's cp.

  8. Question 8

    How many moles of ideal gas are in 1 m³ at 101.3 kPa and 298 K?

    • A409 mol
    • B22.4 mol
    • C4.09 mol
    • D40.9 mol
    Show answer and explanation

    Answer: D) 40.9 mol

    • AIncorrect. Recheck the decimal place.
    • BIncorrect. That's liters per mole at 0 °C.
    • CIncorrect. Recheck the decimal place.
    • DCorrect. n = PV/RT = 101,300/(8.314 × 298).

  9. Question 9

    An ideal gas at constant pressure is heated from 293 K to 586 K. Its volume:

    • AQuadruples
    • BHalves
    • CStays the same
    • DDoubles
    Show answer and explanation

    Answer: D) Doubles

    • AIncorrect. The temperature ratio is 2.
    • BIncorrect. Heating expands the gas.
    • CIncorrect. V ∝ T at constant P.
    • DCorrect. Charles's law: V ∝ T at constant P.

  10. Question 10

    Evaporative coolers lower air temperature mainly by:

    • ACompressing the air
    • BUsing the latent heat of evaporating water
    • CAdding heat from a burner
    • DRemoving all moisture from the air
    Show answer and explanation

    Answer: B) Using the latent heat of evaporating water

    • AIncorrect. That heats it.
    • BCorrect. Evaporation absorbs heat from the air.
    • CIncorrect. That warms the air.
    • DIncorrect. They add moisture.

Thermodynamics: FAQs

How much of the FE exam is Thermodynamics?

Thermodynamics is 3% of the FE exam by the official exam guide's weighting, which on a 110-question form works out to roughly 3 questions. The real exam's exact split varies by form.

What does the Thermodynamics domain cover?

The smallest domain: the thermodynamics behind energy use and heat transfer in environmental systems.

How should I study Thermodynamics for FE?

Focus on ideal gas and heat balance calculations with consistent units. They make up most of this short domain and also come up in air quality questions.

Where can I practise more Thermodynamics questions?

This page has 10 free Thermodynamics questions with answers. The ExamWize FE question bank has 18 questions in this domain. Every practice exam result breaks your score down by domain, and Review Mode re-drills the questions you missed.

Other FE topics

Also: 15 free questions across all topics, the FE cheat sheet and the study guide.

Get Thermodynamics exam-ready

The full FE bank has 18 Thermodynamics questions. Timed practice exams match the real exam's length and domain weights, every result shows your score per domain, and Review Mode re-drills the questions you missed.

See the full FE practice examsTake the free diagnostic

Not affiliated with NCEES; questions are original, written from the official exam outline, and never copied from the real exam.