Conduction and Convection Flashcards
Name an example of a good thermal conductor & why?
Metals - their particles are close together in a regular pattern so vibrations are passed on easily
Why is the handle of a kettle made of plastic?
Plastics are poor conductors, as their particles don’t have a regular pattern, therefore energy is transferred very slowly.
This means, that the heat from the kettle is not passed onto the handle so it is safe to hold.
Why are liquids and gases poor thermal conductors?
> The particles in liquids are not in a regular arrangement so it is difficult for conduction to occur.
In a gas, the particles are far apart so they cant pass on energy very easily
How is energy transferred through solid materials?
By conduction:
>Particles are always vibrating, but in a fixed position
>When they get hotter they have more energy and so vibrate more
>The particles collide with other particles
>Kinetic energy is transferred
>Energy is conducted
What is a thermal insulator?
A material that does not conduct heat very well and transfer heat slowly
Give two examples of thermal insulators?
Wood and plastics
Why is wood not a good conductor?
The particles are close together, but the pattern is not regular so energy is passed on slowly.
How can free electrons pass on energy?
They gain kinetic energy form collisions, and are able to travel through the material.
Metal has free electrons and these can be used to conduct electricity.
What is convection?
When particles carry energy from one place to another
What is an example of convection?
Hot air rises and is replaced by cold air
How is energy transferred in gases?
When particles of air gain more energy, they move faster and that part of the air expands.
The density of this region of air decreases because there is the same number of particles, but in a larger space.
Describe the movement of a convection current?
The cooler fluid nearby is denser than the heated fluid.
The denser cooler fluid falls to the bottom, and the less dense hotter fluid rises.
What could prevent convection current and loss of heat in the home?
Cavity walls
