Physics · Unit 14

Heat and Thermodynamics

Temperature, heat and energy flow

Temperature and heat are not the same thing, and thermodynamics does not really work until that distinction is solid: one is a measure of average particle energy, the other is energy in transit.

The unit covers thermometers and temperature scales, conduction, convection and radiation, specific and latent heat, the gas laws, and the laws of thermodynamics.

This unit breaks down into 20 short steps and 118 questions, starting at difficulty 2 and building to 3. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 20
Questions: 118
Difficulty: 2-3

What this unit covers

Specific and Latent Heat
Conduction, Convection, Radiation
Temperature and Thermometers
Laws of Thermodynamics
Gas Laws

Where this fits

Needs Energy and Its Forms and States of Matter and Density.

Where people slip

A bath at forty degrees contains far more thermal energy than a spark at a thousand. Temperature is intensive and energy is extensive, and confusing them makes heat questions unanswerable.

How the unit is structured

Heat and Thermodynamics runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 2 and climb to 3 as you progress.

Step 1 · easierStep 20 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 118 in the unit altogether.

Conduction, Convection, Radiation

Fact or fibLevel 2
1. A vacuum flask keeps a drink hot by reducing conduction, convection and radiation.
Answer: True
The vacuum stops conduction and convection while shiny walls reflect radiation, so all three transfer paths are limited.
Fill the blankLevel 2
2. In ____, heat moves through a solid by particle collisions without the material itself flowing.
- conductioncorrect
- convection
- radiation
- evaporation
Conduction transfers heat as vibrating particles collide and pass energy along, common in metals.
Match the pairsLevel 2
3. Match each heat term to its correct description.
Answer: Conduction = Heat through a metal by direct contact; Convection = Currents in heated liquids and gases; Radiation = Infrared waves through empty space; Insulator = A material that slows heat flow
Conduction is contact transfer, convection is fluid currents, radiation is infrared waves, and an insulator slows heat flow.
Build the sentenceLevel 3
4. Build the reason a vacuum flask keeps a drink hot.
Answer: a vacuum gap prevents conduction and convection
A vacuum has no particles, so it blocks conduction and convection, while silvered walls reduce radiation.
Choose all that applyLevel 3
5. Which statements about thermal radiation are correct?
- It can travel through a vacuumcorrect
- A perfect black body is the best possible emitter and absorbercorrect
- The power radiated depends on the fourth power of the absolute temperaturecorrect
- It needs particles to carry the energy along
Thermal radiation is electromagnetic, needs no medium, and by Stefan's law its power is proportional to absolute temperature to the fourth power.
Guess the numberLevel 3
6. The Sun's surface is about 5800 K. Using Wien's law lambda_max = b/T with b = 2.9e-3 m.K, at roughly what wavelength does its radiation peak? Answer in nanometres.
Answer: 500 nm
lambda_max = 2.9e-3 / 5800 = 5.0e-7 m = 500 nm, near the middle of visible light.

Gas Laws

Fact or fibLevel 2
7. When using the gas laws, temperature must be measured in kelvin, not degrees C.
Answer: True
Gas law calculations use absolute (kelvin) temperature because the relationships are proportional to it.
Fill the blankLevel 2
8. According to ____'s law, halving the volume of a gas at constant temperature doubles its pressure.
- Boylecorrect
- Charles
- Newton
- Ohm
This inverse pressure-volume relationship is Boyle's law.
Guess the numberLevel 2
9. A gas at 100 kPa is squeezed to half its volume at constant temperature. Using Boyle's law, what is its new pressure in kPa?
Answer: 200 kPa
Boyle's law gives P1 x V1 = P2 x V2, so halving the volume doubles the pressure to 200 kPa.
Match the pairsLevel 2
10. Match each gas law to the relationship it describes.
Answer: Boyle's law = Pressure vs volume at constant temperature; Charles's law = Volume vs temperature at constant pressure; Gay-Lussac's law = Pressure vs temperature at constant volume; Avogadro's law = Volume vs amount of gas
Each gas law links two properties while a third is held constant.
Build the sentenceLevel 3
11. State the combined gas law for a fixed mass of ideal gas.
Answer: pressure times volume over temperature is constant
The combined gas law says pV/T stays constant for a fixed mass of ideal gas.
Choose all that applyLevel 3
12. Which of these are assumptions of the kinetic theory of an ideal gas?
- Collisions between molecules are perfectly elasticcorrect
- Molecule volume is negligible compared with the containercorrect
- The molecules are in constant random motioncorrect
- There are strong attractive forces between molecules
An ideal gas is modelled as point-like molecules in constant random motion, with perfectly elastic collisions and negligible intermolecular forces.

