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 and synced steps — play it or tap a step card to walk through.
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
Try to recall each definition before you reveal it.
Quick check
Answer in your head first — then tap to check. No pressure.
Revision flashcards
Flip the card. Test yourself before the exam.
Define 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.
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.
Mark a past-paper question on this topic
Mark a past-paper question on this topic
Extra simulations & links
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Frequently asked
Checkpoint
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Reading it isn’t knowing it — prove it.
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