THERMAL PROPERTIES OF MATTER
Frequently Asked Questions
Temperature is a measure of the degree of hotness or coldness of a body and determines the direction of heat flow.
Heat is a form of energy transferred from one body to another due to a temperature difference.
No
Thermal equilibrium is the state in which bodies in contact attain the same temperature and no net heat transfer occurs.
If two systems are each in thermal equilibrium with a third system
It forms the basis of temperature measurement and the construction of thermometers.
Thermal expansion is the increase in dimensions of a substance when its temperature rises.
Linear expansion
It is the fractional change in length per unit original length per unit rise in temperature.
Change in length is given by \( \Delta L = L_0 \alpha \Delta T \).
Areal expansion is the increase in surface area of a solid due to rise in temperature.
Volumetric expansion is the increase in volume of a substance with temperature.
For isotropic solids
To allow thermal expansion and prevent buckling during high temperatures.
Water contracts on heating from \(0^\circ\text{C}\) to \(4^\circ\text{C}\) and expands beyond \(4^\circ\text{C}\).
It enables aquatic life to survive in cold regions during winter.
Heat capacity is the amount of heat required to raise the temperature of a body by \(1\
Heat required to raise the temperature of unit mass of a substance by \(1\
The SI unit is \( \text{J kg}^{-1}\text{K}^{-1} \).
Heat required to raise the temperature of one mole of a substance by \(1\
\(C_p\) is molar heat capacity at constant pressure
At constant pressure
Calorimetry is the science of measuring heat exchanged in physical or chemical processes.
Heat lost by the hot body equals heat gained by the cold body
A calorimeter is a device used to measure heat transfer.
It is the mass of water that absorbs the same heat as the given body for the same temperature change.
Latent heat is the heat absorbed or released during a phase change without temperature change.
Heat required to convert unit mass of solid into liquid at its melting point.
Heat required to convert unit mass of liquid into vapor at its boiling point.
Supplied heat is used to overcome intermolecular forces
The rate of loss of heat is proportional to the temperature difference between the body and surroundings.
\( \frac{dT}{dt} \propto (T - T_s) \).
Small temperature difference
Conduction is heat transfer without bulk motion of particles.
Thermal conductivity measures a material’s ability to conduct heat.
The SI unit is \( \text{W m}^{-1}\text{K}^{-1} \).
Convection is heat transfer by actual movement of fluid particles.
Natural convection occurs due to density differences; forced convection uses external agents.
Radiation is heat transfer through electromagnetic waves without a medium.
A black body is an ideal body that absorbs all incident radiation.
Emissivity is the ratio of radiation emitted by a body to that emitted by a black body at the same temperature.
Black surfaces absorb more radiant heat
White reflects most radiation
Thermal stress develops when thermal expansion or contraction is restricted.
\( Q = mc\Delta T \) is the fundamental heat equation.
Heat during phase change is given by \( Q = mL \).
\( \Delta V = V_0 \gamma \Delta T \).
Metals conduct heat away from the body faster than wood.
Used in thermostats
Focus on formulas
