NCERT Solutions for Class 11 Physics Chapter 11 – Thermal Properties of Matter
Chapter 11 of Class 11 Physics, Thermal Properties of Matter, forms the foundation of thermal physics and bridges everyday experiences of hot and cold with precise scientific concepts. Students begin by understanding temperature as a measure of the degree of hotness and its distinction from heat — which is energy in transit. The chapter explains temperature scales (Celsius, Fahrenheit, Kelvin) and how thermometers work. A significant portion covers thermal expansion of solids, liquids, and gases — the phenomenon responsible for rail gaps, bimetallic strips, mercury thermometers, and the anomalous expansion of water. The concept of specific heat capacity and the calorimetry principle (heat lost = heat gained) are essential for solving numerical problems involving temperature changes and state transitions. Students also explore latent heat — the energy required to change the state of matter without temperature change — crucial for understanding processes like melting, boiling, and condensation. The three modes of heat transfer — conduction, convection, and radiation — are studied in detail, along with Fourier's Law, Newton's Law of Cooling, and Stefan-Boltzmann Law. These concepts are fundamental to CBSE board exams and competitive entrance examinations.
NCERT Solutions PDF – Class 11 Physics Chapter 11 (All Exercises)
Complete solutions to all exercises covering temperature scales, thermal expansion, calorimetry, latent heat, and heat transfer. Solved as per the latest CBSE/NCERT curriculum.
Important Formulas – Chapter 11: Thermal Properties of Matter
| Formula | Expression | Description |
|---|---|---|
| Temperature Conversion | T_K = T_C + 273.15 | Celsius to Kelvin; absolute zero = 0 K |
| Linear Thermal Expansion | ΔL = α L₀ ΔT | α = coefficient of linear expansion (K⁻¹) |
| Area Expansion | ΔA = β A₀ ΔT; β = 2α | β = coefficient of area (superficial) expansion |
| Volume Expansion | ΔV = γ V₀ ΔT; γ = 3α | γ = coefficient of volume (cubical) expansion |
| Heat Absorbed/Released | Q = mcΔT | m = mass, c = specific heat capacity, ΔT = temp change |
| Calorimetry Principle | m₁c₁ΔT₁ = m₂c₂ΔT₂ | Heat lost by hot body = heat gained by cold body |
| Latent Heat | Q = mL | L = latent heat; no temperature change during phase transition |
| Fourier's Law (Conduction) | H = kA(T₁−T₂)/d | k = thermal conductivity; d = thickness; unit: W/m·K |
| Newton's Law of Cooling | dT/dt = −k(T − T₀) | Rate of cooling ∝ excess temperature over surroundings |
| Stefan-Boltzmann Law | P = σεAT⁴ | σ = 5.67×10⁻⁸ W/m²K⁴; ε = emissivity (0 to 1) |
| Wien's Displacement Law | λ_max · T = 2.898 × 10⁻³ m·K | Peak wavelength of radiation shifts with temperature |
Subtopics Explained – Chapter 11: Thermal Properties of Matter
Temperature and Thermometers
Temperature is the physical quantity that determines the direction of heat flow. Different thermometric properties (expansion of mercury, resistance change in metals, thermoelectric EMF) form the basis of different thermometers. The absolute (Kelvin) scale is the SI scale, where 0 K = −273.15°C is the lowest possible temperature.
Thermal Expansion of Solids, Liquids, and Gases
All materials generally expand on heating. Linear expansion (α) applies to rods and wires; area expansion (β = 2α) to plates; volume expansion (γ = 3α) to blocks and liquids. Water shows anomalous expansion — it contracts on heating from 0°C to 4°C — making ice float and aquatic life survive in cold winters.
Specific Heat Capacity and Calorimetry
Specific heat capacity (c) is the heat needed to raise 1 kg of a substance by 1 K. Water has an unusually high specific heat (~4186 J/kg·K), making it an excellent coolant. The Principle of Calorimetry — that heat lost by the hotter body equals heat gained by the cooler body — is used extensively in mixture problems.
Latent Heat and Change of State
During a phase change (melting, boiling), temperature remains constant even as heat is supplied. This heat is called latent heat. Latent heat of fusion of water is 334 J/g; latent heat of vaporisation is 2260 J/g — explaining why steam causes more severe burns than boiling water at the same temperature.
Heat Transfer: Conduction, Convection, Radiation
Conduction transfers heat through molecular vibrations in solids without bulk movement. Convection occurs in fluids via bulk movement (sea breezes, room heaters). Radiation needs no medium — it's energy transfer via electromagnetic waves. Stefan-Boltzmann and Wien's laws describe radiation quantitatively.
| Resource Name | Description | Best For |
|---|---|---|
| NCERT Solutions | Detailed answers and explanations for NCERT textbook questions across all classes and subjects. | Homework, assignments, and exam preparation |
| NCERT Solutions for Class 11 | Chapter-wise solutions for all Class 11 subjects including Physics, Chemistry, Mathematics, Biology, and English. | Class 11 board exam preparation |
| NCERT Solutions for Class 11 Physics | Step-by-step solutions covering all chapters such as Motion, Laws of Motion, Work Energy and Power, Thermodynamics, and Waves. | Concept building and numerical problem-solving |
| NCERT Exemplar Class 11 Physics | Advanced and application-based questions designed to strengthen conceptual understanding and analytical skills. | JEE, NEET, Olympiads, and higher-order practice |
| Physics Formula | Chapter-wise collection of important formulas, equations, and derivations for quick revision. | Last-minute revision and numerical practice |
Quick Reference Table – Important Constants and Values
| Quantity | Value | Remark |
|---|---|---|
| Specific heat of water | 4186 J/kg·K | Highest among common liquids |
| Specific heat of ice | 2090 J/kg·K | Half that of water |
| Latent heat of fusion (water) | 3.34 × 10⁵ J/kg | Energy for ice → water at 0°C |
| Latent heat of vaporisation (water) | 2.26 × 10⁶ J/kg | Energy for water → steam at 100°C |
| Thermal conductivity of copper | 385 W/m·K | Excellent conductor |
| Thermal conductivity of glass | ~0.8 W/m·K | Poor conductor (insulator) |
| Stefan-Boltzmann constant σ | 5.67 × 10⁻⁸ W/m²K⁴ | For blackbody radiation |
| Linear expansion of steel | α ≈ 1.2 × 10⁻⁵ K⁻¹ | Used in railway expansion gaps |