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D. Energy and Society · Thermal and Nuclear Energy

Thermal and Nuclear Energy: Unit Review

D1.1 D1.2 D2.1 D2.9 D2.10 D2.11 D3.3 D3.6 D3.7 D3.8 D3.9 D3.10 D3.11 D3.12 A1.3 A1.4 A1.5 A1.6 A1.8 A1.9 A1.10 A1.11 A1.12 A1.13 A2.1 A2.2About 40 minutes
Learning goals
  • I can explain heat, temperature and thermal energy, and the three methods of heat transfer.
  • I can solve problems with Q = mcΔT, Q = mL and heat lost = heat gained, and analyse heating and cooling curves.
  • I can describe isotopes, radioactive decay, half-life, fission and fusion.
  • I can explain how a nuclear power plant and a heat pump work, and assess their impacts on society and the environment.

Words to know

specific heat capacity (c)
Energy to raise 1 kg of a substance by 1 °C; J/(kg·°C).
latent heat (L)
Energy per kilogram absorbed or released during a change of state; J/kg.
isotopes
Atoms of the same element with different numbers of neutrons.
half-life
Time for half of the radioactive nuclei in a sample to decay.
fission / fusion
Splitting a heavy nucleus / joining light nuclei; both release energy.

Let's review!

In the first half of this unit you learned what temperature, thermal energy and heat really mean, how heat moves by conduction, convection and radiation, and how to calculate heat with Q = mcΔT and Q = mL. You measured specific heat capacity by mixing, read heating and cooling curves, and saw how heat pumps use latent heat to move heat from cold to warm.

In the second half you looked inside the nucleus: isotopes such as deuterium and tritium, alpha, beta and gamma radiation, half-life, fission and fusion, the CANDU reactor, and how nuclear and geothermal technologies affect people and the environment.

This review has a few questions from every lesson. Try each one, then press Show answer to check.

How to use this review

Do one or two sections at a time. For calculation questions, write the equation first, list the given values with units, convert grams to kilograms, and round only the final answer. For decay and fission equations, check that the top numbers and the bottom numbers both balance. For every question you get wrong, write down why (wrong equation? sign error? forgot a step of a heating curve?) and go back to that lesson's worked examples. Finish with the 10-question quiz. Use c(water) = 4180, c(ice) = 2100 J/(kg·°C), L_f = 3.34 × 10⁵ J/kg and L_v = 2.26 × 10⁶ J/kg.

Heat and temperatureT(K) = T(°C) + 273heat flows hot → coldconduction, convection, radiationHeat equationsQ = mcΔT (no state change)Q = mL (state change)Q_hot + Q_cold = 0The nucleusN = A − Z; isotopes: H, D, Tα (⁴₂He), β (⁰₋₁e), γN = N₀(½)^(t/T)Nuclear energyfission: heavy nucleus splitsfusion: light nuclei joinCANDU: heat → steam → turbine
The four big ideas of the unit and their key relationships.

Temperature, Thermal Energy and Heat

1

Convert −40 °C to kelvins.

2

A lake at 18 °C and a cup of tea at 85 °C: which has the higher temperature, and which has more thermal energy?

3

What is thermal equilibrium?

Heat Transfer: Conduction, Convection and Radiation

1

Which method of heat transfer moves energy from the Sun to Earth?

2

Why does a metal doorknob feel colder than a wooden door at the same temperature?

3

Explain how a hot-air register near the floor heats a whole room.

Specific Heat Capacity and Q = mcΔT

1

How much heat is needed to warm 0.80 kg of water from 10 °C to 60 °C?

2

A 0.50 kg block absorbs 9000 J and warms by 40 °C. Find c.

3

Why does Lake Superior keep nearby towns cooler in early summer?

Thermal Equilibrium, Mixtures and Measuring Specific Heat Capacity

1

0.25 kg of water at 80 °C is mixed with 0.75 kg of water at 20 °C. Find T_f.

2

A 0.20 kg metal at 100 °C goes into 0.30 kg of water at 20 °C; T_f = 25 °C. Find c(metal).

3

An experimental value is 418 and the accepted value is 450. Find the percent error.

Changes of State and Latent Heat

1

How much energy is needed to melt 1.5 kg of ice at 0 °C?

2

Why does the temperature stay constant while water boils?

3

Name the change of state from gas directly to solid.

012345678-20020406080100120time (min), steady heatingtemperature (°C)PQRS
Heating curve for 1 kg of ice at −20 °C heated steadily, drawn to scale. Use it for the questions in the next section.

Heating and Cooling Curves and Multi-Step Heat Problems

1

In the heating curve above, which sections are changes of state? Name them.

2

In the curve, why is S much longer than Q?

