Thermodynamics

Thermodynamics Lab (Division C) and Keep the Heat (Division B) are slated as national events in the 2011-2012 season. Keep the Heat was formerly run as a trial event in Minnesota, replacing Egg-O-Naut because Minnesota winters are too cold to run outdoor events involving liquid water.

Overview
In this event you create a model or device that simply insulates a 250ml Pyrex beaker filled with 100ml of hot water. Your goal is to create a device that loses the least amount of heat after a period of time determined by the instructor (20-30 minutes). While your device is being tested you take a short test on heat (conversions, specific heat, etc). The starting temperature can be anything from 50 degrees Celsius to 90 degrees Celsius (determined by the instructor). Participants will also need to estimate the amount of heat lost according to graphs made prior to the competition (see "Construction").

Device
The Thermo Lab device must fit inside a 30cm cube. If it does not fit, the device will be disqualified. The beaker must be a 250ml Pyrex beaker and it must be easily removable. There should also be easy access to the interior of the device for temperature measurement by the instructor. Plugs are allowed as well as covered loose fiberglass.

Construction
Prior to the competition, competitors should make cooling curve graphs for various starting temperatures so they can easily identify the final temperature at the competition.

Test
The Thermo Lab test can have many different things on it. A Thermo Lab test may include (but is not limited to): temperature conversions, definitions of heat units, heat capacity, and specific heat calculations. No notes or resources may be used on this test. You are allowed a nonprogrammable-nongraphing calculator.

Basic Thermodynamics
Thermodynamics is the study of thermal energy along with how it interacts with matter and energy (Another definition is Lord Kelvin's, and that is: "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency.")

The Four Laws of Thermodynamics
There are four basic laws of thermodynamics that apply to any situation that meets the requirements of the specific law (Although the laws actually start with the zeroth law and end with the third since the zeroth law was created later).

Zeroth Law of Thermodynamics: "If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other."


 * This law is rather self explanatory, but it can be represented in math as: if $$a=c$$ and $$b=c$$, $$a=b$$.

First law of thermodynamics: "A change in the internal energy of a closed thermodynamic system is equal to the difference between the heat supplied to the system and the amount of work done by the system on its surroundings."


 * This basically means that if a closed system receives more net heat than net work that it does, it would gain internal energy, and if the net work exceeds net heat intake, the closed system would lose energy (This can be represented in mathematics where i=change in internal energy, h=net heat intake, and w=net work as: $$i=h-w$$, and that means that when $$h>w$$, $$i>0$$. In addition, $$i<0$$ when $$h<w$$, and $$i=0$$ when $$h=w$$.) One factor that supports this law is the Law of conservation of Energy.

Second Law of Thermodynamics: "Heat cannot spontaneously flow from a colder location to a hotter location."


 * This law explains entropy in that as the temperature of one object nears the temperature of another object, the amount of entropy increases increases, and this entropy must be decreased in order for work to be done. One example for this is a steam engine. As a steam engine is used, the metal and water in the steam engine will retain heat until the temperature of the metal and water is equivalent to the temperature of the fire that they are above. This waste heat can be removed by either the usage of cooling water or shutting the steam engine down until it cools down to a fair temperature.

Third Law of Thermodynamics: "As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value."


 * The importance of this law is that it proves that it is impossible for an object reach absolute zero. The reason for this is that as an object reaches lower temperatures, the molecular/atomic process slow which decreases heat transfer while the amount of work done (In this case it is molecular in the form of heat transfer.) decreases in an asymptotic approach and exponential decay due to the First and Second Laws of Thermodynamics. One example of this is that if there was an object at absolute zero touching another object that is significantly warmer, the warmer object would lose temperature in ever decreasing amounts as there is less energy for the warmer object to give to the colder object (The colder object also gains energy due to the Law of Conservation of Energy and would have less of a potential to receive energy.). That allows both of the objects' temperatures to be tracked using an exponential decay graph for the warmer object and a graph of exponential growth for the colder object (with temperature as the y axis and time as the x axis), and both graphs would have an asymptotic approach toward a certain temperature value (This situation is like constantly dividing 1,000,000 in half in an attempt to reach zero.). That means that an object can never be at absolute zero unless an object can be at a temperature lower than that (which is impossible due to the definition of absolute zero). This also implies that two objects that start out at different temperatures will never reach exactly equal temperatures, but measurement tools don't necessarily have the accuracy to detect those small differences.

Note: The wording of the laws is the specific wording used in the Wikipedia article for thermodynamics.

Joule's Laws
Joule's Laws are two laws created by James Prescott Joule that describe the heat dissipation of components in an electrical circuit and how the internal energy of an ideal gas relates to temperature, pressure, and volume.

Joule's First Law: "$$Q=I^2\cdot R\cdot t$$"


 * In that equation, Q is the heat dissipation of the component while I is the electrical current through the component, and R is the electrical resistance of the component while t is the time that the electricity ran through the component. If the time is measured in seconds (s is oftentimes used as the variable for seconds.), the variable Q will represent an answer in Joules (j). Joule's first Law provides one way in which Electrical Engineering and Thermodynamics relate. In Electrical Engineering, the equation for finding the power in a circuit/component is: $$P=V\cdot I$$ (where P is power in watts, V is volts, and I is current or amperes.) which can be written as $$P=I^2\cdot R$$ (where R is the electrical resistance). That means that: $$J=P\cdot s$$ (W can also be used in place of P.). This can be further proven by one definition of a volt ($$V=J\div C$$ where C represents Coulombs). One Ampere (amp) is equivalent to one Coulomb per second which means that the equation can be changed to: $$V=J \div (I\cdot s)$$ or $$J=V\cdot I\cdot s$$ which is equal to $$J=P\cdot s$$. The main importance of Joule's First Law is that it allows people to calculate the heat dissipation of electrical circuits/components.

