In simple terms
A friendly intro before the formal notes — no formulas yet.
Energy's Two Faces: Heating Up vs. Melting Down
When you add energy to a substance, it can either make it hotter (increasing kinetic energy) or change its state (increasing potential energy). This lesson explores how much energy is needed for each process.
Imagine energy is like money. Sometimes you spend money on fancy clothes (increasing your 'temperature' of style), and sometimes you spend it on a new house (changing your 'state' of living, without necessarily changing how stylish you are in that moment).
- 1
Measure Mass: How much substance do you have?
- 2
Heat It Up: Add energy, either to raise temperature or change state.
- 3
Track Change: Observe temperature change or mass of substance that changes state.
- 4
Calculate: Use specific formulas to find energy absorbed or released.
What this topic covers
The official Cambridge syllabus points this lesson works through.
- 14.3.1
Define and use specific heat capacity
- 14.3.2
Define and use specific latent heat
- 14.3.3
Distinguish between specific latent heat of fusion and specific latent heat of vaporisation
Explore the concept
Use the live diagram, PhET or GeoGebra sim, and synced steps — play it, drag controls, or tap a step.
Step-synced diagram — highlights what to look for in the simulation above.
Step 1
Measure Mass: How much substance do you have?
6 more simulations for this topic — run them in the Simulations section below
Simulations
Every simulation here runs the real model — try the steps on a card, then check what you see against the notes.
6 simulations · 4 to start with
Start herein this order — each one shows a different piece of the topic
- PhETStart here · 19702 14.1–14.3 · IB B.4
Energy Forms and Changes
Heat and cool bricks, water and iron; show the energy symbols as they transfer.
Why this one: Heat equal masses of water and iron and see the iron's temperature race ahead — lower specific heat capacity.
Try this
- On “Intro”, heat water and iron with the same flame — which thermometer rises faster?
- Put a hot brick on a cold one and show “Energy Symbols” — watch energy flow until the temperatures match.
- On “Systems”, build a chain (sun → solar panel → bulb) and trace the energy symbols.
Look for Energy flows from hot to cold until thermal equilibrium; equal energy gives unequal ΔT when c differs.
Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)
- 3JCN PhysicsStart here · 29702 14.3 · 9702 14.1 · IB B.1
Mix Ice & Water
Mix ice and water at chosen masses and temperatures; find the final temperature
Why this one: Mix ice into warm water and work out the final temperature, counting latent heat as well as mcΔT.
Try this
- Mix a small mass of ice into warm water and find the final temperature.
- Double the ice mass and compare.
- Check the energy balance: heat lost by water equals latent heat plus heat gained by melt water.
Look for Energy lost by the warm water equals the energy to melt the ice plus the energy to warm the melt water.
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
- PhETStart here · 39702 14.3 · 16.1 · IB B.1
States of Matter
Heat or cool neon, argon, oxygen or water and watch the particles melt, boil and freeze.
Why this one: Watch particles during melting: energy goes into separating them, not speeding them up, so temperature holds.
Try this
- Heat solid water slowly — the temperature stalls while the lattice breaks up.
- On “Phase Changes”, pump in gas and read pressure as you push the lid down.
- Cool a gas until it condenses — watch the particles start to cling together.
Look for During a phase change energy goes into potential energy (bonds), not kinetic — so T is constant.
Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)
- 3JCN PhysicsStart here · 49702 14.3 · IB B.1
Supercooling
Cool water below 0 C without freezing, then nucleate it; observe latent heat release
Why this one: Nucleate supercooled water and watch its temperature jump back to 0 °C as latent heat is released.
Try this
- Cool the water below 0 °C without freezing.
- Nucleate it and watch the temperature as it freezes.
Look for On nucleation the released latent heat raises the temperature back to 0 °C while the ice forms.
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
More simulations2 more on this topic — core ones first
- 3JCN PhysicsCore9702 15.3 · 9702 14.3 · 9702 14.1
Heat Transfer (gas)
Heat a gas and watch molecules speed up; relate temperature to KE
Try this
- Heat the gas and watch the molecules speed up.
- Compare the molecular speeds at two temperatures.
Look for Mean molecular KE is proportional to the absolute temperature.
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
- 3JCN Physics9702 14.3 · IB B.1
Newton's Cooling Law
Vary initial temperature and ambient temperature; watch the exponential cooling curve of a hot object
Try this
- Set a high initial temperature and watch the cooling curve to the ambient temperature.
- Lower the ambient temperature and compare how steep the curve starts.
- Set the initial temperature close to ambient and compare the shape of the curve.
Look for The rate of cooling is proportional to the temperature difference, so the curve is exponential and flattens as the object approaches ambient.
3JCN Physics Simulation by Thomas Nguyen · CC BY 4.0
Key formulas
Tap any symbol to reveal exactly what it means and its units.
Tap a symbol — great for exam definitions
Tap a symbol — great for exam definitions
Full topic notes
Formal explanation with the rigour you need for the exam.
What is Specific Heat Capacity?
Imagine trying to warm up a swimming pool compared to a teacup. Which takes more energy? The pool, of course! Specific heat capacity helps us quantify this. It's the unique amount of thermal energy required to make one kilogram of a substance just one Kelvin (or one degree Celsius) warmer, without altering its physical state.
(or )
14.3 Specific heat capacity and specific latent heat.
Recall the definition of specific heat capacity from IGCSE / SPM.
The SI unit for specific heat capacity is J kg -1 K -1 or J kg -1 o C -1.
