“The mode of transfer of heat by vibrating atoms and free electrons in solids from hot to cold parts of a body is called conduction of heat.”
The handle of metal spoon held in hot water soon gets warm.But in case of a wooden spoon,the handle does not get warm.Both the materials behave differently regarding the transfer of heat.Both metals and non metals conduct heat.Metals are generally better conductors than non metals.
Heat conduction in solids
In solids,atoms and molecules are packed close together.They continue to vibrate about their mean position.What happens when one of its ends is heated?The atoms or molecules present at that end begin to vibrate more rapidly.They also collide with their neighbouring atoms or molecules.In doing so,they pass some of their energy to neighbouring atoms or molecules during collisions with them will increase in their vibrations.These atoms or molecules in tern pass on a part of the energy to their neighbouring particles.In this way some heat reaches the other parts of the solids.This is a slow process and very small transfer of heat takes place from hot to cold parts in solids.
How do metals differ from non-metals in terms of conducting heat?
Metals have free electrons.These free electrons move with very high velocities within the metal objects.They carry energy at a very fast rate from hot to cold parts of the object as they move.Thus ,heat reaches the cold parts of the metals objects from its hard parts much more quickly than non metals.
All metals are good conductors of heat.The substances through which heat does not conduct easily are called bad conductors or insulators. Wood,cork,cotton,wool,glass,rubber,etc are bad conductors or insulators.
Applications of conduction of heat in our daily life
Use of good conductors of heat
- Cooking utensils,saucepans,kettles and boilers are made of metals where direct heating is involved.
- Soldering iron are made of tron with tip made of copper because copper is much better conductor of heat than iron.
Use of insulators or bad conductors
Some common applications of insulators are given:
- Handles of kettles and spoons are made of plastic or wood because wood is poor conductor of heat.In this way the hot kettles,utensils and spoons can be picked up without burning our hands.
- Woolen clothes or blankets are used to keep people warm on cold days.
- Sawdust is used to cover up ice blocks because it has good insulating property.