Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

Theme B — The Particulate Nature of Matter

B.1 Thermal Energy Transfers — IB Physics SL Revision Notes & Topical Questions

5 min read 10 parts Lesson 2 of 44 1 quiz

📚 IB Physics SL Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read
Lesson summary

B.1 Thermal Energy Transfers — IB SL Notes — IB PHYSICS SL notes: Use the particle model, specific heat capacity, specific latent heat and the three methods of thermal transfer, including black-body radiation, luminosity and apparent brightness.Solids — particles vibrate about fi…

  • What the symbols mean
  • Kelvin temperature
  • Temperature difference
  • Kinetic energy
  • Thermal equilibrium
  • Definition

Part 1 of 8Molecular model and density

Solids
  • Solids particles vibrate about fixed positions.
Liquids
  • Liquids particles are close together but free to move past one another.
Gases
  • Gases particles are far apart and move randomly at high speed.
Density
  • ρ = m/V.
    What the symbols mean: ρ = density (kg m−3 or g cm−3) · m = mass (kg) · V = volume (m3)

Part 2 of 8Temperature and kinetic energy

Kelvin temperature
  • T/K = t/°C + 273.
Temperature difference
  • Temperature difference it has the same numerical value in kelvin and degrees Celsius.
Kinetic energy
  • Kinetic energy the average random kinetic energy of the particles is Ek = (3/2)kBT.
Thermal equilibrium
  • Thermal equilibrium thermal energy flows from higher to lower temperature until the temperatures are equal.

Part 3 of 8Internal energy

Internal energy
Definition
  • Definition the sum of the random kinetic energy and the intermolecular potential energy of the particles.
Kinetic part
  • Kinetic part it depends on temperature.
Potential part
  • Potential part it depends on the separation of the particles and the state.
Change of state
  • Change of state the potential energy changes while the average kinetic energy, and so the temperature, stays constant.

Part 4 of 8Heating and changing state

Specific heat capacity c
  • Specific heat capacity c the energy needed to raise the temperature of 1 kg by 1 K, Q = mcΔT, in J kg−1 K−1.
    What the symbols mean: E, Q or q = energy transferred (J) · m = mass · c = specific heat capacity (J kg−1 °C−1; water 4.18 J g−1 °C−1) · ΔT or Δθ = temperature change (°C or K)
    • (kg; g in chemistry calorimetry)
Specific latent heat L
  • Specific latent heat L the energy needed to change the state of 1 kg at constant temperature, Q = mL, in J kg−1.
    What the symbols mean: E or Q = energy to change state without a change of temperature (J) · m = mass (kg) · L = specific latent heat (J kg−1)
  • Fusion applies to melting and freezing and vaporisation to boiling and condensing.
Insulated mixing
  • Insulated mixing energy lost by hot objects equals energy gained by cold objects.

Part 5 of 8Methods of transfer

MethodMediumMechanism
ConductionMainly solidsParticle collisions and free electrons
ConvectionLiquids and gasesBulk movement caused by density differences
RadiationNone neededElectromagnetic waves
  • Conduction rate
    • ΔQ/Δt = kAΔT/Δx, where k is the thermal conductivity.

Part 6 of 8Thermal radiation and stars

Black body
  • Black body a perfect absorber and emitter of radiation.
Stefan–Boltzmann law
  • L = σAT4.
    What the symbols mean: L = luminosity, the total power emitted (W) · σ = 5.67 × 10−8 W m−2 K−4 · r = radius of the star (m) · A = surface area (m2) · T = surface temperature (K)
Wien's law
  • λmaxT = 2.9 × 10−3 m K, so hotter bodies peak at shorter wavelengths.
Luminosity L
  • Luminosity L the total power radiated by a star.
Apparent brightness b
  • Apparent brightness b the power received per unit area at distance d, b = L/4πd2, in W m−2.
    What the symbols mean: b or F = apparent brightness (W m−2) · L = luminosity (W) · d = distance to the star (m)

Part 7 of 8Solving thermal problems

1
Identify every object that gains or loses energy.
2
Decide whether the temperature changes (mcΔT) or the state changes (mL).
3
Write energy lost by hot objects = energy gained by cold objects for an insulated system.
4
Solve, and check that the final temperature lies between the starting temperatures.

Part 8 of 8More from the specification

1
Method of Mixtures for Specific Heat
  • Dropping a preheated solid such as copper into water within an insulated calorimeter allows determination of specific heat capacity using the conservation of thermal energy equation mc delta_T(metal) = mc delta_T(water).
2
Latent Heat During Phase Transitions
  • Specific latent heat describes the energy absorbed or released per unit mass of a substance during a phase change at constant temperature, governed by Q = mL.
3
Stefan-Boltzmann Blackbody Radiation Law
  • The total radiant power emitted per unit surface area of an ideal radiator is directly proportional to the fourth power of its absolute temperature: P = e sigma A T4.
4
Planetary Albedo and Energy Equilibrium
  • Earth maintains an average thermal equilibrium where absorbed incident solar light is balanced by longwave infrared radiation emitted back into surrounding space.
5
Copper
  • Metal widely used for electrical wires.
6
Intensity
  • Power per unit area perpendicular to the wave direction.
7
Phase change
  • Change of matter from one state to another

Key terms

TermMeaning
Internal energySum of the random kinetic energy and intermolecular potential energy of the particles
Specific heat capacityEnergy per unit mass needed to raise the temperature by one kelvin
Specific latent heatEnergy per unit mass needed to change state at constant temperature
Thermal equilibriumNo net transfer of thermal energy between bodies in contact
Thermal conductivityMaterial constant relating the rate of conduction to the temperature gradient and area
Black bodyAn object that absorbs all radiation falling on it and emits the maximum possible at each wavelength
LuminosityThe total power radiated by a star
Apparent brightnessThe power received per unit area at the observer

Avoid these mistakes

1
Using °C where kelvin is needed — use kelvin in ratios and in the radiation laws.
2
Saying temperature changes during a change of state — it stays constant.
3
Adding energy to the temperature of a plateau — it goes into potential energy.
4
Using luminosity as the brightness seen from Earth — brightness falls with distance squared.
5
Treating radiated power as proportional to T — it is proportional to T4.

Last updated:

\n