What is Thermal Physics and why is it important in the IB MYP Science curriculum?

Thermal Physics is the study of heat, temperature, and the transfer of energy. It is important in the IB MYP Science curriculum because it helps students understand how energy is transferred and transformed in different systems, which is fundamental to many scientific processes and real-world applications.

How does heat transfer occur between objects?

Heat transfer occurs through three main processes: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact, convection involves the movement of fluids (liquids or gases), and radiation is the transfer of energy through electromagnetic waves. Understanding these processes is crucial for explaining phenomena in Thermal Physics.

What is the difference between temperature and heat in Thermal Physics?

Temperature is a measure of the average kinetic energy of the particles in a substance, while heat is the total energy transferred between substances due to a temperature difference. In Thermal Physics, it's important to distinguish between these concepts to accurately describe energy changes in systems.

Why is specific heat capacity an important concept in Thermal Physics?

Specific heat capacity is the amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius. It is important in Thermal Physics because it helps predict how different materials respond to heat, which is essential for understanding energy efficiency and thermal management in various applications.

How do the laws of thermodynamics apply to Thermal Physics?

The laws of thermodynamics are fundamental principles that describe how energy is transferred and conserved in systems. In Thermal Physics, these laws help explain how energy flows, how systems reach thermal equilibrium, and the limits of energy conversion processes. They are crucial for understanding the behavior of systems in both natural and engineered environments.

Why is "Saying 'this object has lots of heat'." a common mistake in Thermal Physics?

Why it happens: In everyday English heat and temperature are used interchangeably. How to avoid it: Heat is energy IN TRANSIT. Objects HAVE internal energy and HAVE temperature — they do not 'have' heat.

Why is "Believing temperature continues to rise during a state change." a common mistake in Thermal Physics?

Why it happens: Energy is being supplied, so students assume temperature must increase. How to avoid it: During melting or boiling the energy goes into bond-breaking, not particle KE. Temperature stays constant until the change of state is complete.

Why is "Mixing up specific heat capacity and specific latent heat." a common mistake in Thermal Physics?

Why it happens: Both involve mass and energy. How to avoid it: c is used when TEMPERATURE changes (and state doesn't). L is used when STATE changes (and temperature doesn't).

Heat, light and soundIB MYP Sciences (Years 1-5)

Thermal Physics

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Thermal Physics — IB MYP Sciences: temperature, thermal energy, specific heat capacity and latent heat

Heat and temperature look the same in everyday speech but mean very different things in science. This MYP Sciences note untangles them, covers specific heat capacity (why a swimming pool takes ages to warm up) and specific latent heat (why a kettle plateaus at 100 °C).

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Distinguish between temperature, heat and internal energy.
MYP Sciences A — State and use ΔE = mcΔθ and E = mL.
MYP Sciences B — Plan an investigation to find the specific heat capacity of a metal.
MYP Sciences C — Interpret heating and cooling curves: identify state-change plateaus and gradient sections.
MYP Sciences D — Evaluate why water's high specific heat capacity matters for climate and biology.

Temperature vs heat vs internal energy

Temperature tells you how hot. Heat is energy transferred. Internal energy is the total energy of all particles.

Temperature is a measure of the average kinetic energy of particles. Two objects can be at the same temperature but contain very different amounts of total energy (a bucket vs a swimming pool).

Heat is energy transferred due to a temperature difference. You can't say "this object has 50 J of heat" — heat is a process, not a stored quantity.

Internal energy is the TOTAL kinetic + potential energy of all particles in a substance. A swimming pool at 20 °C has much more internal energy than a cup of tea at 20 °C, despite the same temperature, because there are far more particles.

Heat flows naturally from a hotter object to a colder one until both reach the same temperature — thermal equilibrium.

Temperature ≈ average KE of particles.
Heat = energy in transit due to a temperature difference.
Internal energy = total energy of all particles.
Heat flows from hot to cold until thermal equilibrium.

Specific heat capacity

How much energy a material needs to warm up.

Specific heat capacity (c) is the energy needed to raise the temperature of 1 kg of a material by 1 °C (or 1 K — the same size):

$\Delta E = m \, c \, \Delta\theta$

with E in J, m in kg, c in J/(kg·K), Δθ in °C or K.

Some values:

Substance	c (J/(kg·K))
Water	4 200
Vegetable oil	1 800
Aluminium	900
Copper	380
Lead	130

Water's c is unusually high — it takes a lot of energy to warm up and gives a lot of energy back when it cools. This is why coastal regions have milder climates than inland ones, and why a hot-water bottle stays warm for hours.

Worked example. How much energy does it take to heat 0.50 kg of water from 20 °C to boiling at 100 °C?

ΔE = mcΔθ = 0.50 × 4 200 × (100 − 20) = 0.50 × 4 200 × 80 = 168 000 J = 168 kJ.

ΔE = mcΔθ. Bigger c → harder to heat up.
Water has c = 4 200 J/(kg·K) — very high.
High c keeps coastal climates stable.

Specific latent heat

Energy to change state — without any temperature change.

When ice melts to water, or water boils to steam, you supply energy but the temperature doesn't change. The energy goes into breaking the bonds between particles, freeing them to flow (liquid) or escape entirely (gas).

Specific latent heat (L) is the energy needed to change the state of 1 kg of a substance at its transition temperature:

$E = m \, L$

Two kinds:

Specific latent heat of fusion (Lf): solid ↔ liquid. For ice/water: ~334 kJ/kg.
Specific latent heat of vaporisation (Lv): liquid ↔ gas. For water/steam: ~2 260 kJ/kg.

Lv is always larger than Lf because turning a liquid into a gas needs to break ALL the bonds, not just loosen them.

