If there is an increase in the volume of a solid object due to heating, then the expansion is called cubical or volumetric expansion.

Increase in area per unit original area, per degree celsius rise in temperature is called coefficient of superficial expansion.
\(\frac { \triangle L }{ { A }_{ 0 } } ={ \alpha }_{ A }\triangle T\Rightarrow \alpha _{ A }\frac { \triangle A }{ \triangle T.A_{ 0 } } \)
ΔL = change in Area
A_{0 =} original Area
ΔT =change in Temperature
α_A = coefficient of superficial expansion

(i) Increase in length per unit of the length of the solid object per degree celsius rise in temperature is called 'coefficient of linear expansion'.
(ii) Its SI unit is per kelvin.
\(\frac { \triangle L }{ { L }_{ 0 } } ={ \alpha }_{ L }\triangle T\Rightarrow { \alpha }_{ L }\frac { \triangle L }{ \triangle T.L_{ 0 } } \)
ΔL - change in length
L₀ - original length
ΔT - change in Temperature
α_L - coefficient of Linear expansion

When an object is heated or cooled, if the length of the object changes due to change in the temperature then the expansion is said to be linear or longitudinal expansion.

When heat energy is supplied to an object, there can be an increase in the dimension of the system. This change in the dimension due to rise in temperature is called thermal expansion of the object.

(i) Temperature of the substance rises.
(ii) The substance may change its state from solid to liquid or liquid to gas.
(iii) The substance will expand when heated.

One kilocalorie is the amount of heat required to rise the temperature of 1 kilogram of water through 1°C.

One joule is defined as the work done when a force of 1N is applied on an object to produce a displacement of one metre.

(i) Heat always flows from a system at higher temperature to a system at lower temperature.
(ii) The mass of a system is not altered when it is heated or cooled.
(iii) For any exchange of heat, the heat gained by the cold system is equal to heat lost by the hotter system.

This process of transmission may be done in any of the ways like conduction, convection or radiation.

The process in which heat energy flows from a object at a higher temperature to another object at lower temperature is known as heating.

Thermal energy is a form of energy which is transferred between any two objects due to the difference in their temperatures.

It is defined as the fraction, 1/273.16 of the thermodynamic temperature of triple point of water.

The temperature measured in relation to absolute zero using the Kelvin scale is known as absolute temperature.

Temperature is defined as the degree of hotness of a body. It is also defined as the property which determines whether a body is in equilibrium or not with the surroundings.