Chapter 1 Introduction Flashcards
Thermodynamics can be defined as?
Energy can be viewed as ?
the science of energy
the ability to cause changes
in engineering, we use thermodynamics to
understand how energy is transferred from one form to another in order to accomplish a given purpose
Some applications where thermodynamics is important
Any physical quantity can be characterized
Dimentions
The magnitude assigned to dimensions are called
Units
Basic dimensions
mass
length
time
temperature
secondary dimensions (derived from dimensions ) can be expressed as products of primary dimensions
force
velocity
energy
time
SI prefixed
Some SI and English Units
Work, which is a form of energy transfer, is defined as
force x distance
In SI, work has units of
N*m which is also called a joule
1J=1Nm
in EE, the force unit is the _______, which imparts an acceleration of 1ft/s2 on a mass of 32.174 lbm
in EE, the force unit is the pound-force, which imparts an acceleration of 1ft/s2 on a mass of 32.174 lb
1lbf = 32.174 lbm ft/s2
in the English system, the energy work unit is ______
the ___ is defined as the energy required to raise the temperature of 1 lbm of water at 68 f by 1 f
the unit of time rate of energy, or power is ______
this unit is given the name ______
one foolproof way of converting units is to form_______________ and use them to multiply quantities as necessary
Newtons second law
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
Newton’s second law example
There are three types of systems; the types of systems are differentiated by whether or not mass and/or energy can cross the system boundary:
Isolated System:
Closed System:
Open System:
Isolated System: Neither mass nor energy can cross the system boundary.
Closed System: Energy can cross the system boundary, but mass cannot.
Open System: Both mass and energy can cross the system boundary
When the system undergoes a change in state, it is undergoing a thermodynamic process. Examples of processes include
When the system undergoes a change in state, it is undergoing a thermodynamic process. Examples of processes include
Heating or cooling.
Compressing or expanding.
Changes as electricity flows across the system boundary
A special series of processes is one where, afterward, the system is left at the state where it started.
The series of processes then makes up a thermodynamic cycle.
Devices operating in a cycle can operate indefinitely.
An important example is the cycle utilized in steam power plants, which is called the ___________
Rankine cycle
Rankine cycle
Define equilibrium
Equilibrium is defined as a state of balance due to the canceling of the action of opposing forces.
Mechanical equilibrium
Mechanical equilibrium – there is no change in pressure at any point in the system with time, so there is no fluid motion.
Thermal equilibrium
Thermal equilibrium – the temperature is the same throughout the system, so there is no driver for internal heat transfer.
Phase equilibrium
Phase equilibrium – the mass of each phase present has reached an equilibrium level and stays there.
Chemical equilibrium
Chemical equilibrium – the chemical composition of the system does not change with time.
not as important
A thermodynamic property is a quantity whose?
Examples include
A thermodynamic property is a quantity whose numerical value is independent of how the state of the system was achieved and only depends on the system’s local thermodynamic equilibrium state.
pressure P
temperature T
volume –V
mass m
Properties can be_____ or _______
Properties can be intensive or extensive
Intensive properties are those that are
Intensive properties are those that are independent of the mass of the system, like pressure, temperature, and density
Extensive properties are those whose value depends on
Extensive properties are those whose value depends on the size – or extent – of the system, like volume and mass.
If a uniform system is divided into two equal parts, each part will have the same intensive properties as the original, but its extensive properties will be halved. Intensive properties obtained by taking extensive properties per unit mass are called __________
The properties of a substances are related to each other through equations of state.
Some equations of state are very simple (any often of limited validity), while others are very complicated so that they can represent known property data.
A simple example is the ideal gas law
Isothermal process – a process during which the
Isobaric process – a process during which the
Isochoric process or Isometric process – a process during which the
Isothermal process – a process during which the temperature T remains constant.
Isobaric process – a process during which the pressure P remains constant.
Isochoric process or Isometric process – a process during which the volume –V remains constant.
The Zeroth Law of Thermodynamics
The zeroth law of thermodynamics states that if two bodies are each in thermal equilibrium with some third body, then they are also in equilibrium with each other
A pure substance is a substance that is
A pure substance is a substance that is chemically homogeneous – a substance that has uniform chemical composition throughout.
A phase of matter is a portion of the matter
A phase of matter is a portion of the matter of a pure substance that is physically homogeneous
When multiple phases are present, they are separated by easily ___________________________
When multiple phases are present, they are separated by easily identifiable boundary surfaces.
3 primarily phases
primarily the phases
solid
liquid
gas
Solids phases (there may be multiple solid phases for one substance) have atoms or molecules______ spaced in a fixed lattice structure.
These atoms or molecules are held in place by_________________forces.
A solid maintains its shape without the aid of a container.
As a solid is heated, the molecules will oscillate more and more inside the lattice until they have enough energy to break free.
If these molecules form a liquid, we have _______
If they become vapor, we have _________.
Solids phases (there may be multiple solid phases for one substance) have atoms or molecules closely spaced in a fixed lattice structure.
These atoms or molecules are held in place by intermolecular attractive forces
. A solid maintains its shape without the aid of a container. As a solid is heated, the molecules will oscillate more and more inside the lattice until they have enough energy to break free.
If these molecules form a liquid, we have melting.
If they become vapor, we have sublimation.
Liquid phases (again, there may be multiple liquid phases, liquid helium has two) also have _____________, but they do not maintain a lattice structure.
The molecules can translate and rotate. Intermolecular forces are
________than in solids, but stronger than in gases.
For many liquids, the intermolecular distances increase slightly over the corresponding solid, but in water they ______.
Adding more energy allows the molecules to overcome the intermolecular forces to join the gas phase, and ______occurs.
Liquid phases (again, there may be multiple liquid phases, liquid helium has two) also have closely spaced molecules, but they do not maintain a lattice structure.
The molecules can translate and rotate. Intermolecular forces are weaker than in solids, but stronger than in gases.
For many liquids, the intermolecular distances increase slightly over the corresponding solid, but in water they decrease.
Adding more energy allows the molecules to overcome the intermolecular forces to join the gas phase, and boiling occurs.
Gas molecules move at random, continually colliding with
other molecules and with container walls.
Particularly at low densities, intermolecular forces are very
____________ are the only mode of interaction between
molecules.
Molecules in the gas phase are at considerably higher energy
than those in a _______, so the gas must release a large
amount of its energy before it can condense or ______.
The terms “gas phase” and “vapor phase” both refer to the
same phase, but we typically call gases vapor when the
substance may also be present as liquid or solid (as with
water).
Gas molecules move at random, continually colliding with
other molecules and with container walls.
Particularly at low densities, intermolecular forces are very
small and collisions are the only mode of interaction between
molecules.
Molecules in the gas phase are at considerably higher energy
than those in a liquid or solid, so the gas must release a large
amount of its energy before it can condense or freeze.
The terms “gas phase” and “vapor phase” both refer to the
same phase, but we typically call gases vapor when the
substance may also be present as liquid or solid (as with
water).
phase transitions are the physical processes of transition between ?
phase transitions are the physical processes of transition between a state of a medium, identified by some parameters, and another one, with different values of the parameters.
