Unit 10: Thermal Energy Flashcards
What is temperature?
Temperature refers to how hot or cold and object is. It is a measure of the average kinetic energy per particle.
How does temperature flow?
Temperature flows from a hotter region to a colder region.
What is thermal equilibrium?
Thermal equilibrium is achieved when both regions are at the same temperature and there is no net flow of thermal energy.
What is conduction?
Conduction is the transfer of thermal energy through a medium without any flow of the medium.
Describe conduction in a non-metal.
The rod is heated at one end, causing the particles there to gain thermal energy and vibrate vigorously. These particles will collide with neighbouring particles and transfer energy to them.
Describe conduction in a metal.
The rod is heated at one end, causing the particles there to gain thermal energy and vibrate vigorously. These particles will collide with neighbouring particles and transfer energy to them. The free-moving elections in the metals will diffuse from the hotter region to the colder region.
What is convection?
Convection is the transfer of thermal energy by the movement of a fluid due to density.
Describe the formation of a convection current in a container that is being heated by a metal plate.
When the water at the bottom of the container is heated, it expands. The mass of the water remains the same, but it’s density decreases, causing it to rise. The cooler water at the top, being denser than the rising hot water, sinks to the bottom of the container. The process repeats itself, forming a convection current.
What is radiation?
Radiation is the transfer of thermal energy in the form of infrared radiation without the aid of a medium.
What are the characteristics of a white/silver and smooth surface?
It is a poor radiator of infrared radiation, a poor absorber of infrared radiation and a good reflector of infrared radiation. Thus, it causes objects to cool down and heat up slowly.
What are the characteristics of a black and dull surface?
It is a good radiator of infrared radiation, a good absorber of infrared radiation and a poor reflector of infrared radiation. Thus, it causes objects to cool down and heat up quickly.
How do the various features of a vacuum flask minimise heat transfer through convection, conduction and radiation?
(a) The vacuum between the glass walls prevents the transmission of thermal energy by conduction and convection.
(b) The silvery surfaces within the double glass walls minimises the transmission of thermal energy by radiation.
(c) The glass wall, the foam support and the plastic cap are all poor conductors. They reduce the transmission of thermal energy by conduction.
(d) The cap also reduces the transmission of thermal energy through convection and prevents thermal energy loss through evaporation.
