Class 7 | Science | Chapter-4 | Heat Notes

Class 7           Science

Chapter-4

Heat Notes

Heat- It is a form of energy. Which makes any object hot and cold.

Temperature- Temperature is a measure of the degree of hotness of an object.

Our sense of touch is not always a reliable guide to the degree of hotness of an object.

The normal temperature of human body is 37℃ and slightly higher or slightly lower.

Thermometer- Thermometer is device used for measuring temperature.

Thermometer is classified in two categories

Clinical Thermometer- This thermometer is measure our body temperature is called clinical thermometer. Its range is 35℃ to 42℃. A clinical thermometer consist of a long, narrow, uniform glass tube. It has a bulb at one end. This bulb contain mercury, and near the bulb kink is present. Kink prevents mercury level from falling on its own.

Clinical Thermometer

Laboratory Thermometer- It is used in measuring water and chemicals temperature. its range is -10℃ to 110℃. In laboratory thermometer kink is absent.

                 Laboratory Thermometer

Transfer of Heat-

The heat flows from a body at a higher temperature to a body at a lower temperature.  There are three ways in which heat can flow from one object to another. These are  conduction, convection and radiation.

Conduction-  The process by which heat is transferred from the hotter end to the colder end of an object is known As conduction.

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

Radiation- It is the mode of transfer of heat in which energy is directly transferred from one place to another.  It is not required any medium.

Conductors- The materials which allow heat to pass through them easily are called conductor.

Insulators- The materials which do not allow heat to pass through them easily are called insulators.

Sea Breeze- The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called sea breeze. The Sea breeze form at During Day.

Land Breeze- The cool air from the land
moves towards the sea. This is called the land breeze. It is form at night.

Dark- coloured objects absorb more heat than the light coloured objects. That is the reason we feel more comfortable in light coloured clothes in the summer.

Wollen clothes keep us warm during winter. It is so because wool is a poor conductor of heat and it has air trapped in between the fibres.