What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

Distinguish heat from temperature.

Temperature measures the degree of hotness of a body; heat is the energy that flows between bodies because of a temperature difference.

Relate the Celsius and absolute temperature scales.

\(T(\text{K})=t_C+273.15\); absolute zero corresponds to \(-273.15^{\circ}\)C.

Relate the coefficients of linear and volume expansion.

For an isotropic solid \(\alpha_V\approx3\alpha_L\).

What is the anomalous expansion of water?

Between 0 and 4 degrees Celsius water contracts on heating and is densest at 4 degrees, which is why lakes freeze from the top.

State the principle of calorimetry.

When bodies at different temperatures are mixed in an isolated system, heat lost by the hot bodies equals heat gained by the cold bodies.

Define latent heat of fusion and of vaporisation.

Heat of fusion is the heat per unit mass to convert solid to liquid; heat of vaporisation is that to convert liquid to vapour, both at constant temperature.

Write the equation for heat conduction.

\(H=\dfrac{KA\,\Delta T}{L}\), where \(K\) is thermal conductivity, \(A\) the area, \(L\) the length and \(\Delta T\) the temperature difference.

Name the three modes of heat transfer.

Conduction (through matter without bulk movement), convection (bulk movement of fluid) and radiation (electromagnetic waves, needing no medium).

State Stefan's law and Wien's displacement law.

Stefan's law: radiated power per unit area is proportional to \(T^{4}\); Wien's law: the wavelength of maximum emission is inversely proportional to temperature.

State Newton's law of cooling.

The rate of loss of heat of a body is proportional to the difference between its temperature and that of its surroundings, for small differences.

Thermal Properties of Matter

Class 11 Physics · Physics Part II · Chapter 3

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CBSE Class 11 · Physics

Ch 8–14 formulas and table values, by page

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Summary

Temperature is a measure of the hotness of a body, and heat is energy transferred between a body and its surroundings because of a temperature difference. Temperature is measured on the Celsius, Fahrenheit and absolute (Kelvin) scales, related by \(t_F=\tfrac95 t_C+32\) and \(T=t_C+273.15\); the ideal-gas equation \(PV=\mu RT\) defines absolute temperature, with absolute zero at \(-273.15^{\circ}\)C. Most substances expand on heating, characterised by coefficients of linear, area and volume expansion with \(\alpha_V\approx3\alpha_L\); water shows anomalous expansion near 4 degrees Celsius. Specific heat capacity is the heat needed to raise unit mass by one degree, and molar specific heat refers to one mole; calorimetry uses the principle that heat lost equals heat gained. During a change of state — melting, vaporisation — temperature stays constant and the heat absorbed is the latent heat. Heat is transferred by conduction (through \(H=KA\,\Delta T/L\)), convection and radiation. A black body absorbs all radiation; Stefan's law gives the radiated power as proportional to \(T^{4}\), Wien's law gives the wavelength of peak emission, and the greenhouse effect warms the Earth. Newton's law of cooling states that the rate of cooling is proportional to the temperature difference with the surroundings.

Temperature and heat; measurement of temperatureIdeal-gas equation and absolute temperatureThermal expansionSpecific heat capacity and calorimetryChange of state and latent heatHeat transfer: conduction, convection, radiationNewton's law of cooling

Key terms

Heat

Energy transferred between a system and its surroundings owing to a difference of temperature.

Absolute temperature

Temperature measured on the Kelvin scale, defined through the ideal-gas equation with zero at \(-273.15^{\circ}\)C.

Coefficient of linear expansion

The fractional increase in length per unit rise in temperature, \(\alpha_L=\Delta L/(L\,\Delta T)\).

Specific heat capacity

The heat required to raise the temperature of unit mass of a substance by one degree.

Latent heat

The heat absorbed or released per unit mass during a change of state at constant temperature.

Thermal conductivity

A measure of a material's ability to conduct heat, the constant \(K\) in \(H=KA\,\Delta T/L\).

Extra questions & answers

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Heat is energy that flows because of a difference in:

Flashcards & interactive practice