Heat and conduction Flashcards
Describe conduction, convection and radiation
Theatomsof a solid are held together by chemical bonds. The atoms are fixed in place but are free to vibrate.
Explain why materials transfer heat differently
When part of a solid absorbs heat energy the atoms vibrate faster and with bigger amplitude. These vibrations pass from atom to atom transferring heat energy as they do so.
Apply knowledge of heat transfer methods to domestic measures.
This process happens in all solids when heated but is a slow process.
What happens to electrons in metal?
Some of theelectronsin a piece of metal can leave their atoms and move about in the metal as free electrons. When the free electrons absorb heat energy, they move much faster.
Do Electrons have kinetic energy?
As they move through the metal, free electrons crash into metal ions.
Some of thekinetic energyof the free electron is absorbed by the ions and it vibrates faster and with greater amplitude.
What is vibrations ?
This process is very much faster than conduction caused by just passing vibrations from atom to atom.
Is trapping air a good to keep us warm?
The more layers we wear, the more air can be trapped and the warmer we will remain.
what is an insulator in terms of cloths?
Some clothes, such as wool, are excellent insulators, because they trap lots of air between individual fibres.
What is Convection in terms of water
CONVECTION Liquids and gases are fluids because they can be made to flow.
Theparticlesin these fluids can move from place to place.
Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.
This water is in turn heated, expands becomes less dense and rises.
The process continues, a convection current is set up and heat is transferred through the
Conduction explain how it works in a beaker
Heat is initially transferred through the glass wall of the beaker byconduction.
The water in the region of the Bunsen flame is heated.
It expands, becomes less dense and rises.
Radiation is is like conduction or convection ?
RADIATION Unlike conduction andconvection- which need the vibration or movement ofparticles-infrared radiationis a type of electromagnetic radiation.
When infrared radiation is absorbed by an object it is heated and its temperature rises.
Is trapped air a good insulator?
Trapped air is a natural insulator and because it is trapped, convection currents cannot be set up easily. So, trapped air reduces heat loss by conduction and convection. Many insulating materials incorporate trapped air i.e. double glazed windows
Can heat loss through wall be reduced and how?
Heat loss through walls can be reduced using cavity wall insulation. This involves blowing insulating material into the gap between the brick and the inside wall.
Are insulating materials bad conductors?
Insulating materials are bad conductors and so this reduces the heat loss by conduction
It is even possible to fit reflective foil behind radiators. To reduce heat loss by radiation.
