 So, welcome back. So, after having understood the PT diagram where the phase transitions lines are given where the phase transition can be understood. Let us now see the phase change processes that takes place when you got a phase transition from solid to liquid and liquid to vapor. So, here you can see I have plotted a PT diagram with the cricket y as I referred to earlier. Also on the right side I showed a triangle and I have just placed solid, liquid and gas phases on the 3 vertices of this triangle. What I want to show you now here are the phase change processes from solid to liquid, liquid to vapor, solid to vapor and what are different names for these processes which most of you know. So, we know in this cricket y or a PT diagram we have got solid here, liquid here and vapor here. Similarly I have shown solid, liquid and gas at these points of the vertices of this triangle. Let us now see solid to liquid phase change process alright. So, I have got one point in solid region, I have got second point in liquid region and this phase transition will happen if I go on increase the temperature. If I increase the temperature from solid to liquid region this is the process that takes place and we know that it is called melting alright. So, when the temperature increases the solid will get converted to liquid form and this process would happen across this SL saturation line during which latent heat will come also into existence. On the right side I have shown this from solid to liquid that is what the process looks like over here. While if I reduce the temperature of this liquid it will get solidified it will the process is reverse of melting and that is what we call as freezing. Again this process would happen across this SL saturation line solid to liquid saturation line melting and freezing are two opposite processes that are shown in this triangle also. Let us now look at liquid to vapor phase transition all of you know these processes very well we are just naming those processes which are actually standard processes. So, this phase change process from liquid to vapor would happen when again the temperature increases of the liquid and this is what we call as vaporization alright. Again I have shown it here on this triangle liquid to gas or liquid to vapor phase change process. If now I have got a vapor over here and if I decrease the temperature of this vapor what you will get is conversion of this vapor into liquid and this reverse of vaporization is what we call as condensation alright. So, again we have got vaporization and condensation as two reverse processes between liquid to gas or liquid to vapor phase change. Let us now come to solid to vapor phase change process. If this point lies at a low pressure region and low temperature region and if I increase the temperature solid can get directly transformed into vapor and this process as you all know is called as sublimation. So, solid to vapor phase transition that will happen across this SV phase transition line or SV saturation line and reversal of this would what we call as de-sublimation. So, this is the process which is shown on this triangle also here solid to gas solid to vapor is what we call as sublimation and the reverse is called as de-sublimation. So, all these processes of phase change occur across these phase change lines solid liquid, liquid vapor and solid vapor of these three lines of this crooked y. So, I have shown here all the three processes melting freezing vaporization condensation sublimation and de-sublimation occurring from solid to liquid region, liquid to vapor region and solid to vapor region respectively. All this can be seen again over here in this triangle, but important to understand that these processes happen across this phase transition line which are actually demarcated. All these phase change processes involve latent heat while conversion and also during these phase changes they go through a presence existence of two phase mixture as what we had seen earlier in the phase diagram of water. Thank you very much.