Joule's Second Law: "The internal energy of an ideal gas is independent of its volume and pressure, depending only on its temperature."

Note: The wording of the laws is the specific wording used in the Wikipedia article for Joule's Laws.

Thermodynamic Systems
A thermodynamic system is region of the Universe with specific boundaries that is analyzed using thermodynamic theories, principles, and laws.

Everything that is not part of a thermodynamic system is said to be in the surroundings. The system and surroundings are separated by a boundary that may be fixed (always stays in the same spot), movable (location can change), imaginary (There is nothing separating the surroundings and the system, and the boundary is merely a designated space.), or real (The boundary is a physical object.)

There are three types of thermodynamic system, and each type allows different things to pass through the boundary. The types are:

Open System: In open systems, matter, heat, and work can cross the boundary to enter or exit the system. The First Law of Thermodynamics when applied to an open system is (quoting from Wikipedia): "the increase in the internal energy of a system is equal to the amount of energy added to the system by matter flowing in and by heating, minus the amount lost by matter flowing out and in the form of work done by the system."

Closed System: In a closed system, heat and work can cross the boundary, but matter can't cross the boundary. In addition, there is a type of boundary that may be in a closed system that heat can't cross, adiabatic, and one that work can't cross, rigid.

Isolated system: In an isolated system, neither matter, heat, or work can cross the boundary. Therefore, differences in thermal energy will typically lessen until the system reaches thermodynamic equilibrium.

Branches of Thermodynamics
There are several branches of thermodynamics, and each branch is about a specific aspect of thermodynamics.

Classical Thermodynamics


 * This is thermodynamics on a large or macroscopic scale. This branch of thermodynamics is used to model states and processes that are based on properties that can be measured, defined, and examined in a laboratory. These models include models based on the Four Laws of Thermodynamics and include: energy, mass, work, and heat exchanges.

Statistical Thermodynamics


 * This is thermodynamics on the molecular/atomic scale. This branch of thermodynamics explains how microscopic events, properties, and interactions influence Classical Thermodynamics.

Chemical Thermodynamics


 * This branch of thermodynamics is about how energy, within the subject of thermodynamics, influences chemicals and chemical reactions.

Equilibrium Thermodynamics


 * This branch of thermodynamics is about how matter and energy in a system change as the system approaches thermal equilibrium. One main goal in Equilibrium Thermodynamics is to figure out what a system will be like when it reaches thermodynamic equilibrium if you know the starting parameters for the system and the laws/forces that will act upon it.

Non-Equilibrium Thermodynamics


 * This branch of thermodynamics is the study of systems that aren't in thermal equilibrium, and many of the laws/theories/concepts are more general than the ones in Equilibrium Thermodynamics.

Vocabulary
Internal energy: The energy of the motions of atoms and molecules within an object (includes potential energy of molecules and atoms in liquids and solids). Temperature is the measure of the internal energy of an object.

Entropy (when applied to thermodynamics): The amount heat that can't be used to do work.

Absolute Zero: The temperature at which all processes stop (defined in the third law of thermodynamics). This temperature is: 0 degrees Kelvin, -273.15 degrees Celsius, or -459.67 degrees Fahrenheit.

Thermal Equilibrium: When an object/system has an unchanging uniform temperature or when there is no exchange of heat when two objects/systems can exchange heat (In other words, they have the same temperature.).

Thermodynamic Equilibrium: When there are no net flows of matter or energy to or away from a system and no net changes in the matter and energy in that system.

Joule (J): A unit of work equal to: $$N\cdot m$$, $$(kg\cdot m^2)\div s^2$$, $$P\cdot s$$, $$V\cdot I\cdot s$$, $$V\cdot C$$, and $$I^2\cdot R\cdot s$$ (where N=Newtons, m=meters, kg=kilograms, s=seconds, P=watts, V=volts, I=amperes, C=Coulombs, and R=resistance in Ohms.).

Volt (Voltage, V, E): The energy required to move electrons from one location to another divided by the charge of the electrons in Coulombs. Can be stated as: $$V=I\cdot R$$, $$V=J\div C$$, and $$V=W\div I$$.

Coulomb (C): The charge of an electrical current of one ampere in one second or the absolute value of the electrical charge of about 6.24*10^18 protons or electrons (with protons having a positive charge and electrons having a negative charge).

Ampere (Amp, I): The electrical charge of one coulomb in one second (mathematically: $$I=C\div s$$)

Resistance: The amount that an object resists the flow of electric current (found using: $$V=I\div R$$)

Watt (P or W): The Electrical Engineering unit for power that is equivalent to one joule per one second or one volt in a current of one ampere ($$P=J\div s$$ and $$P=V\cdot I$$).

Links
http://www.minnesotaso.org/Files/KEEP%20THE%20HEAT.pdf

Wikipedia-Thermodynamics

Hyperphysics-Thermodynamics

Wikipedia-Joule's Laws