Previously, we have pondered over some of the forms of energy; one of them is heat.

Heat is nothing but thermal energy. In this guide, we will focus on the three ways in which heat (thermal) energy is transferred:

  • Conduction
  • Convection
  • Radiation
Type of heat energy transfer How it works Example
Conduction

 Notes: Some substances are good conductors and some are bad; this is judged by finding the ability of the material’s molecules to pass on the energy through vibrations.

Occurs when the heat energy causes molecules to become energetic and vibrate violently; this causes their energy to be passed through vibrations to other molecules and thus rapidly throughout the material. Metals (the hotter the metal, the more kinetic energy it will have, hence the greater the conduction
Convection

Occurs when particles can move around freely in a liquid or a gas.

Hot gas is always less dense and so, it moves upwards in a room, replacing the cool gas there. Hence, convection currents set up.

A heater in a room

 

Potassium (VII) permanganate

 

Radiation All objects absorb and emit infrared radiation. The hotter the object is, the greater its thermal radiation would be.

Infrared radiation is a part of the electromagnetic spectrum and it is transferred in the form of infrared waves (which has a long wavelength). It plays a crucial part in the greenhouse effect on earth.

Some surfaces are better at absorbing and emitting radiation. These are:

1.    Shiny surfaces are the best reflectors.

2.    Shiny surfaces are the worst absorbers.

3.    Matt black surfaces are the best absorbers.

4.    Matt black surfaces are the worst reflectors.

5.    Matt black surfaces are the best emitters of infrared radiation.

The Greenhouse effect

 

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