 Welcome back Mechanical AI. Did you know that expansivity and compressibility are the deciding factors for the application of a certain fluid? This makes us wonder, what is expansivity and compressibility? Before we jump in, check out the previous part of this series to learn about the thermodynamic relations. Now, expansivity or more technically volume expansivity is the fractional increase in volume of a solid, liquid or gas per unit rise in temperature. That is Vf equals Vi into 1 plus gamma theta, where gamma is a cubic expansivity which is equal to 3 alpha, alpha here being the coefficient of thermal expansion. Isothermal compressibility also known as coefficient of compressibility or simply compressibility is a measure of the relative volume change of a fluid or solid as a response to a pressure or mean stress change. It is denoted by beta. The credit of uniting these quantities goes to Julius Robert Mayer. He derived a relation between specific heat at constant pressure and the specific heat at constant volume with coefficient of thermal expansion and isothermal compressibility. This relation in his honor is called the Mayer's relation. Hence we learned about what expansivity is and then about what compressibility is and then saw them relate to each other using Mayer's relation. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also thanks a lot for those constructive comments. You help the channel grow. So here are the top mechanical years of our last videos. In the next episode of Mechanically AI, find out what availability is.