The specific heat capacity tells us how much a substance can “absorb” thermal energy before its temperature increases.
E.g., a metallic substance like copper has less heat capacity than wood. If both substances are exposed to heat simultaneously, the copper will have a higher temperature than the wood.
Typically, a substance with a high c, will heat up or cool down slower .
Understanding Specific Latent Heat
What happens when ice melts, or water boils? The temperature stays constant during these changes of state, even though you're still adding heat! This 'hidden' energy is called specific latent heat. It's the energy needed to rearrange particles, breaking or forming bonds, rather than making them move faster.
is the heat energy transferred, in Joules (J).
is the mass of the substance that changes state, in kilograms (kg).
is the specific latent heat, with units of J kg⁻¹.
No temperature change occurs during this process.
Energy supplied increases particles' potential energy, not kinetic energy.
Fusion vs. Vaporisation: Two Forms of Latent Heat
There are two main types of specific latent heat, depending on the state transition. Specific latent heat of fusion applies when a substance melts (solid to liquid) or freezes (liquid to solid). Specific latent heat of vaporisation is for boiling (liquid to gas) or condensation (gas to liquid).
Fusion: Energy to break intermolecular bonds for melting or form them for freezing.
Vaporisation: Energy to separate particles completely for boiling or bring them closer for condensation.
(vaporisation) is generally much greater than (fusion) for the same substance.
More energy is needed to overcome intermolecular forces fully to create a gas than just to loosen them in a liquid.
Always specify whether you're referring to specific latent heat of fusion or vaporisation in your answers. They are distinct values and represent different energy requirements.
Evaporation: A Cooling Process
Evaporation is a surface phenomenon where high-energy particles escape from a liquid's surface to become gas, even below its boiling point. Because the most energetic particles leave, the average kinetic energy of the remaining liquid decreases, leading to a cooling effect. This is why sweating cools you down!
Experimental Determination & Common Errors
To find specific heat capacity or latent heat in the lab, you typically measure the energy supplied (often electrical energy, ), the mass of the substance, and either its temperature change () or the mass that undergoes a state change (). Simple in theory, but accuracy can be tricky!
Heat Capacity Experiment: Measure , (from electrical heater), . Calculate .
Latent Heat Experiment: Measure (from electrical heater), and the mass that melts/boils/condenses. Calculate .
Major Error: Heat loss to the surroundings is a common issue.
Effect of Heat Loss: Calculated 'c' or 'L' often appears higher than the true value, as not all supplied energy goes into the substance.
Improving Accuracy: Use insulation (e.g., polystyrene), polish surfaces to reduce radiation, and ensure good thermal contact.
Worked examples
See the formulas applied — reveal one step at a time, like the exam.
A 2.5 kg block of aluminium is heated, absorbing 120 kJ of energy. If its temperature rises from 20 °C to 70 °C, calculate the specific heat capacity of aluminium.
- 1
Identify knowns: kg, kJ J, K (or °C).
An immersion heater rated at 50 W is used to melt 0.030 kg of ice at 0 °C in 2 minutes. Assuming no heat loss, calculate the specific latent heat of fusion of ice.
- 1
Identify knowns: Power W, mass kg, time min s.
How it all connects
The big idea sits in the middle — tap a linked idea to explore the link.
Tap a linked idea to see how it connects back to the main topic — that connection is what examiners reward.
Glossary
Key terms for this topic — skim now; the Check step will test them.
- Specific latent heat of vaporisation
There are two main types of specific latent heat, depending on the state transition. Specific latent heat of fusion applies when a substance melts (solid to liquid) or freezes (liquid to solid). Specific latent heat of vaporisation is for boiling (liquid to gas) or condensation (gas to liquid).
- Specific heat capacity
The thermal energy needed to raise the temperature of 1 kg of a substance by 1 K (or 1 °C) without changing its state.
- SI unit for specific
Joules per kilogram per Kelvin (J kg⁻¹ K⁻¹).
- Specific latent heat
The thermal energy needed to change the state of 1 kg of a substance without changing its temperature.
- evaporation cause
High-energy particles escape from the liquid surface, reducing the average kinetic energy and temperature of the remaining liquid.
Quick check
Write your answer first, then compare it with the model one — the gap is what you would have lost.
Teach it back
If you can explain it simply, you own it — gaps here are marks you’d lose.
Teach it back
Explain this topic as if teaching a friend. We name the gaps an examiner would still dock.
Revision flashcards
Guess first, then flip — retrieval beats re-reading.
Key takeaways
Review these before you close the topic — retrieval beats re-reading.
14.3 Specific heat capacity and specific latent heat.
Recall the definition of specific heat capacity from IGCSE / SPM.
The SI unit for specific heat capacity is J kg -1 K -1 or J kg -1 o C -1.
The specific heat capacity tells us how much a substance can “absorb” thermal energy before its temperature increases.
E.g., a metallic substance like copper has less heat capacity than wood. If both substances are exposed to heat simultaneously, the copper will have a higher temperature than the wood.
Typically, a substance with a high c, will heat up or cool down slower .
Practice — then mark it
The whole point: a real Cambridge question, marked mark-by-mark.
Define specific heat capacity.
Define specific latent heat.
Extra simulations & links
PhET, GeoGebra and other curated tools — open in a new tab.
Frequently asked
Checkpoint
One marked question is worth ten re-reads — close the loop before you move on.
Reading it isn’t knowing it — prove it.
Before you move on: do 9702/41 · Q2(a) on paper, snap a photo, and get examiner-style feedback on exactly where you win and lose marks.
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