Guidelines for Thermodynamics Jillian Campbell, Karly Johnson, Jared Ostler, Daniel Borbolla

Absolute zero Absolute zero is when atoms and molecules lose all available kinetic energy. No more energy can be extracted from a substance and no further lowering of temperature is possible. Experiments found that all gases, regardless of their initial pressures or volumes, change by 1/273 of their volume at 0 degrees Celsius change in temperature, provided the pressure is held constant. The absolute temperature scale is called the Kelvin Scale. Absolute zero is 0 K. There are no negative numbers on the Kelvin scale. Degree on the Kelvin Scale are calibrated with the same-sized divisions as on the Celsius scale.

Internal Energy Energy within a substance is found in these and other forms, which, when taken together, are called internal energy. It is separated in scale from the macroscopic ordered energy associated with moving objects; it refers to the invisible microscopic energy on the atomic and molecular scale. For example in a book the paper is composed of molecules that are in constant motion. They have kinetic energy. Due to interactions with neighboring molecules, they also have potential energy. The pages can be easily burned, so we know they store chemical, which is really electric potential energy at a molecular level. Vast amounts of energy are associated with atomic nuclei. U is the most common symbol used for internal energy.

1 st law of thermodynamics The First Law of Thermodynamics states that when heat flows to or from a system, the system gains or loses an amount of energy equal to the amount of heat transferred. A system can be defined as a well-defined group of atoms, molecules particles, or objects. This is important because one must be able to differentiate between what is contained within the system and what is outside it. The system can therefore “use” this heat to increase it’s own internal heat if it remains within the system or to do work on it’s surroundings if it leaves the system. The first law of thermodynamics therefore more specifically states that heat added to a system = increase in internal energy + external work done by the system. The first law of thermodynamics is not concerned with the inner workings of the system itself, for it is too complex to be described. Therefore the molecular behavior in the system only serves the two functions described above (internal temperature increase, work done, or both). It is used as a link between the microscopic processes and their macroscopic effects.

Adiabatic processes Adiabatic Process – the compressing and expanding of a gas while no heat enters or leaves the system. (Also known as Isocaloric Processes.) The way that heat is prevented or adiabatic (impassable), is by having thermally insulated the system protecting it from its surroundings. Another way that this heat is kept out is by executing the process fast enough that no time is allowed for heat change, therefore the net heat transfer to or from the system is zero. With adiabatic conditions, changes on the inside of the system are equal to the work being applied on the outside. Δ Heat = Δ Internal Energy + Work No heat transfer Δ Heat = 0 Work = Δ Internal Energy An example is that if we work with a compressing system, its Δ Internal Energy increases which raises the temperature. On the other end, when a gas adiabatically expands, Δ Internal Energy becomes cooler.

Examples of adiabatic processes in our atmosphere: weather convection, inversions An adiabatic process in our atmosphere would be vertical flow of air. When air rises in the atmosphere, it expands because of the loss of pressure and when air expands it cools; but when the air descends, the air contracts and is worked upon so it becomes warmer. Oddly enough there is an inversion, which characterizes the atmospheric conditions opposed from normal. This means that temperature rises when the altitude is increased. This occurs when water vapor in the air absorbs Earth radiation and the sinking of air which leads to contraction and then to heat. This type of inversion happens mostly during high- pressure systems in the wintertime. Some occurrences have been recorded in “the Great Basin region of the western United States,” “the Tropics and in the Polar regions.”

2 nd law of thermodynamics The Second Law of Thermodynamics can be defined as heat of itself never flows from a cold object to a hot object. The direction of heat flow is always from hot to cold. So, heat can never go from being cold to being hot. One good example of this law is heat engines. The definition of a heat engine is any device that changes internal energy into mechanical work. In heat engines, mechanical work can only be obtained when heat flows from a high temperature to a low temperature. When we apply the second law to heat engines, we can say that when work is done by a heat engine operating between two temperatures, T hot and T cold, only some of the input heat at T hot can be converted to work, and the rest is expelled at T cold.­

Entropy Entropy is the idea of lowering the “quality” of energy and is defined as the measure of the amount of disorder within a system (ΔS = ΔQ/T). More entropy means more degradation of energy. Energy tends to degrade and disperse with time, therefore the net amount of entropy in any system tends to increase with time. The reason the term net is used is because there are some regions within a system have concentrated or organized energy. This occurs in living organisms who extract energy from their surroundings and use it to increase their own organization, resulting in an increase of entropy on the small level of the organism. However, this decrease of entropy within the living organism occurs at the expense of an increase of entropy on an overall net level. When energy isn’t being transformed into the living organism to very well, the organism dies. This can otherwise be stated that entropy in the universe is always increasing.

References astr.gsu.edu/hbase/thermo/inteng.html astr.gsu.edu/hbase/thermo/inteng.html adiabatic_process.html adiabatic_process.html net.org/~esati/sdcea/appliedmet2.pdf net.org/~esati/sdcea/appliedmet2.pdf ss/14312_44.htm ss/14312_44.htm