Week 2 – Jss 2 Third Term Basic Science Lesson Notes

WEEK2: THERMAL ENERGY {2}
Thermal energy is a term used to describe the energy content of a system related to heating effects such as temperature increase or decrease.

 Transfer of heat energy.
Heat energy can be transmitted in three different ways:
1. Conduction
2. Convection
3. Radiation
1. Conduction: this is the process by which heat energy is transferred from a region of higher temperature to a region lower temperature along a stationary solid material i.e. heat flows from a hot body to a cold body by itself. The heat flows by passing from one particle to the next along the stationary solid material.
The mean position of the molecules or particles of the solid material does not change. Conduction is the only means of heat transfer in solids.

GOOD AND BAD CONDUCTORS.
Good conductors are substances that allow heat energy to pass through them easily. Examples are metals like iron, copper, lead, aluminum and zinc. All metals are good conductors are substances that do not allow heat energy to pass through them easily. They are known as insulators. Examples are: wood, plastics, cotton, cork rubber, ceramics and water. Liquids and gases are poor conductors of heat.

2. CONVECTION: convection is the process by which heat energy is transferred from one part of a fluid [liquid or gas] to another, by the actual movement of the molecule of the fluid. Molecules of water that is being heated acquire energy and rise with the heat energy. The molecules of cool water above sink to replace the molecules of rising hot water at the bottom to become heated. This circulation of the fluid [liquid or gas] when heated is called convection current. Convection occurs in liquids and gases but not in solids. Convection currents are more easily set in gases, because gases expand more readily when heated. Examples of convection in nature include:

1. Land breeze and Sea breeze.
   
2. Wind system.

    3. Radiation: This the process by which heat energy is transferred from one place to another, without the aid of a medium.
   That is unlike in conduction and convection the medium does not play an active part in radiation process. Heat from sun travels by waves through space to the earth by radiation. Dull, black surfaces are best absorbers of heat radiation while brightly polished surfaces are poor absorbers.
   
   EVALUATION:
   1. Mention the three ways in which heat travels.
   2. Define Thermal energy.
   3. State the effect of thermal energy.
   4. Define the following terms: Conduction, Convection and Radiation.