whenever an object is heated energy is transferred to its thermal energy store and as temperature increases the process of heating though can take place in three different ways depending on the medium involved for solids heat is transferred by conduction in fluids it's via convection and to get through empty space heat has to be transferred in the form of radiation let's start with conduction the key idea behind conduction is that vibrating particles transfer energy to neighboring particles to understand how this works let's imagine that you were heating one end of a piece of metal with a bunsen burner and imagine the piece of metal as a series of particles as the end of the metal is heated energy is transferred to the metal or more specifically is transferred to the kinetic energy store of the particles at that end this causes the particles to vibrate faster and so they collide with their neighboring particles more often and with more energy as the collisions transfer kinetic energy the neighbors will also vibrate faster and collide more with their neighbors and as this process repeats energy is passed along the piece of metal until in the end the heat is spread out evenly and it will be pretty much the same temperature everywhere now the reason that conduction occurs mainly in the solids is because the particles in a solid are held together really closely which means there's lots of collisions that pass on the energy whereas in liquids and gases the particles are all further apart and so they don't collide as much exactly how well objects transfer energy by conduction is known as their thermal conductivity metals have a high thermal conductivity and transfer heat energy rapidly whereas plastics have a low thermal conductivity which is why we use them as insulators and pretty much all fluids have a low thermal conductivity convection on the other hand occurs mainly in fluids and remember fluids can refer to anything that can flow so both liquids and gases because the particles in fluids aren't fixed once they're heated and they gain kinetic energy they all move around faster by the process of random diffusion this will cause these more energetic particles to move away from the warmer region towards the cooler region and overall this means that the higher energy particles in the warmer region are a lot more spread out than those in the cooler region so effectively the fluid in the warmer region actually expands as it heats up and so it becomes less dense than the cooler fluid to understand how this works in real life let's imagine that we had a container of fluid so that could be either liquid or gas as we heat the container the following things would happen first the particles near the heat source would gain kinetic energy and spread out becoming less dense because they're less dense these particles rise above the colder less dense particles above them and at the same time these cooler particles sink down and take their place whilst this is happening though the hot particles will lose their energy and cool down and the cool particles now the bottom would heat up because of this the cycle would keep on repeating for as long as the fluid was being heated and we call this cycle a convection current we actually see these convection currents all over the place from oceans to inside buildings where radiators warm the nearby air and set off the cycle on the other hand to reduce convection we need to stop the free flow of fluids which is all we're doing when we sleep under a blanket at night which is stopping the warm air from escaping what conduction and convection have in common is that they both involve particles gaining kinetic energy it's just that in conduction only the energy is transferred between the different particles whereas in convection the particles themselves move however heat energy can also be transferred without particles which means it could travel through a vacuum this happens when energy is transferred by radiation and specifically when the energy is carried by infrared waves all objects constantly absorb and emit radiation and in reality they do both at the same time importantly the hotter the object is the more radiations emits this is why it feels hot to put your hand over a barbecue even if you're not touching it the very hot metal and coal is emitting infrared radiation which is absorbed by your hand we take a closer look at infrared radiation when we cover the electromagnetic spectrum anyway that's all for today so hope you enjoyed this video and we'll see you next time