Heat Transfer Mechanisms 1.In your own words, using the pennies activity, define the three different heat transfer mechanisms. Your definitions should include: (i) information about how energy is moving
(ii) what is happening microscopically (that is, at the atomic level)
(iii) what phase(s) of materials is usually involved.

The three modes of heat transfer are: 1) Radiation 2) Convection 3) Conduction

Explanation:

RADIATION:

It is the mode of heat transfer which requires no medium because the transfer of energy takes place in the form of electromagnetic radiations. The spectrum of radiations that contribute to the heat transfer via radiation is the wavelength ranging from 0.1 μm to 100 μm.

For example the heat from the sun reaches the earth via radiation that passes through space and then through the atmosphere of the earth.

CONVECTION:

It is the mode of heat transfer that takes place in a fluid matter. The molecules in this case move from one place to another due to the difference in density developed as a result of heat absorption.

Example, the boiling of water. When the water in a utensil is heated, the heat is supplied at the bottom. In such a case the molecules of the water absorb the heat resulting in increased intermolecular spacing and hence the water at the bottom becomes the least dense in the bulk of water mass in the utensil hence rises up at to the free surface of the fluid mass. Then the densest mass of the fluid occupies the bottom space and is heated by the heat source supplied. This chain continues.

CONDUCTION:

This is the process of heat transfer from one molecule to the next neighbouring molecules. The propagation of heat energy occurs in a sequential manner starting from the molecule nearest to the heat source. The microscopic phenomenon happens in the form of lattice vibrations that are responsible for the transfer of heat energy via conduction.

Example, while heating of a pan the base heats up at first being continuously exposed to heat whereas the handle of the pan being far away from the source heats up after a long time.