Chapter 2: Thermal Energy Flashcards
What is conduction?
The transfer of energy in solids
How does conduction work?
Neighbouring atoms transfer thermal energy to each other due to their vibrations.
What are some examples of good and poor thermal conductors?
Metals are good thermal conductors. Plastics, but particularly trapped air, are poor thermal conductors.
Why are metals good thermal conductors?
They have delocalised electrons, which collide with ions, transferring kinetic energy to the ions.
How does temperature affect the motion of particles in a substance?
As the temperature rises, there is more energy, and so the particles vibrate.
What is radiation?
The transfer of thermal energy via infrared waves
What objects emit more radiation and what objects emit less radiation?
Matt black emits and absorbs the most radiation, and shiny silver emits and absorbs the least radiation. Hotter objects emit more radiation.
How do you reduce heat loss in a house through windows?
You can use double glazing to reduce heat loss in windows. They have trapped air between two panes of glass, and as it is very thin, there is little convection, and conduction.
How do you reduce heat loss in a house through walls?
Heat loss can be reduced through walls by using cavity wall insulation. Insulating material is blown into the gap between the brick and inside wall. This stops conduction, and as the material stops air from circulating, it also prevents convection.
How do you reduce heat loss through the roof?
You can use loft insulation to reduce heat loss through the roof. Insulating material is put in between the inside roof and the outer roof, stopping conduction and convection.
What is convection?
Convection is the transfer of thermal energy in fluids.
Describe a convection current.
The fluid increases in temperature, expands, becomes less dense and rises. Once away from the heat source, the fluid cools down, contracts, becomes less dense and falls. Cold fluid rushes in to fill the space when warm fluid rises. The whole cycle is then repeated.
