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# CBSE CLASS 7-Heat

## HEAT

·         Heat is a  the energy stored inside an object.

·         Degree of hotness/cold of an object is its temperature.

·         Heat always flows from hot to cold objects.

·         When a hot and a cold body are kept in thermal contact, they exchange heat until they acquire thermal equilibrium (both the object acquire the same temperature), with the cold body warming up & the hot body cooling down.

MEASURING TEMPERATURE

·         Temperature is measured by using a device known as thermometer.

## Clinical thermometer

·         The thermometer that are used to measures our body temperature is called a clinical thermometer.

·         A clinical thermometer consists of a  narrow, long, uniform glass tube. It has a bulb at one end. This bulb contains mercury.  A small shining thread of mercury can be seen outside of the thermometer.

·         The scale we use generally is Celsius scale, indicated by °C.

·         Human body's normal temperature of  the  is 37°C.

·         The clinical thermometer is  used to measure the temperature of human body only.

·         The temperature of the human body normally between 35 °C or above 42°C.

·         Range of clinical thermometer:35°C to 42°C.

LABORATORY THERMOMETER

·         The range of a laboratory thermometer is generally from –10°C to 110°C hence used in laboratory.

## Heat transfer

·         Heat can transferred through three means: conduction, convection and radiation.

·         Conduction: The method of transfer of heat in solids is called Conduction.

·         Conduction is the transfer of heat transfer in material from one molecule to another. Generally the more energetic to less energetic particles of a substance due to interaction between the particles.

·         Convection is the process of heat transfer by the movement of a molecule a fluid (liquid & gas-that can flow).

T  The mode of heat transfer from one object to another without heating in the intermediate medium is called convection.

·        Radiation is energy that comes from a source and travels in space at the speed of light.

## Conductor & Insulator

·         The materials that allow heat to pass through them are called conductors.

·       The materials that  do not allow heat to pass through them are called insulator.

## Sea breeze & land breeze

·         Land breeze and sea breeze are observed near large bodies of water.

·         The flow of the wind from land to sea is known as the land breeze.

·         Land breeze occurs during the night time. This is because during the night time, land gets cooled faster than the sea and the warm air above the sea rises up and  the cold air from the land flows towards the sea causing land breeze.

·         The flow of the wind from sea to land is known as the sea breeze.

·         Sea breeze occurs during the daytime. This is because during the daytime, land gets heated up faster than the sea and the warm air above the land rises up. Thus the cold air from the sea flows towards the land resulting sea breeze.