By the end of this lesson, students will be able to:

• Define and use specific heat capacity (14.3.1)
• Define and use specific latent heat (14.3.2)
• Distinguish between specific latent heat of fusion and specific latent heat of vaporisation
• Apply thermal energy calculations to real-world scenarios
• Analyze energy changes during phase transitions

Students will develop their ability to:

• Use scientific terminology accurately when describing thermal properties
• Explain energy transfer processes using appropriate vocabulary
• Interpret and describe calculations involving thermal energy
• Communicate thermal physics concepts clearly in written and oral form
• Read and understand scientific texts about heat and energy

Practice with these interactive flashcards to master thermal physics terminology:

Click through each card to test your understanding of key thermal concepts!

Essential Thermal Physics Terminology

Specific Heat Capacity (c): The amount of thermal energy required to raise the temperature of 1 kg of a substance by 1 K (or 1°C).

Specific Latent Heat (L): The amount of thermal energy required to change the phase of 1 kg of a substance without changing its temperature.

Specific Latent Heat of Fusion (L_f): The thermal energy required per unit mass to change a solid to a liquid at its melting point.

Specific Latent Heat of Vaporisation (L_v): The thermal energy required per unit mass to change a liquid to a gas at its boiling point.

Phase Transition: The process of changing from one state of matter (solid, liquid, gas) to another.

Specific Heat Capacity

Specific heat capacity is a propertyсвойство/қасиет that describes how much thermal energy a substanceвещество/зат can store per unit mass per degree of temperature change. Different materials have different specific heat capacities, which explains why some materials heat up faster than others.

The formula for thermal energy transfer during temperature change is:

Q = mcΔT

Where:

• Q = thermal energy transferred (J)
• m = mass (kg)
• c = specific heat capacity (J kg⁻¹ K⁻¹)
• ΔT = temperature change (K or °C)

Specific Latent Heat

During phase transitionsфазовые переходы/фазалық ауысулар, energy is required to break or form intermolecular bondsмежмолекулярные связи/молекулааралық байланыстар without changing temperature. This energy is called latent heat because it remains hiddenскрытой/жасырын — the temperature doesn’t change even though energy is being added or removed.

The formula for latent heat energy transfer is:

Q = mL

Where:

• Q = thermal energy transferred (J)
• m = mass (kg)
• L = specific latent heat (J kg⁻¹)

Types of Latent Heat

Latent Heat of Fusion (L_f): Energy required for solid ↔ liquid transitions. Typical values: ice = 334,000 J kg⁻¹

Latent Heat of Vaporisation (L_v): Energy required for liquid ↔ gas transitions. Typical values: water = 2,260,000 J kg⁻¹

Practice Questions

1. (Easy) What is specific heat capacity?
Answer
Specific heat capacity is the amount of thermal energy required to raise the temperature of 1 kg of a substance by 1 K (or 1°C).

2. (Medium) Calculate the energy required to heat 2 kg of water from 20°C to 80°C. (c_water = 4,200 J kg⁻¹ K⁻¹)
Answer
Q = mcΔT = 2 kg × 4,200 J kg⁻¹ K⁻¹ × (80-20) K = 2 × 4,200 × 60 = 504,000 J = 504 kJ

3. (Medium) Why is more energy needed to vaporise water than to melt ice of the same mass?
Answer
Vaporisation requires breaking all intermolecular bonds to separate molecules completely, while melting only requires weakening bonds enough for molecules to move past each other. L_v > L_f for the same substance.

4. (Hard — Critical Thinking) A 0.5 kg ice cube at -10°C is heated until it becomes steam at 110°C. Calculate the total energy required. (c_ice = 2,100 J kg⁻¹ K⁻¹, L_f = 334,000 J kg⁻¹, c_water = 4,200 J kg⁻¹ K⁻¹, L_v = 2,260,000 J kg⁻¹, c_steam = 2,000 J kg⁻¹ K⁻¹)
Answer
Step 1: Heat ice from -10°C to 0°C: Q₁ = 0.5 × 2,100 × 10 = 10,500 J
Step 2: Melt ice at 0°C: Q₂ = 0.5 × 334,000 = 167,000 J
Step 3: Heat water from 0°C to 100°C: Q₃ = 0.5 × 4,200 × 100 = 210,000 J
Step 4: Vaporise water at 100°C: Q₄ = 0.5 × 2,260,000 = 1,130,000 J
Step 5: Heat steam from 100°C to 110°C: Q₅ = 0.5 × 2,000 × 10 = 10,000 J
Total: Q = 10,500 + 167,000 + 210,000 + 1,130,000 + 10,000 = 1,527,500 J = 1.53 MJ

Term Recognition Practice

1. Define specific heat capacity and give its units.
2. What is the difference between latent heat of fusion and latent heat of vaporisation?
3. Write the formula for calculating thermal energy during temperature change.
4. Write the formula for calculating energy during phase transitions.
5. Why is latent heat called «latent» (hidden)?
6. Name three examples of phase transitions.

