Thermal Insulation (Edexcel GCSE Combined Science) : Revision Note

Thermal Insulation

• Thermal energy transfers from hotter areas to cooler areas by the processes of:

  • Conduction

  • Convection

  • Radiation

Conduction, convection and radiation demonstrated in a mug of hot tea

• Objects will always lose heat until they are in thermal equilibrium with their surroundings

• Thermal equilibrium is reached when objects have cooled to room temperature

• Insulation can be used to reduce the rate at which heat transfers

Reducing Conduction

• Insulators are materials that are poor conductors of heat

• Fabrics, such as wool and cotton, are good insulators

Different materials have different properties of conductivity

• These materials are usually low density and often contain pockets of trapped air

  • This makes them very effective because air is a poor conductor

• Surrounding a warm object with a material that contains trapped air will reduce the rate at which it loses heat

• Likewise, surrounding a cold object with such a material will reduce the amount of heat reaching the object

Reducing Convection

• Insulating materials that contain trapped air are also effective at reducing convection

• Trapped air is unable to move around, forming convection currents

• By placing a lid on a hot drink, or saucepan, convection can be further reduced

Reducing Radiation

• Infrared radiation is emitted from all hot materials

  • It is a wave of electromagnetic radiation

• Shiny materials are poor emitters of radiation

• By covering the material with a shiny (non-metal) coating the rate of heat loss can be further reduced