[Music] hi and welcome back to three signs lesson co uk by the end of this video you should be able to interpret Heating and Cooling graphs that include change of state in the last video we looked at the idea of internal energy remember that this is the energy stored inside a system by the particles this includes the kinetic energy of the particles due to their movement and also the potential energy of the particles now the potential energy is due to the forces between the particles and also the bonds between atoms in a molecule so in this video we'll look your heating and cooling graphs so let's get started imagine I've taken a solid substance and I'm gradually heating it and I'm measuring the temperature I get a graph like this now this is called a heating graph so we can see that the temperature of the solids rising as we're increasing the energy in the particles now at some point the temperature stops rising underline becomes horizontal at this point the solid is changing state and turning into a liquid another word it's melting now the energy we're putting in is weakening or breaking the forces of attraction between the particles that's allowed on the substance of change state from a solid to a liquid scientists call the energy needed for a substance change stake the latent heat and we're going to look at latent heat in a later video so doing the change of state we're increasing the internal energy store this system but we're not changing the temperature now the temperature that the substance marks at is the melting point and we can find that by reading off the graph like this eventually all of the solid will have merged into a liquid and now the temperature starts to rise again and again that's because we're increasing the energy of the particles now at some point the temperature stops increasing and the line becomes horizontal again like this at this point the substance is boiling and again the energy we're putting in is weakening or breaking the force of attraction between the particles we can find a boiling point from the graph like this once all of the liquid is boiled the temperature starts to right again now if we take a gas uncool it down we get a graph like this one then it's called a cooling graph again we can see where the change of state take place when the gas changes to a liquid this is called condensation undergoing the liquid changes to a solid this is called freezing remember that you find plenty of questions on heating and cooling grass in my revision work book and you can get that by clicking on the link above ok so hopefully now you should be able to interpret heating and cooling graphs that include change of state [Music] and