# Heat

Heat is reffered as transfer of energy from hot object to cool object. When heat is given to any object its temprature rises, so the temprature is the degree of hotness of a substance. Temprature is measured in the unit of degree Celsius or Kelvin(k). The Kelvin Temprature Scale is also called as Absolute Temprature Scale.

## Celsius Scale of Temprature

On Celsius scale of temperature 0° represents the melting point of ice and 100° represents the boiling point of water.

## Kelvin Scale of Temprature

A scale of temperature beginning at absolute zero (-273.15°C). Each degree, or kelvin, has the same value as one degree on the Celsius scale. On the Kelvin scale water freezes at 273.15 K and boils at 373.15 K.
Temprature on kelvin scale = Temprature on Celsius scale + 273,
K = C + 273

## Measurement of Temperature

The temperature of a body is measured by an instrument called thermometer. Their are two types of thermometer which are commonly used:

1. Labortory Thermometer : It is a mercury thermometer. A common laboratory thermometer can measure tempratures from -10° C to 110° C.
2. Clinical Thermometer : It is used to measure the temprature of human body, it have a very small range of temprature from 35° C to 42° C, this is because the temprature of human body never goes beyond these temprature

## Thermal Equilibrium

When two bodies are in contact with each but no heat flows from one body to the other this condition is known as thermal equilibrium

## Units of Heat

The SI unit of heat is Jule how ever heat is also measured in calorie, 1calorie = 4.18 joules

## Specific Heat

The amount of heat which is used to raise the temprature of unit mass by one degree celcius is known as specific heat and its SI unit is 'joule/kg/degree celcius'

## Thermal Expension

The expansion of a body due to increase in temprature is called as thermal expension. Their are many type of expension in body. Like linear expansion, circular expansion, cubical expension etc.

## Latent Heat

When heat is supplied to change the state of a substance and there is no rise in temperature of the substance. The SI unit of latent heat is Jule.

1. Latent Heat of Fusion: The latent heat of fusion of a substance is the amount of heat required to convert a unit mass of the substance from the solid state to the liquid state without change of temprature
2. Latent Heat of Vaporization: The heat required to convert a liquid into the vapour state is called latent heat of vaporization. The latent heat of vaporization of a substance is the amount of heat required to change a unit mass of the substance from the liquid state to vapour state without change of temprature

## Evaporation

The process of changing liquid into vapour even below its boiling point is called as evaporation.

## Humidity

The presence f water vapour in the air is known as its humidity. The air containing maximum possible amount of water vapour in it, is said to be saturated.