If a substance is so viscous that its rigid, we call it a solid, otherwise we call it a fluid. And if a fluid isn't compressible, we call it a liquid, otherwise we call it a gas or plasma, depending on how well it conducts electricity.

Thermodynamics: the science of energy. From the Greek therme (heat) and dynamis (power)

Fluid Dynamics (subdiscipline of fluid mechanics): describes the flow of fluids- liquid and gas

  • Hydrodynamics- flow of fluids with virtually no density change (flow of liquids, or gas at low speed)

  • Gas dynamics- fluids that undergo significant density changes (high-speed flow of gas through nozzle, movement of body through low density air of the upper atmosphere)

  • Aerodynamics- flow properties of air past a solid body


Energy: the ability to cause changes. Conservation of energy principle: during an interaction, energy can change from one form to another, but the total amount of energy remains the same- Energy cannot be created nor destroyed.


1st Law of Thermodynamics

The net change (increase or decrease) in the total energy of the system (quantity) during a process is equal to the difference between the total energy entering and the total energy leaving the system during that process.

2nd Law of Thermodynamics

States that the total entropy of an isolated system can never decrease over time. The total entropy of a system and its surroundings can remain constant in ideal cases where the system is in thermodynamic equilibrium, or is undergoing a (fictive) reversible process. In all processes that occur, including spontaneous processes, the total entropy of the system and its surroundings increases and the process is irreversible in the thermodynamic sense.

Provides the necessary means to determine the quality as well as the degree of degradation of energy during a process (ex completion of chemical reactions).

3rd Law of Thermodynamics

The entropy of a perfect crystal is zero when the temperature of the crystal is equal to absolute zero (0 K).

Perpetual motion machine- is any device that violates the first or second laws of thermodynamics

Newton's 1st Law of motion

States that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. It may be seen as a statement about inertia, that objects will remain in their state of motion unless a force acts to change the motion.

2nd Law of motion

Pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. F=ma

3rd Law of motion

For every action, there is an equal and opposite reaction.

Closed system (controlled mass): fixed amount of mass, and no mass can cross its boundary, but energy can

Open system (controlled volume): both mass and energy can cross the boundaries (real and imaginary)

Steam Power Plant- Thermal Efficiency = Net work output/ Total heat input