CLASS - 7 SUB-SCIENCE CHAPTER-4 HEAT

Hot:- The object is said to be hot if having a high degree of heat or a high temperature.

Cold:- The object is said to be cold if having a low degree of heat or a low temperature.

Temperature:-  A reliable measure of the hotness of an object is its temperature .Temperature is measured by a device called thermometer.

There are two type of Thermometer:-

1.Clinical Thermometer

2.Laboratory Thermometer

        

                                      Differnce between

⦁ The Maximum-Minimum thermometer is used to measure the  temperature of weather.

⦁ The temperature of human body is 37 degree celcius or  slightly higher or  slightly                 lower.

Conductors:- The materials which allow heat to pass through them easily are conductors ofheat. For examples, aluminum, iron and copper.

Insulators:- The materials which do not allow heat to pass through them easily are poor conductors of heat such as plastic and wood. Poor conductors are known as insulators. The water and air are poor conductors of heat. 

Transfer of Heat:- Heat transfer from higher temperature to lower temperature.There are three way in which heat can  flow.

1.Conduction:-The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction conduction. In solids, generally, the heat is transferred by the process of conduction.

2.Convection:-It is the flow of heat through a fluid from place of higher temperature to place of lower temperature by movement of fluid itself.

3.Radiation:- It is mode of transfer of heat in which energy directly transfer from one place to another. It does not need any material medium.

Type of clothes in different season:-

In Summer season:- In summer season, we wear cotton and light coloured clothes. Light coloured clothes absorb less rediation than dark coloured clothes.

In Winter season:- In winter season season, we wear woollen and dark coloured clothes. Dark coloured clothes absorb more rediation than light coloured clothes and woollen clothes are bad conductor of heat, so the clothes contain the heat of body.

Sea Breeze:- The land gets heated up by the heat radiated by the sun, much faster than the water during daytime. This heats up the air over the land and it expands and hence the hot air rises up and creates a vacuum. The cool air from the sea occupies the space left by the hot air. The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called the sea breeze.

Land Breeze:-At night,The land cools down quickly and sea water remains hot. This heats up the air over the sea and it expands and hence the hot air rises up and creates a vacuum. The cool air from the land occupies the space left by the hot air. And hence the cool air moves from the land to the sea and is known as the land breeze.