CBSE Class 11 Physics Chapter 10 Notes: Thermal Properties of Matter

Thermal Properties of Matter is the study of how heat energy affects the physical state, dimensions, and temperature of substances, and how heat flows between bodies through conduction, convection, and radiation. These class 11 physics chapter 10 thermal properties of matter notes follow the NCERT Physics Part II Reprint 2026-27 sequence exactly.

Cbse Class 11 Physics Chapter 10 Notes covers temperature measurement, thermal expansion, specific heat, calorimetry, change of state, and all three heat transfer modes. Students who understand this chapter as a flow, from defining temperature to explaining why a cup of tea cools, answer both concept and numerical questions cleanly. These thermal properties of matter class 11 notes are high-yield for CBSE 2026 boards and essential for JEE and NEET preparation. Use them alongside Important Questions Class 11 Physics Chapter 10 for exam practice. 

Key Takeaways: CBSE Class 11 Physics Chapter 10

Temperature and Heat

Temperature and heat are two of the most confused terms in physics. Understanding the difference between them is the starting point for all thermal properties of matter class 11 notes.

Temperature is a relative measure of the hotness or coldness of a body. Hot and cold are relative terms like tall and short. Our temperature sense is unreliable, so thermometers are used for scientific measurement. The SI unit of temperature is Kelvin (K).

Heat is the form of energy transferred between two systems by virtue of a temperature difference. Heat always flows from higher to lower temperature until thermal equilibrium is reached. The SI unit of heat is joule (J).

Measurement of Temperature

A thermometer uses a thermometric property, a physical property that changes reliably with temperature to assign a numerical value. The most common property is the variation of liquid volume with temperature, used in mercury and alcohol thermometers.

Two fixed reference points define any standard scale. The ice point is the freezing point of water at standard pressure. The steam point is the boiling point of water at standard pressure.

Celsius scale: Ice point = 0°C, steam point = 100°C Fahrenheit scale: Ice point = 32°F, steam point = 212°F

Conversion between scales: (tF - 32) / 180 = tC / 100 or: tF = (9/5)tC + 32

Ideal-Gas Equation and Absolute Temperature

Liquid-in-glass thermometers give different readings for different liquids because of differing expansion properties. A constant-volume gas thermometer gives the same readings regardless of which gas is used at low density.

The variables describing a gas — pressure (P), volume (V), and absolute temperature (T) — follow the ideal gas equation: PV = muRT where mu is the number of moles and R = 8.31 J mol-1 K-1 is the universal gas constant.

When a pressure-temperature graph for any low-density gas is extrapolated, it meets the temperature axis at -273.15°C. This is absolute zero — the foundation of the Kelvin scale. T = tC + 273.15

The triple point of water is assigned 273.16 K. It is the standard fixed point in modern thermometry because it has one unique, reproducible temperature.

Thermal Expansion

Most substances expand on heating and contract on cooling. This increase in dimensions due to a rise in temperature is called thermal expansion. The three types of expansion — linear, area, and volume — are tested regularly in class 11 thermal properties of matter notes questions.

Linear expansion: Delta-l / l = alphal x DeltaT Area expansion: Delta-A / A = 2alphal x DeltaT Volume expansion: Delta-V / V = alphaV x DeltaT Relation between coefficients: alphaV = 3alphal

Metals have higher alphal than non-metals. Copper expands about five times more than glass for the same temperature rise.

Thermal Stress

When a rod cannot expand freely because its ends are fixed, it develops compressive strain. The stress that results is called thermal stress.

Thermal stress = Y x alphal x DeltaT

where Y is the Young's modulus of the material. This matters for railway tracks, bridges, and metal structures. Gaps are left between railway tracks precisely to allow for thermal expansion.

Anomalous Expansion of Water

Water contracts on heating between 0°C and 4°C, which means its density increases in this range. Water reaches maximum density at 4°C. Below 4°C, volume increases and density decreases again.

This is why lakes and ponds freeze at the top first. Surface water below 4°C becomes less dense and stays at the top, where it freezes. The water below remains liquid, protecting aquatic life through winter.

