The Meaning of Thermo

The sun emits electromagnetic radiation such as visible light and other spectra we cannot observe. A car's exhaust pipe is heated from the gas coming from the engine. A runner's shoes heat as their feet push off the ground. Heat is everywhere! It is integrated in our everyday lives and we rely on its existence for survival.

Now this study of heat is what's known as thermodynamics.

Energy

Thermodynamics allows us to analyze energy which is often described in many different forms. These forms include

• Kinetic Energy - associated with the movement of objects.
• Potential Energy - associated with compression/tension, gravitational attraction, and electrical repulsion/attraction.
• Internal Energy - the sum of all microscopic forms of energy in a system; this includes the kinetic energy of molecules and the energy stored in their molecular bonds.

Now energy cannot be created or destroyed, but it can change form. This is known as the first law of thermodynamics. Energy is continuously transferred. As a person climbs a hill, they break down the chemical bonds in the food they consumed to give them energy which they use to attain kinetic energy. Now as this person's elevation climbs (pun intended), they may slow and their kinetic energy is converted into potential energy. However, not all of this spent kinetic energy is transferred into potential energy. Some of which is lost as heat energy coming from the person's body, or energy dissipated by the friction of their foot with the ground.

Energy also has a factor of quality. The hotter the process is, the better quality it has. This is known as the second law of thermodynamics.

Units

Another thing that is important in the study of thermodynamics is units. With all equations, they must satisfy dimensional homogeneity; this means each side of an equation must have the same unit, unless both sides are unitless. There are 4 fundamental dimensions: mass (m), length (l), time (t), and temperature (k). All equations are built upon these fundamentals.

For example, pressure has units of $ \frac{N}{m^2} $ or Netwons per meter squared in SI units. A Newton has units of $ \frac{kg • m}{s^2} $ which can be written as $ \frac{m •l}{t^2} $ in fundamental units. Hence, the fundamental units for pressure can be written as $ \frac{\frac{m •l}{t^2}}{l^2} = \frac{m}{l•t^2} $. This may seem odd to analyze at first, but they are many benefits to unit analysis. One example of this is with Buckingham Pi Theorem at which we can use to derive important nondimensional numbers such as Reynolds number or Mach number!

Now that we have a starting understanding of thermodynamics, will we continue to dive deeper into the properties and states of a system.