Laws of Thermodynamics

Choose all that applyLevel 2
13. Which of these statements about the second law of thermodynamics are correct? Select all that apply.
- Heat flows spontaneously from hot to coldcorrect
- The entropy of an isolated system tends to increasecorrect
- A heat engine cannot be 100 percent efficientcorrect
- Heat flows from cold to hot with no work done
Heat flows hot to cold on its own, entropy of an isolated system increases, and no engine can be perfectly efficient; heat does not flow cold to hot without work.
Fact or fibLevel 2
14. The third law of thermodynamics says you can reach absolute zero in a finite number of steps.
Answer: False
The third law states that absolute zero cannot be reached in a finite number of steps.
Fill the blankLevel 2
15. The second law of thermodynamics says the ____, or disorder, of an isolated system tends to increase.
- entropycorrect
- enthalpy
- pressure
- density
Entropy is the measure of disorder, and it tends to increase in an isolated system.
Match the pairsLevel 2
16. Match each law of thermodynamics to its simple statement.
Answer: Zeroth law = Objects in thermal equilibrium share a temperature; First law = Energy is conserved; Second law = Entropy tends to increase; Third law = Absolute zero cannot be reached
The zeroth law defines temperature, the first is energy conservation, the second is rising entropy, and the third says absolute zero cannot be reached.
Build the sentenceLevel 3
17. Arrange the words to state the first law of thermodynamics (delta U = Q - W).
Answer: change in internal energy equals heat added minus work done
The first law says the change in internal energy equals the heat added minus the work done by the system.
Guess the numberLevel 3
18. A heat engine takes in 800 J of heat and does 200 J of useful work each cycle. What is its efficiency as a percentage?
Answer: 25 percent
Efficiency = useful work / energy input = 200 / 800 = 0.25 = 25 percent.

Specific and Latent Heat

Build the sentenceLevel 2
19. Arrange the words to describe what happens to ice as it melts.
Answer: Ice absorbs latent heat when it melts
Ice takes in latent heat of fusion as it melts, which breaks the bonds holding the solid together.
Fill the blankLevel 2
20. ____ heat is absorbed when a liquid boils into a gas, with no rise in temperature.
- Latentcorrect
- Specific
- Radiant
- Kinetic
Latent heat of vaporisation is absorbed during boiling to separate the particles into a gas.
Guess the numberLevel 2
21. About what is the specific heat capacity of water, in joules per kg per degree C?
Answer: 4200 J/kg/degrees C
Water has a high specific heat capacity of about 4200 J per kg per degree C.
Match the pairsLevel 2
22. Match each change of state to what happens to the substance.
Answer: Melting = Solid to liquid; Boiling = Liquid to gas; Condensing = Gas to liquid; Freezing = Liquid to solid
Melting is solid to liquid, boiling is liquid to gas, condensing is gas to liquid, and freezing is liquid to solid.
Multiple choiceLevel 2
23. Latent heat is the energy absorbed or released during what?
- A change of state, with no temperature change
- A steady rise in temperature
- A chemical reaction only
- A drop in the mass of the substance
Latent heat is exchanged during a change of state, such as melting or boiling, with no change in temperature.
Fact or fibLevel 3
24. Water has a much higher specific heat capacity than iron.
Answer: True
Water's specific heat is about 4200 J/kg/degrees C compared with iron's roughly 450, so water heats and cools slowly.

Temperature and Thermometers

Fill the blankLevel 2
25. Absolute zero, the coldest temperature possible, is 0 ____.
- kelvincorrect
- degrees Celsius
- degrees Fahrenheit
- joules
Absolute zero is 0 kelvin, equal to about -273 degrees C.
Guess the numberLevel 2
26. At normal sea-level pressure, at what temperature in degrees C does pure water boil?
Answer: 100 degrees C
Water boils at 100 degrees C at standard atmospheric pressure.
Match the pairsLevel 2
27. Match each temperature landmark to its value.
Answer: Water freezes (Celsius) = 0 degrees C; Water boils (Celsius) = 100 degrees C; Absolute zero (Kelvin) = 0 K; Human body temperature = 37 degrees C
Water freezes at 0 degrees C and boils at 100 degrees C, absolute zero is 0 K, and human body temperature is about 37 degrees C.
Multiple choiceLevel 2
28. What does the temperature of an object actually measure?
- The average kinetic energy of its particlescorrect
- The total number of particles it contains
- The total mass of the object
- How much light the object gives off
Temperature is a measure of the average kinetic energy of the particles in a substance.
Odd one outLevel 2
29. Which of these is the odd one out because it is NOT a temperature scale?
- Celsius
- Kelvin
- Fahrenheit
- Joulecorrect
Celsius, Kelvin and Fahrenheit are temperature scales, but the joule is a unit of energy.
Fact or fibLevel 3
30. On the absolute (Kelvin) temperature scale, negative temperatures are impossible.
Answer: True
0 K is the lowest possible temperature, so thermodynamic (Kelvin) temperatures are always zero or positive.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 15 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Listen and choose
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sort into groups
Spell it
True or false
Type the answer

Practise Heat and Thermodynamics

118 questions across 20 steps. Start with step one and crawl at your own pace.

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Read about Heat and Thermodynamics

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

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