Specific Heat Capacity and Latent Heat Explained

Related Video Resources:

• Phase Changes and Energy — Heating Curves
• Specific Heat Capacity Experiments
• Latent Heat of Fusion and Vaporization

Problem Solving with Thermal Energy Calculations

Example 1: Heating Water

Problem: How much energy is needed to heat 3 kg of water from 25°C to 95°C? (c_water = 4,200 J kg⁻¹ K⁻¹)

Example 2: Phase Change Calculation

Problem: Calculate the energy required to convert 2 kg of ice at 0°C to water at 0°C. (L_f = 334,000 J kg⁻¹)

States of Matter and Phase Changes Simulator

Use this simulation to explore how energy affects molecular motion and phase changes:

Investigation Questions:

1. What happens to molecular motion when you add energy to a solid?
2. At what point does temperature stop increasing even though you’re adding energy?
3. How does the energy required for melting compare to vaporisation?

Thermal Energy Challenge

Work in pairs or small groups to complete this interactive activity:

Group Discussion Points:

• Compare specific heat capacities of different materials and explain practical implications
• Discuss why water has such a high specific heat capacity and its environmental significance
• Design experiments to measure specific heat capacity and latent heat values
• Analyze energy efficiency in cooking and heating applications

Advanced Thermal Physics Analysis Problems

Problem 1 — Analysis

A kettle contains 1.5 kg of water at 20°C. The heating element provides 2.5 kW of power.

a) Calculate the time required to heat the water to boiling point (100°C).

b) If the kettle continues heating, how long would it take to boil away all the water?

Use: c_water = 4,200 J kg⁻¹ K⁻¹, L_v = 2,260,000 J kg⁻¹

Problem 2 — Synthesis

Design a calorimetry experiment to determine the specific heat capacity of an unknown metal. Include: equipment needed, procedure, calculations, and sources of error.

Problem 3 — Evaluation

Coastal regions have more moderate temperatures than inland areas. Using thermal physics principles, evaluate this statement and explain the role of water’s high specific heat capacity.

Problem 4 — Application

A 60 W electric heater is used to melt ice in a well-insulated container. If 0.8 kg of ice at 0°C takes 45 minutes to completely melt, calculate the specific latent heat of fusion for ice and compare to the accepted value.

Problem 5 — Critical Analysis

Steam burns are often more severe than burns from boiling water at the same temperature. Using latent heat principles, critically analyze this observation and calculate the energy difference for 10 g of steam vs 10 g of boiling water cooling to skin temperature (37°C).

Recommended Study Materials

• Save My Exams — Thermal Physics
• Physics and Maths Tutor — Thermal Physics Resources
• YouTube: Advanced Calorimetry
• PhET Energy Forms and Changes Simulation
• BBC Bitesize — Thermal Properties
• OpenStax College Physics — Heat and Temperature

Self-Assessment and Reflection

Take a moment to reflect on your learning by answering these questions:

1. Understanding: Can you clearly explain the difference between specific heat capacity and specific latent heat?
2. Application: What real-world examples can you now identify and explain using thermal physics principles?
3. Calculations: How confident do you feel solving thermal energy problems involving both temperature changes and phase transitions?
4. Connections: How does this lesson connect to other physics topics like conservation of energy?
5. Questions: What aspects of thermal physics would you like to explore further?

Learning Goals Check:

Rate your confidence (1-5 scale) on each learning objective:

• __ Defining and using specific heat capacity
• __ Defining and using specific latent heat
• __ Distinguishing between fusion and vaporisation
• __ Applying thermal energy calculations
• __ Analyzing phase change processes

Areas where you rated yourself 3 or below should be revisited using the additional resources provided.

Practical Applications:

Consider how thermal physics principles apply to:

• Cooking and food preparation
• Weather and climate patterns
• Industrial heating and cooling systems
• Energy efficiency in buildings