Introduction

The Energy Story

  Energy Is Born
  Energy Types
  Energy Changes
  Energy Generation

The Energy Problem

  Conservation of Energy
  Aging of Energy
  Finite Resources
  The Oil "Crisis"
  Energy Pollution
  Discussion Topics

The Energy Solution

  Conserving Electricity
  Appliance Efficiency
  Heating Conservation
  Renewable Energy

Web Links

Teacher Guide

About the Author


Secret Lives Title - The Energy Story


agif - flames
The Ten Types
Heat Energy


There are two major types of heat energy - sensible heat and latent heat.

Sensible heat is due to the kinetic energy or the motion of atoms or molecules in a substance. As this motion increases, the temperature also increases. So the amount of sensible heat energy contained in a substance is directly related to its temperature.

The simulation on the website below clearly illustrates this relationship between temperature and the kinetic energy or velocity of the molecules in a substance.

Move the slider to increase the tempeature and see the associated increase in the velocity of the molecules.

Latent heat is the energy given off or absorbed during a change of phase. Whenever a substance changes form a gas to a liquid or from a liguid to a solid this latent heat is given off. Whenever a substance changes from a solid to a liquid or from a liquid to a gas this latent heat is absorbed from the surroundings. While a substance is changing phase, no temperature change takes place. So as heat energy is added to or removed from a substance, this heat energy is going either to sensible heat (temperature change) or to latent heat (phase change), but not both at once.

Your body uses latent heat during the summer as it sweats. As the persperation evaporates, the vapor absorbs this latent heat of vaporization from your body, cooling it.

The latent heat of steam (water in the gaseous phase) is very high. This makes steam an ideal subsatnce to transfer large amounts of energy, both the latent heat as a gas, and as sensible heat due to its high temperature.