Transfer of heat energy and its effects Flashcards
What is temperature?
Temperature is the measure of degree of hotness and is measured in degree celcius.
What is heat?
Heat is the measure of the thermal energy contained in an object and is measured in joules.
Describe conduction
It always flows from a region of high temperature to a region f low temperature.
Describe conduction in solids.
When part of a solid absorbs heat energy, the atom vibrate faster and with bugger amplitude. These vibrations pass from atom to atom transferring heat energy as they do so.
Describe convection in a liquid.
Heat is initially transferred through the glass wall of the beaker by conduction. The water in the region of the Bunsen Burner flame is heated. It expands, becomes less dense and rises. It is replaced by the cooler, denser water which surrounds it. This water is in turn heated, expands becomes less dense and rises. The process continues, and a convection current is set up and heat s transferred through thee liquid.
Describe convection in gases.
Air close to air conditioner is cooled. It contracts, becomes denser and sinks. It is replaced by warmer, less dense air from the bottom of the room. This air is in turn cooled, contracts becomes denser and sinks. The process continues, a convection current is set up and the entire room is cooled.
A can of boiling water is painted white and black on each side. Which hand feels hotter? Why?
The black surface is a better radiator of heat.
Why did the cork on thee right side fell first?
Heat from the candle reaches both discs via radiation. Since the black disc is a better absorber of heat. It absorbs heat from the candle at a faster rate and melts the wax and its cork drops off first.
How does the vacuum flask keeps its contents warm and its contents cold?
It has a plastic cap at the top. The inner flask consists of a double-walled glass vessel with a vacuum between the walls. The inner walls f the flasks are coated with a thin layer of silver. Vacuum reduces heat via convection and conduction. Silver layer reduces heat loss via radiation.