3

How much energy is needed to turn 0.10 kg of ice at −10 °C into water at 30 °C?

Heat Pumps, Refrigerators and Thermal Technologies

1

A heat pump delivers 1.5 × 10⁷ J using 5.0 × 10⁶ J of electricity. Find the COP and the heat taken from outdoors.

2

Where does the refrigerant absorb heat in a refrigerator, and by what change of state?

3

Give one benefit and one risk of a ground-source heat pump.

The Nucleus and Isotopes

1

How many protons and neutrons are in ¹³¹₅₃I?

2

Describe the nuclei of protium, deuterium and tritium.

3

Why do heavy nuclei need more neutrons than protons?

Alpha, Beta and Gamma Radiation

1

Complete: ²¹⁰₈₄Po → ²⁰⁶₈₂Pb + ___.

2

Complete: ⁹⁰₃₈Sr → ___ + ⁰₋₁e.

3

Rank α, β, γ from most to least penetrating.

4

Name the three rules for reducing radiation exposure.

Radioactive Half-Life

1

A 120 g sample has a half-life of 5 years. How much remains after 15 years?

2

Wood has 25% of its original carbon-14. Estimate its age (T = 5730 years).

3

What percentage of a sample remains after 1.5 half-lives?

Nuclear Fission and Nuclear Fusion

1

Find X: ¹₀n + ²³⁵₉₂U → ¹³⁹₅₆Ba + X + 3 ¹₀n.

2

Why do both fission and fusion release energy?

3

Give one reason fusion is not yet used to make electricity.

The CANDU Reactor: Inside a Nuclear Power Plant

1

List the energy transformations from fission to electricity.

2

A unit uses 3.3 × 10⁹ J of heat per second and delivers 1.1 × 10⁹ J of electrical energy per second. Find the waste heat per second.

3

What is the job of heavy water as a moderator?

Nuclear and Geothermal Technology and Society

1

Why does technetium-99m have to be produced continually?

2

Does irradiating food make it radioactive?

3

Why is community willingness, including that of First Nations, a key part of siting a deep geological repository?

Just for fun

A physics student tried to make a pun about half-life, but only half of it came out. Then half of that. Then half of that... The good news is, it never completely disappears.

Check your understanding

Quiz

1.

Which quantity measures the average kinetic energy of particles?

2.

Which method of heat transfer does NOT need matter?

3.

How much heat is needed to warm 2.0 kg of water by 5.0 °C?

4.

0.50 kg of water at 90 °C is mixed with 0.50 kg of water at 10 °C. The final temperature is:

5.

During a plateau on a heating curve:

6.

A heat pump with COP 4 delivers 8.0 × 10⁶ J of heat. How much electrical energy does it use?

7.

Tritium's nucleus contains:

8.

In beta decay, the atomic number of the nucleus:

9.

A radioisotope has a half-life of 4 days. What fraction remains after 12 days?

10.

In a CANDU nuclear station, about two-thirds of the reactor's heat is released to the lake because:

For parents and teachers

How to use the results: each section matches one lesson, so mistakes point to the lesson to revisit.

  • Mixing up temperature, thermal energy and heat, or Kelvin conversions → Temperature, Thermal Energy and Heat.
  • Naming the wrong method of heat transfer → Heat Transfer: Conduction, Convection and Radiation.
  • Forgetting to convert grams to kilograms or sign errors in Q = mcΔT → Specific Heat Capacity and Q = mcΔT.
  • Errors in mixture problems or percent error → Thermal Equilibrium, Mixtures and Measuring Specific Heat Capacity.
  • Using Q = mcΔT during melting or boiling, or mixing up L_f and L_v → Changes of State and Latent Heat.
  • Missing steps in ice-to-steam problems or misreading graphs → Heating and Cooling Curves and Multi-Step Heat Problems.
  • Thinking a fridge makes cold, or COP confusion → Heat Pumps, Refrigerators and Thermal Technologies.
  • Counting protons and neutrons, isotopes of hydrogen → The Nucleus and Isotopes.
  • Unbalanced decay equations or mixed-up properties of α, β, γ → Alpha, Beta and Gamma Radiation.
  • Subtracting instead of halving, or calculator errors with exponents → Radioactive Half-Life.
  • Forgetting neutrons in fission equations; confusing fission and fusion → Nuclear Fission and Nuclear Fusion.
  • Incomplete energy chains or misunderstanding waste heat → The CANDU Reactor: Inside a Nuclear Power Plant.
  • One-sided opinions without evidence → Nuclear and Geothermal Technology and Society.

The sibling unit Work, Energy and Power covers work, kinetic and potential energy, power, efficiency of energy sources and E = mc²; those topics are not reviewed here.