IB Physics: Thermal Physics Practice
IB Physics — Thermal Physics Practice
16 MCQ practice problems covering core IB Physics thermal physics content, from temperature scales to molecular kinetic theory and ideal gas behaviour.
Practice Questions
Intuition
For gas law problems, always check which variables change and which stay constant. If temperature is constant, use Boyle’s law (p₁V₁ = p₂V₂). If pressure is constant, use Charles’s law (V₁/T₁ = V₂/T₂). For calorimetry problems, remember that energy lost by the hot substance equals energy gained by the cold substance (assuming no losses): m₁c₁ΔT₁ = m₂c₂ΔT₂. Always convert temperature to Kelvin for gas law calculations — this is the single most common error.
Why it matters: Thermal physics problems test your ability to apply the ideal gas law, specific heat capacity, and latent heat in combination. These concepts are essential for understanding engines, weather systems, and material behaviour at different temperatures. These practice questions range from basic temperature conversions to complex calorimetry problems.
Worked Example
Question: 0.5 kg of water at 80°C is mixed with 0.2 kg of ice at 0°C. What is the final temperature? (c_water = 4200 J/kg°C, L_fusion = 3.34 × 10⁵ J/kg)
Solution: Energy lost by water = energy gained by ice. The ice must first melt (Q = mL) then warm up (Q = mcΔT). Let final temperature be T. Energy lost by water: 0.5 × 4200 × (80 − T). Energy gained by ice: (0.2 × 3.34 × 10⁵) + (0.2 × 4200 × T). Solving: 0.5 × 4200 × (80 − T) = 0.2 × 3.34 × 10⁵ + 0.2 × 4200 × T. This gives T ≈ 26.7°C.
Common Mistakes
- Using Celsius instead of Kelvin in gas law calculations. The ideal gas law requires absolute temperature. A common trap is a question that gives temperature in °C — always convert first (K = °C + 273).
- Forgetting that during a phase change, the temperature stays constant even though heat is still being added. Students often apply Q = mcΔT during a phase change and get confused when ΔT = 0. Use Q = mL instead.
- Confusing specific heat capacity with specific latent heat. The first (c) is used when temperature changes: Q = mcΔT. The second (L) is used during phase changes: Q = mL. They describe fundamentally different processes.
- Forgetting that the internal energy of an ideal gas depends only on temperature. Changing volume at constant temperature (isothermal process) does not change the internal energy — all the heat goes into work done.
Cross-References
- Kinematics: Kinematics describes particle motion, and thermal physics explains how molecular motion relates to temperature.
- Mechanics: Mechanics covers energy conservation, which underpins the first law of thermodynamics and heat transfer.
- Waves: Waves transfer energy, and thermal radiation is a form of electromagnetic wave emission.
- Electricity: Electrical resistance increases with temperature, and internal resistance causes batteries to heat up.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.