Basic Concepts Flashcards
Define a Closed Thermodynamic System
Mass of the substance Stays Constant
Energy is allowed to Cross the Boundary
Define an Open Thermodynamic System
Mass of the substance is allowed to Cross the Boundary
Energy is allowed to Cross the Boundary
Define Thermodynamic System
Define Surroundings
Define Boundary
a substance confined within walls which separate it from the surroundings
Everything External to the System, outside of the Walls
Walls which distinguish the system from the Surroundings
Describe what a property of a System is?
Macroscopic characteristic, to which a numerical Value can be assigned
Mass
Volume
Energy
Pressure
Temperatire
What is the State of a System is ?
The Condition of a system described by numerical values of its properties
Describe what a Thermodynamic Process is?
Transformation of the system from one State to Another
What is an Extensive Property
Depends on the matter within the System .
If you change the mass within the system , this property will change too.
Volume
What is an Intensive Property
Does not depend on the matter within the System.
If you change the mass , this will have no effect on the value of this property
Temperaure, Density
What does Diathermic Mean
Non-Rigid walls that permit the change of state when two closed systems come into thermal contact
Allows the Exchange of Energy
What does Adiabatic Mean
Rigid walls that does not permit the change of state when two closed systems come into thermal contact
Rigid Walls Doesnt allow the exchange of energy
Name the Si Units for the following Properties
Mass
Length
time
force
density
specific Volume
pressure
Mass - kg
Length - m
time - s
force - n
density - kg/m^3
specific Volume m^3/kg
pressure - Pa or N/m^2
Why is specific volume favored over density
Were usually working with gasses with extremely small densities
Specific Volume gives a numerical value easier to work with.
What is Absolute Pressure
What is Guage Pressure
What are Vaccum Pressures
The pressure of a system relative to an Absolute Vaccum
The Pressure of a system relative to atmospheric pressure
pGuage = pAbsolute - pAtmopsheric
The Pressure of a system relative to atmospheric pressure
pVacuum= pAtmopsheric - pAbsolute
Define what Heat is
The energy transferred between two systems in thermal contact due to a difference in temperature
Define Thermal Equilibrium
When the Transfer of Heat between two systems in thermal contact ceases
Temperature is the only determining factor whether two systems are in thermal equilibrium
What does the Temperature tell us about a system
Parameter which tells us the most probable distributions of electrons over the available energy states (Boltzmann distribution)
Temperature Increases, localised electrons migrate to higher energy levels
Infinite temperature, all levels are equally populated
Absolute Zero only the lowest state is populated
The Higher the temperature the larger the kinetic energy
What does Pressure tell us about a system.
Parameter that enables us to predict when the two systems will be in mechanical equilibrium regardless of composition or size
(position of a piston between two chambers)
What is the Zeroth Law of Thermodynamics
A,B,C are 3 separate thermodynamic systems
If A is in thermal equilibrium with B
, and if B is in thermal equilibrium with C
If A and C are brought into Thermal Contact then both will be in thermal equilibrium,
What is the Formula to Convert :
Convert Celcius to Farenheit
Celcius to Kelvin
(1.8 * Celsius) + 32
Celsius + 273.15
Explain Absolute Zero
Pressure of a Gas is proportional to its temperature.
Proportionality Constant is different for Different Gasses
All Gasses reach zero pressure at the same temperature (Absolute Zero)
What is the Formula for the Coefficient of Linear Expansion?
Explain what it is?
Most substances Expand when heated
They Change linear length in direct proportion to the change in temperature
What is the Formula for the Coefficient of Area Expansion?
Explain what it is?
Most substances Expand when heated
They Change linear length in direct proportion to the change in temperature
We derive the change in area by the sum of the linear expansion in the X and Y directions
What is the Formula for the Coefficient of Area Expansion?
Explain what it is?
Most substances Expand when heated
They Change linear length in direct proportion to the change in temperature
We derive the change in Volume by the sum of the linear expansions in the X, Y and Z directions
What is the difference between Conduction, Convection and Radiation
Conduction, Heat transfer between systems that are in direct contact with each other
Convection, Heat transferred between two objects by the fluid movement of the substance
Radiation is the Transmission of Energy By waves or the emission of particles
What is Stored Energy [kJ]
E = U + KE + PE
U = ke + pe , Sum of the kinetic and potential energies of the gas particles at a microscopic level within the system, Depend on the change in gas temperature (different to capital letter version)
KE + PE = Kinetic and Potential Energies of the Whole System at a macroscopic level
E = Stored Energy
Derive how Ke = 0.5mV^2
Derive how Pe = mg*change in height
What is the formula for Heat rate
Define Positive Heat and Negative Heat
Q> 0 , energy is being transferred into the system , due to a difference in temperature
Q<0 , energy is being transferred out of the system , due to a difference in temperature
What are the 4 types of Work?
What is the Formula for Boundary Work
Derive it.
What is the formula for Boundary Work at Constant Pressure?
What does the Pressure of the Gas enclosed by an airtight piston in a cylinder, assume the , due to a difference in temperature Piston is perpendicular to the Ground
Wb = p(V2-V1)
Define Positive Boundary Work and Negative Boundary Work
W>0 , work is done by the system, the system does work on its surroundings as it expands. Energy leaves the system due to heat
W<0 , work is done on he system, work is done on the system as its compressed . Energy enters the system due to Heat
