Points to Remember

Thermal Physics (Science)

Points to Remember

·                 The SI unit of heat energy absorbed or evolved is joule (J)

·                 Heat always flows from a system at higher temperature to a system at lower temperature.

·                 Temperature is defined as the degree of hotness of a body. The SI unit of temperature is kelvin (K).

·                 All the substances will undergo one or more of the following changes when heated:

i) Temperature of the substance rises.

ii) The substance may change state from solid to liquid or gas.

iii) The substance will expand when heated.

·                 All forms of matter (solid, liquid and gas) undergo expansion on heating.

·                 For a given rise in temperature, a liquid will have more expansion than a solid and a gaseous substance has the highest expansion than the other two.

·                 If a liquid is heated directly without using any container, then the expansion that you observe is termed as real expansion of the liquid.

·                 The expansion of a liquid apparently observed without considering the expansion of the container is called the apparent expansion of liquid.

·                 For a given heat energy, the real expansion is always more than that of apparent expansion.

·                 If the atoms or molecules of a gas do not interact with each other, then the gas is said to be an ideal gas or a perfect gas.

·                  Ideal gas equation, also called as equation of state is PV = RT. Here, R is known as universal gas constant whose value is 8.31 J mol−1K−1