Thermodynamics is a Study of heat. A major topic of in this field Is the Kinetic-Molecular Theory.
The kinetic-molecular theory Is based on the assumption that In a hot body, the particles Move faster and thus have More kinetic energy. And Vise-Versa.
The overall energy of motion of The particles that make-up An object is called the Thermal energy of that object. THIS IS DIFFERENT THAN TEMPERATURE!!
What do you use to measure Temperature? Maybe a thermometer?
An Italian physicist invented The very first thermometer, Who was he? Galileo Galilei
Temperature is the “hottness” Of an object as measured Using a specific scale. Heat always flows from hot to cold. A device that measures temperature is called A thermometer.
The choice of a temp. Scale is quite arbitrary. One popular one was invented By Gabriel Fahrenheit.
He devised his own scale. Do you know what it is? Duh, Fahrenheit! His thermometer were popular, So his system was as well.
After a while a different scale Was accepted by Scientists. It was called Celsius, Invented by Anders Celsius
The Celsius scale was the First major scale to Place the freezing point of Water at 0, and the Boiling point at 100.
A few correlations: Melting ice Normal body temp. Boiling water 0°C 32°F 37°C 98.6°F 100°C 212°F
The newest temp. scale Is the Kelvin scale. The Kelvin scale is the SI Scale accepted by scientists It was invented by William Thomson, Lord Kelvin
The difference between the Celsius and Kelvin scales Is very small. It has to deal with the Zero point. 0 Kelvin is the absolute zero, Or °C
At absolute zero, all Kinetic energy stops! Though theoretically possible, It can never be reached, So far.
A few conversions, shall we. °F = 9/5 °C + 32 °C = 5/9 X (°F – 32) K = °C + 273
Let’s try some… 163°C = ? °F 50 K = ? °C -40 °F = ? °C 325°F -223°C -40°C
Convection is the transfer Of heat by means of Motion in a fluid. Radiation is the transfer Of energy by electromagnetic Waves.
Specific heat is the amount of Energy that must be added to a Material to raise the temperature Of a unit mass one Temperature unit. Q = mCΔT Q = heat C = specific heat
A 0.4 kg block of iron is Heated from 295 K to 325 K. How much heat had to be Transferred to the iron? Q = 540 J
Thermal equilibrium is a state Where the rate of energy Transfer between bodies Becomes equal and the bodies Will thus have the same Temperature. Conduction is the transfer of Kinetic energy when Particles collide.
There are 4 states of matter What are they? Solid Liquid Gas Plasma
So how can you go from One state to another? By changing the temperature. Heating or cooling can cause: Boiling, freezing, sublimation, Etc.
The energy required to melt a Substance goes into Rearranging the molecules. The heat of fusion is the energy Per unit mass transferred in Order to change a substance From liquid to solid at a Constant temperature And pressure.
The heat of vaporization is the Energy per unit mass Transferred in order to change From a liquid to a vapor At constant temperature And pressure. Latent heat is the energy per unit Mass that is transferred during A phase change of a substance.
There are formulas to find The amount of heat used By the heats of fusion and Vaporization. Q = mH f Q = mH v
Catherine is asked to melt 0.1 kg of ice at its melting Point and warm the resulting Water to 20.0 °C. How Much heat is needed? Q = 41.8 kJ
First Law of Thermodynamics The energy of the universe is constant. (comes from the law of conservation of energy)
The first law of thermodynamics States that the total increase In thermal energy of a system Is the sum of the heat added To it and the work done on it. Your book says it like this… ΔU = Q - W U = Internal energy Q = Heat W = Work
Q > 0Energy added to system by heat Internal energy increases Q < 0Energy removed from system by heat Internal energy decreases Q = 0No transfer of energy by heat No internal energy change W > 0Work done by system Internal energy decreases W < 0Work done on system Internal energy increases W = 0No work doneNo internal energy change Signs of Q & W for a system
A total of 135 J of work is done on A gaseous refrigerant as it Undergoes compression. If the Internal energy of the gas increases By 114J during the process, what Is the total amount of energy Transferred by heat? Has energy Been added to or removed from The system? Q = -21 J
The second law of thermodynamics States that the entropy of The universe is always Maintained or increased. Entropy is the measure of Disorder of a system.
No machine can be made that Only absorbs energy by heat And then entirely transfers the Energy out of the engine by An equal amount of work. The second law can Also be stated as…
Increasing disorder reduces The energy available for work. Greater disorder means there Is less energy to do work. Entropy can increase or Decrease within a system.
ΔS = QTQT S = Entropy Q = Heat T = Temperature in Kelvins