Heat Flashcards
In what direction does heat energy flow
Heat energy always flows from hot to cold
State the energy transfer processes (heat)
Conduction
Convection
Infrared radiation
Evaporation
Condensation
What are the factors that affect the rate at which heat energy flows
The factors that affect the rate at which heat energy flows:
The temperature difference between the two objects
The surface area of an object
The colour of the object
What happens when the temperature of an object increases, in terms of internal energy
When the temperature of an object increases, the energy stored in the object increases (the object’s internal energy increases)
This is because heating causes energy to be transferred to an object’s particles, this increases the kinetic energy store of the particles causing them to move faster. This results in an increase in internal energy, which causes an increase in temperature
Complete the sentence
The energy stored in an object is called its ____________
The energy stored in an object is called its internal energy
Define internal energy
Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.
State the ways in which energy can flow
Energy can flow by:
Conduction
Convection
Infra-red Radiation
Condensation
Evaporation
Complete the sentence
The more delocalised electrons, _____________
Complete the sentence
The more delocalised electrons, the higher the rate of conduction
What does a high thermal conductivity mean in terms of energy transfer in a metal
The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across that material
Define conduction
A method of energy transfer by heating where vibrating particles transfer energy through a material by colliding with neighbouring particles and transferring energy between their kinetic energy stores
In what type of material does conduction occur in
Conduction occurs in solids
What type of materials are the best insulators
Non-metal materials such as wool and fibreglass are the best insulators
What type of material is the best conductors
Metals are the best conductors
What is a fluid
A fluid is a gas or a liquid
Explain the process of conduction through metals
The metal has delocalised electrons
The delocalised electrons gain energy when the metal is heated and move faster through the metal.
The delocalised electrons collide with other electrons transferring kinetic energy to them.
This increases the internal energy of the metal causing an increase in temperature.
Explain the process of conduction through non-metals
The heat energy is conducted from the hot end of the object to the cold end of the object
It is transferred from atom to atom.
The atoms in the part of the object being heated vibrate faster and collide with each other more.
The collisions cause energy to be transferred between the atoms’ kinetic energy stores.
This process continues throughout the object until the energy is transferred to the other side of the object.
It is then usually transferred to the thermal energy store of the surroundings (or anything else touching the object)
Energy is transferred by conduction through the metal pan handle
Energy is transferred by conduction through the pan to the water
Why are all metals good conductors of heat (and electricity)
Metals have delocalised electrons.
These electrons can travel through the metal, transferring the energy more quickly
Why are metals better conductors of heat (and electricity) than non-metals
Metals have delocalised electrons.
These electrons can travel through the metal, transferring the energy more quickly
Non metals do not have delocalised electrons and pass on (transfer) heat energy by the vibrations of atoms. This process is very poor.
Define convection
Convection is a method of energy transfer by heating in liquids and gases in which energetic particles move away from hotter regions to cooler regions
Describe the process of convection
When the air/liquid is heated, the particles gain energy.
Therefore they move faster and their separation is further, causing a decrease in density.
Less dense and hotter air/liquid will rise above the more dense, colder air/liquid.
The cold, more dense air/liquid takes the place of the hotter, less dense air/liquid and the process continues
In what types of material does convection occur
Convection occurs in fluids (anything that can flow) - gas or a liquid
What is infra-red radiation
Infra-red radiation is the transfer of heat energy by an electromagnetic wave.
In terms of radiation, what do all objects do.
All objects continually emit and absorb infra-red radiation
Complete the sentence
Energy is _________ being transferred to and from ___________ (emitted and absorbed), even through empty space (a __________)
Complete the sentence
Energy is continually being transferred to and from objects (emitted and absorbed), even through empty space (a vacuum) - they do both at the same time