Heating curve for water — the plateaus at 0°C and 100°C are where the latent heat is being absorbed.

E = mL for state changes.
Fusion: solid ↔ liquid (~334 kJ/kg for ice).
Vaporisation: liquid ↔ gas (~2 260 kJ/kg for water).
Heating curves have plateaus at the state-change temperatures.

How it’s examined

Criterion A tests definitions (temperature vs heat vs internal energy) and the two formulae. Criterion C presents a heating curve and asks you to identify each section, or gives data and asks you to calculate c or L.

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

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Step-by-step worked examples — Thermal Physics

Step-by-step solutions to past-paper-style questions on thermal physics, written exactly the way a tutor would explain them at the board.

1Heating water
Getting started• specific heat capacity
Question
How much energy is needed to heat 0.20 kg of water from 25 °C to 95 °C? (c = 4 200 J/(kg·K).)
Step-by-step solution
1. Step 1
  Δθ = 95 − 25 = 70 °C.
2. Step 2
  ΔE = mcΔθ = 0.20 × 4 200 × 70.
3. Step 3
  ΔE = 58 800 J ≈ 58.8 kJ.
Answer
≈ 58.8 kJ.
2Finding specific heat capacity
Building confidence• specific heat capacity
Question
A 500 W heater raises 1.0 kg of oil from 20 °C to 40 °C in 60 s. Calculate the specific heat capacity of the oil.
Step-by-step solution
1. Step 1
  Energy supplied = P × t = 500 × 60 = 30 000 J.
2. Step 2
  Rearrange ΔE = mcΔθ → c = ΔE / (mΔθ).
3. Step 3
  c = 30 000 / (1.0 × 20) = 1 500 J/(kg·K).
Answer
c ≈ 1 500 J/(kg·K).
3Melting ice
Building confidence• latent heat
Question
How much energy is needed to melt 0.30 kg of ice at 0 °C? L_fusion = 334 kJ/kg.
Step-by-step solution
1. Step 1
  Use E = mL.
2. Step 2
  E = 0.30 × 334 000 = 100 200 J ≈ 100 kJ.
Answer
≈ 100 kJ.
4Reading a heating curve
Stretch• heating curve
Question
On a heating curve for water there are two flat sections. What is happening at each, and why does the temperature not change?
Step-by-step solution
1. Step 1
  The first plateau is at 0 °C — ice melting to water.
2. Step 2
  The second plateau is at 100 °C — water boiling to steam.
3. Step 3
  Temperature is constant because the energy supplied is being used to break bonds between particles (latent heat), not to increase particle KE.
Answer
First plateau: melting (latent heat of fusion). Second plateau: boiling (latent heat of vaporisation). Temperature stays constant because energy is being used to break bonds, not to raise temperature.

Key Formulae — Thermal Physics

The formulae you need to memorise for thermal physics on the IB MYP Sciences paper, with every variable defined in plain English and a note on when to use it.

Heating without state change
$ΔE = m × c × Δθ$
$ΔE$
energy supplied (J)
$m$
mass (kg)
$c$
specific heat capacity (J/(kg·K))
$Δθ$
temperature change (°C or K)
When to use
Use whenever temperature changes but state does NOT change.
Change of state
$E = m × L$
$E$
energy (J)
$m$
mass (kg)
$L$
specific latent heat (J/kg)
When to use
Use during melting/freezing or boiling/condensing.

Key Definitions and Keywords — Thermal Physics

Definitions to memorise and the exact keywords mark schemes credit for thermal physics answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.

Temperature
Examiner keyword
A measure of the average kinetic energy of particles in a substance. Units: K or °C.
Heat
Examiner keyword
Energy transferred from a hotter to a colder object because of a temperature difference. Not the same as internal energy.
Internal energy
Examiner keyword
The total kinetic and potential energy of all the particles in a substance.
Specific heat capacity (c)
Examiner keyword
The energy needed to raise the temperature of 1 kg of a substance by 1 K. Unit: J/(kg·K).
Specific latent heat (L)
Examiner keyword
The energy needed to change the state of 1 kg of a substance at its transition temperature. Unit: J/kg.
Thermal equilibrium
The state where two objects in contact have reached the same temperature, so no net heat flows between them.

Common Mistakes and Misconceptions — Thermal Physics

The traps other students keep falling into on thermal physics questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.

✕Saying 'this object has lots of heat'.
Why it happens
In everyday English heat and temperature are used interchangeably.
How to avoid it
Heat is energy IN TRANSIT. Objects HAVE internal energy and HAVE temperature — they do not 'have' heat.
✕Believing temperature continues to rise during a state change.
Why it happens
Energy is being supplied, so students assume temperature must increase.
How to avoid it
During melting or boiling the energy goes into bond-breaking, not particle KE. Temperature stays constant until the change of state is complete.
✕Mixing up specific heat capacity and specific latent heat.
Why it happens
Both involve mass and energy.
How to avoid it
c is used when TEMPERATURE changes (and state doesn't). L is used when STATE changes (and temperature doesn't).

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

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Thermal Physics — frequently asked questions

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Thermal Physics

Short Study Notes in the form of Slides

Short Study Notes — Thermal Physics

Detailed Notes

What you’ll learn

How it’s examined

1Heating water

2Finding specific heat capacity

3Melting ice

4Reading a heating curve

Heating without state change

Change of state

Temperature

Heat

Internal energy

Specific heat capacity (c)

Specific latent heat (L)

Thermal equilibrium

✕Saying 'this object has lots of heat'.

✕Believing temperature continues to rise during a state change.

✕Mixing up specific heat capacity and specific latent heat.

Practice questions

Past paper style quiz

Assess your understanding

Thermal Physics — frequently asked questions