SCIENCE : Transfer of heat

TRANSFER OF HEAT

Heat is a quality of being  hot or a having a high temperature in it.Let us explore how Heat is being transferred from one object to other object.

Now let us start with a question,

  Your mother has kept the dosa pan in the stove under flame and she has forgotten to as such without preparing dosa.After sometime you get a bad smell and run over there for the dosa pan.You cannot touch the pan as such since it will be too hot.You use a cloth to take out and keep it separate.At first the pan was too hot and after sometime it becomes cold.But how it become cold?Where the hotness gone from the pan?Is it a magic ?

So,the science behind this is Transfer of heat !

There are some ways by which heat get transferred which we will deal below.

Heat can be transferred from one place to another by three methods:                  

Conduction in solids.

Convection of fluids (liquids or gases). 

Radiation through anything that will allow radiation to pass. 

The method used to transfer heat is usually the one that is the most efficient. If there is a temperature difference in a system, heat will always move from higher to lower temperatures.

CONDUCTION

•  Conduction occurs when two object at different temperatures are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature. 
•  Conduction is the movement of heat through a substance by the collision of molecules. 
• At the place where the two object touch, the faster-moving molecules of the warmer object collide with the slower moving molecules of the cooler object.
•  As they collide, the faster molecules give up some of their energy to the slower molecules. The slower molecules gain more thermal energy and collide with other molecules in the cooler object. 
• This process continues until heat energy from the warmer object spreads throughout the cooler object. 
• Some substances conduct heat more easily than others. 
• Solids are better conductor than liquids and liquids are better conductor than gases. Metals are very good conductors of heat, while air is very poor conductor of heat. 
• You experience heat transfer by conduction whenever you touch something that is hotter or colder than your skin.

 e.g. When you wash your hands in warm or cold water. 



CONVECTION 

•  In liquids and gases, convection is usually the most efficient way to transfer heat.
•  Convection occurs when warmer areas of a liquid or gas rise to cooler areas in the liquid or gas. 
• As this happens, cooler liquid or gas takes the place of the warmer areas which have risen higher. This cycle results in a continuous circulation pattern and heat is transferred to cooler areas. 
• You see convection when you boil water in a pan. The bubbles of water that rise are the hotter parts of the water rising to the cooler area of water at the top of the pan. 
• You have probably heard the expression "Hot air rises and cool air falls to take its place" - this is a description of convection in our atmosphere. Heat energy is transferred by the circulation of the air.

RADIATION 

• Both conduction and convection require matter to transfer heat. Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object. 
• For example, we feel heat from the sun even though we are not touching it. 
• Heat can be transmitted though empty space by thermal radiation. 
• Radiation is a form of energy transport. No medium is required. 

So, In this blog you have learnt about the heat,Transfer of heat and also the types of transfer of heat. Up to now whatever you have learnt is just a superficial content.The deepness of the content stated above will  be continued in the following blogs.

Thank you !

References: NCERT textbooks.