Conduction

It is the process of heat transfer in which the heat is passed on from particle to particle from the hot end of a body to its cold end without a bodily movement of matter.

Activity D

Note the temperatures at points T1, T2, and T3. Temperature at T1 increases first, then at T2 and then at T3. Thus, heat flows step by step from A to B.

Activity E

Take an iron rod and fix the pins on it using molten wax at different locations from end A. Heat end A by candle flame. It will be observed that the pin at 1 drops first, then successfully at points 2,3,4, and 5.

Theoretical Explanation

Molecules of a solid are very closely packed and hence cannot move about freely within the body. They only vibrate around their fixed positions. When one end of a rod is heated, the molecules at that end have more energy due to heat and begin to vibrate more rapidly. When these molecules collide with high neighboring molecules, some energy is passed on to them. Now these molecules in turn begin to vibrate faster and pass on same energy on to their neighboring molecules. Heat energy is thus transferred from molecule to molecule through the whole length of the rod, but the molecules themselves do not move along the rod, they only vibrate staying close to one position.