The thermal state or condition of a body which determines whether a body can gives out heat to or receive heat from another body placed in contact with it, is known as it’s temperature.
Heat flows of itself from a body at a higher temperature to another at a lower temperature. Temperature may be termed as the degree of hotness or coldness. For the measurement of temperature of a body or a system some physically measurable properties of the working substance must be used. The instrument depending on these properties and measure the temperature accurately, is known as thermometer.
Unit of temperature: In SI system the unit of temperature is Kelvin (K).
Kelvin: The particular temperature and pressure at which water remains at its three states- solid, liquid and gas, is called the triple point of water. The temperature of the triple point of water is considered as
273 K. 1/ 273.16 th part of the temperature of the triple point of water is called 1K.