Conduction
The molecules in the solids are tightly packed.
When heated at one end, the molecule absorbs heat and it vibrates in its position, and the molecule at the other gets heated.
These heated molecules, in turn, heat other molecules, till everything gets heated.
“The process of heat transfer in solids from an area of higher temperature to an area of lower temperature without the actual displacement of the molecule is called Conduction”
Conduction in Daily Life
Good conductors of heat
Metal is a good conductor of heat and as a result cooking utensils are made of metals.
Mercury, which liquid metal is a good conductor of heat. That’s why it is used in thermometers.
Poor conductors of heat
We wear woolen clothes during winter to stay warm from the cold. Because woolen has a lot of air locked inside, as the air is a bad conductor, it does not allow heat from the body to escape outside. Thereby it keeps us warm.
Snow is used to building Igloo as snow is a poor conductor, it keeps people inside warm. Also, animal skins are used as door flaps to allow warm air inside.
Ice beds are made inside the igloo which is made of Ice and Caribou furs.
Convection
When the air is heated the air molecules gain heat energy allowing them to move further apart. Warm air is light, less dense than cold air, and will rise.
Cooler air heavy than the warm air, and go down. Cooler then gets heated and rises above.
Similarly, warm air gets cooled and goes down. This process creates a circular flow.
“Convection is the flow of heat via a fluid from places of higher temperature to a place of lower temperature by the movement of the fluid itself”.
Convention in Daily Life
Hot Air Balloon
In Hot Air Balloon, Air is heated. The heated air is allowed to fill the balloon. As hot air is less dense, the Hot air balloon rises high.
Breezes
During daytime air in the land gets heated and rises above. Now cool air from the sea replaces the space previously occupied by the hot air.
It is called Sea breeze. During the nighttime, the land gets cooler fast and cools the air. Sea does not cool faster, as result air above the sea is warmer. The warmer air rises high.
The cold air from the land replaces the space above the sea. This is called Land Breeze.
Winds
Air flows from the area of high pressure to the area of low pressure. The warmer air rises create a low pressure.
The cooler air with high pressure flows toward the low-pressure area. This is how Winds are formed.
Chimneys
Chimneys are kept in industrial furnaces, kitchens, etc as hot gases and smoke are lighter and rise to the atmosphere.
Radiation
Radiation is a method of heat transfer without the involvement of particles. Radiation employs waves to transfer heat.
The waves are transferred in all directions. Radiation can transfer heat even in a vacuum, where conduction and convection cannot take place.
Radiation comprises electromagnetic waves that travel at light speed (3 x 106 m/s). Thus radiation is transferred heat by electromagnetic waves.
The heat from the sun reaches the earth in the form of radiation. Radiation is emitted by all the bodies above 0 K. Some things reflect radiation and some absorb radiation.
Radiation in Daily Life
White or light-colored clothes are good reflectors of heat and feel cool during summer. The base of cooking utensils is blackened because it absorbs more heat.
The surface of the Airplane is polished to reflect radiation from the Sun.