 Welcome back, now we are going to look at temperature scales in detail and the consequence of defining temperature scales, the equations of state of various types of systems. We are going to quickly review the Celsius scale of temperature which we saw earlier. Then we are going to look at gas thermometer, which allow us to increase the range of temperatures that we measure. Then an experimental law discovered by Boyle, Boyle's law we will discuss. And from that we get the idea of the ideal gas. And the behavior of an ideal gas gives us a standard set of scales of temperature known as ideal gas scales of temperature. Out of this, one is considered now the standard which we always use. This is the ideal gas Kelvin scale. Now we will notice that when we study the ideal gas Kelvin scale, that definition automatically leads to what we call the equation of state of an ideal gas. Then we will quickly look at the gas constant and the so-called universal gas constant. Then we will study briefly the properties of an ideal gas which will obey not only the Boyle's law but also another law known as the Joules law. And then we will define the specific heats Cp and Cv. Thank you.