Specific Heat Capacity

Specific heat capacity is the amount of heat per unit mass required to raise the temperature of a substance by one unit. Two substances of the same mass absorb different amounts of heat for the same temperature rise.

s = (1/m) x (DeltaQ / DeltaT) SI unit: J kg-1 K-1

Molar specific heat capacity is the heat required to raise the temperature of one mole of a substance by one unit. C = (1/mu) x (DeltaQ / DeltaT) SI unit: J mol-1 K-1

Water has the highest specific heat capacity among common substances at 4186 J kg-1 K-1. This is why water is used in automobile radiators and hot water bags. It also explains why coastal regions have milder climates than inland areas.

Calorimetry

Calorimetry is the science of measuring heat exchange between bodies. The principle rests on one rule: in an isolated system, heat lost by the hot body equals heat gained by the cold body.

A calorimeter is a metallic vessel kept inside a wooden jacket with insulating material (glass wool) to minimise heat loss to surroundings. This ensures accurate measurement.

For temperature change: Q = ms x DeltaT For molar heat: Q = nC x DeltaT

Change of State

Matter exists in three states: solid, liquid, and gas. A transition between states is called a change of state. All heat supplied during a phase change goes into changing the state, not raising the temperature — the temperature stays constant throughout.

Melting point: Temperature at which solid and liquid coexist in thermal equilibrium. Boiling point: Temperature at which liquid and vapour coexist.

Boiling point increases with pressure — this is the pressure cooker principle. Boiling point decreases at higher altitudes where atmospheric pressure is lower, which is why cooking takes longer in hill stations.

Regelation is the refreezing of water that melted due to increased pressure. This is why a weighted wire can pass through an ice slab. Sublimation is the direct transition from solid to vapour. Examples: dry ice (solid CO2) and iodine.

Latent Heat

Latent heat is the amount of heat per unit mass transferred during a change of state, with no change in temperature.

Q = mL SI unit: J kg-1

Latent heat of fusion (Lf): Heat required to convert solid to liquid. Latent heat of vaporisation (Lv): Heat required to convert liquid to vapour.

For water: Lf = 3.33 x 10^5 J kg-1 Lv = 22.6 x 10^5 J kg-1

Steam at 100°C carries 22.6 x 10^5 J kg-1 more heat than water at 100°C. When steam condenses on skin, it releases this latent heat in addition to the heat from cooling. Burns from steam are more serious than burns from boiling water for exactly this reason.

Triple Point and Phase Diagram

A phase diagram (P-T diagram) shows regions where each state of matter is stable. The sublimation curve, fusion curve, and vaporisation curve all meet at one point: the triple point.

The triple point is the temperature and pressure at which all three phases coexist simultaneously. For water: 273.16 K and 6.11 x 10-3 Pa. The triple point of water is the standard fixed point in modern thermometry because it occurs at one specific, reproducible temperature regardless of external conditions.

Heat Transfer

Heat moves from one body to another through three distinct mechanisms. Every thermal properties of matter class 11 important questions set includes at least one question comparing these three modes.

Each mode operates under different physical conditions. Conduction works in solids, convection works in fluids, and radiation works even in vacuum.

Conduction

Conduction is the transfer of heat between adjacent parts of a body through molecular collisions, without any flow of matter.

For a bar of length L, cross-sectional area A, with ends at temperatures TC and TD: H = KA(TC - TD) / L

where K is thermal conductivity (SI unit: W m-1 K-1). Higher K means faster heat transfer for a given temperature difference.

Thermal resistance of a conductor: Rth = L / KA Temperature gradient: Decrease in temperature per unit length in the direction of heat flow.

Convection

Convection is the transfer of heat by the actual movement of heated matter. It operates only in fluids — liquids and gases.

Natural convection occurs due to density differences caused by temperature. Hot fluid expands, becomes less dense, rises, and cooler fluid replaces it. Examples: sea breezes, land breezes, trade winds.

Forced convection occurs when fluid is moved by a pump or fan. Examples: automobile cooling systems, the human circulatory system, forced-air heating.

