conduction, convection, radiation p2

• Conduction involves the transfer of thermal energy through the particles of a substance by direct contact.
• A good conductor has high thermal conductivity, while a poor conductor has low thermal conductivity.
• a good insulating material will trap lots of still air inside its structure so that less heat can be conducted away from your body
• the insulator in a jumper are the wool fibres + air that is trapped between the fibres
• increasing the temperature of a liquid affects the rate of evaporation (increases)
• increasing the surface area of a liquid affects the rate of evaporation (increases)
• an object hotter than its surroundings will emits more radiation EVERYY second than it absorbs, to cool down
• all objects emit and absorb infra-red radiation, but the amount of radiation emitted depends on the temperature of the object
• infrared radiation is a type of electro-magnetic radiation that has similar properties to visible light but has a wavelength slightly longer that of visible red light
• convection currents occur in liquids and gases where the particles, get heated and rise to the top where they soon cool down and sink back to the bottom
• since metal is a great thermal conductor is has high thermal conductivity. when your body reaches contact with the metal, energy is transferred
• graphite is a non-metal but it is a good thermal conductor because one of its outer electrons is free to move around.
• materials that are poor conductors of heat are known as insulators.
• non-metals are poor conductors of heat and electricity, they are brittle and have low melting and boiling points
• metals are good thermal conductors because they have a 'sea of delocalised electrons' that are free to move throughout the metallic structure
• in conduction, when particles gain more energy and transfer it through vibrations - moving quicker and quicker.
• metals are good conductors because they allow energy to 'travel through them' easier.
• in conduction, when particles gain more energy and transfer it through vibrations - moving quicker and quicker.
• metals are good conductors because they allow energy to 'travel through them' easier.
• metals have delocalised electrons which are able to move around and transfer energy quicker.
• during conduction, a substance is heated and its particles gain MORE energy. causes them to vibrate more and collide with near-bye particles
• conduction is the transfer of energy by heating - between substances that are in DIRECT CONTACT with each other
• a delocalised electron can leave the atom but not the metal - during conduction
• conduction is a method of energy transfer in SOLIDS
• when an object is heated, the atoms/molecules inside it start to vibrate faster and faster. this means that they get closer together and further apart as they vibrate. if two objects are touching then some of these fast moving molecules will hit another object and pass on their kinetic energy (heat). this process continues until all the heat has been transferred from one object to another.
• the rate at which something transfers heat depends on how many particles there are and how much energy they have. metals like copper or aluminium have lots of free electrons so they can carry away large amounts of energy quickly. this makes them very good conductors of electricity and heat.
• in conduction the particles vibrate faster so they collide with their neighbours more often which causes them to transfer some kinetic energy to those neighbouring particles.
• energy can be transferred from a hot object to a cold object by:

  • conduction
  • convection
  • radiation