Radiation

Radiation is the transfer of heat through electromagnetic waves. No medium is required — heat from the Sun reaches Earth across the vacuum of space. All bodies emit radiant energy by virtue of their temperature.

Black surfaces absorb and emit radiant energy more effectively than lighter surfaces. This is why dark-coloured clothes keep you warmer in winter and light-coloured clothes keep you cooler in summer.

Blackbody Radiation, Wien's Displacement Law, and Stefan-Boltzmann Law

A blackbody emits thermal radiation across a continuous spectrum of wavelengths. Two laws govern this emission and both appear frequently in thermal properties of matter class 11 questions and answers.

Wien's Displacement Law states that the wavelength at which energy emission is maximum shifts with temperature: lambdaM x T = 2.9 x 10-3 m K

As temperature increases, peak wavelength decreases. This explains why heated iron glows dull red first, then yellow, then white hot. Solar radiation peaks at lambdaM = 4753 angstroms, giving the Sun's surface temperature as approximately 6060 K.

The Stefan-Boltzmann law gives the energy emitted per unit time by a perfect blackbody: H = A x sigma x T^4

For a real body with emissivity e: H = Ae x sigma x T^4

where sigma = 5.67 x 10-8 W m-2 K-4 is the Stefan-Boltzmann constant.

For a body at temperature T with surroundings at temperature Ts, the net rate of heat loss is: H = e x sigma x A(T^4 - Ts^4)

Newton's Law of Cooling

Newton's law of cooling connects directly to radiation and is a common source of numerical questions in CBSE 2026 exams. It applies when the temperature difference between a body and its surroundings is small.

The rate of loss of heat from a body is directly proportional to the temperature difference between the body and its surroundings.

-dQ/dt = k(T2 - T1)

where k is a positive constant depending on the area and nature of the surface, T2 is body temperature, and T1 is surrounding temperature.

For a body of mass m and specific heat s: dT2 / (T2 - T1) = -K dt

On integrating: loge(T2 - T1) = -Kt + c or: T2 = T1 + C'e^(-Kt)

Approximation formula for small temperature differences: Change in temperature / Time = K x DeltaT

This equation calculates the time a body takes to cool through a given temperature range — a direct exam application.

Thermal Properties of Matter Important Formulas

Thermal Properties of Matter Short Notes

These thermal properties of matter short notes cover every must-know point for last-minute revision before CBSE 2026 exams.

These thermal properties of matter class 11 short notes work best when used alongside full section revision, not as a substitute for it.

Thermal Properties of Matter Class 11 Important Questions and Answers

These thermal properties of matter class 11 important questions come from NCERT exercises and standard CBSE exam patterns. Working through them builds the answer-writing speed needed for 2026 exams. For a complete set, visit Important Questions Class 11 Physics Chapter 10.

Q1. Why are burns from steam more serious than burns from boiling water at the same temperature? Steam at 100°C carries 22.6 x 10^5 J kg-1 more heat than water at 100°C due to its latent heat of vaporisation. When steam condenses on skin, it releases this additional latent heat along with the heat from cooling. This makes burns from steam far more severe than burns from boiling water.

Q2. Why does water freeze at the top of a lake first? Water has maximum density at 4°C. As a lake cools, denser water sinks and warmer water rises. Once surface water cools below 4°C, it becomes less dense and stays at the top, where it freezes. This is the anomalous expansion of water in action.

Q3. A bimetallic strip bends on heating. Why? A bimetallic strip joins two metals with different coefficients of linear expansion. On heating, one metal expands more than the other. The metal with the higher coefficient forms the outer convex side of the arc. The metal with the lower coefficient forms the inner concave side.

Q4. Why is cooking difficult at high altitudes? At high altitudes, atmospheric pressure is lower. Lower pressure reduces the boiling point of water below 100°C. Food takes longer to cook because water boils at a lower temperature. A pressure cooker raises the boiling point by increasing pressure inside.

Q5. Why do we wear dark-coloured clothes in winter? Dark surfaces absorb and emit radiant energy more effectively than lighter surfaces. Dark-coloured clothes absorb more heat from solar radiation and from the body, keeping the wearer warmer in winter.