Chapter 4 Flashcards
Work, Energy & Power
Forces can be used to do
Work
Force does work when it
Acts on an object & displaces the object in the direction of the force
What is the equation for work?
W=F (magnitude of force) x d (magnitude of displacement) x cos
(W=F x d)
If there is no force, then
No work is being done
If the magnitude of the force is 0, then
No work is done
Magnitude of the force is
Constant over the displacement
1 joule of work is expended when
A force of 1 N acts over displacement of 1L
Unit of work is
Joule
Work & kinetic energy have units of
Joule
Joule is the combination of
Newton & Meter
Once joule of work is expended when
A force of 1 N acts over a displacement of 1m
Kinetic energy is also called
Energy of motion
Kinetic energy is the
Energy a mass has by virtue of being in motion
What is the work-energy/work-kinetic energy theorem?
The total work done on a system is equal to the system’s change in kinetic energy
Gases that move can
Also do work & breathing is a moving gas
State functions are mathematical functions that describe the
“State” of a system & can be described as using volume, pressure, or temperature
State functions are
Independent of the path by which a system gets to a particular state
An example of a state function is
Internal energy, U
What is not a state function?
Work
Work depends on
The path one takes in getting from the starting point to the end point
Work done by the gas is
Path dependent (depends on how you change the state parameters [volume, pressure &/or temp)
What is isochoric?
Constant volume
What is isobaric?
Constant pressure
The amount of work in a given process is highly dependent on
How the pressure & volume change
For changing volume &/or pressure of a gas, the
Work is equal to the area under the curve describing the process
The slower the change in volume,
The closer the approximation
Energy is defined as
The capacity to do work
What is the Law of Energy Conservation?
The amount of energy int he universe is constant & is constantly being converted from one form to another
Energy is neither created nor destroyed, but only converted to other kinds of energy
Unit for energy?
Joules
One calorie (thermochemical calorie) is
Exactly 4.184 J
The food Calorie (capital C) is a
Kilocalorie or 1,000cal
The Calorie is an
Immense amount of energy
What is potential energy?
Energy that is stored bu virtue of position
What is conservative force?
Forces that perform no work around a closed path
What can change the potential energy of a system?
Only conservative forces
Potential energy can be
Recovered & used later
Potential energy is sometimes called
Stored energy
What examples of potential energy?
Airplane in the air
Battery
Chemical energy in food (sugar, fat)
Thermal energy
Light
Potential energy is the property of a
System & not of an isolated object
All energy quantities are
Scalar
What is the internal energy?
The sum of all the kinetic & potential energies of a system
Results from the state of the particles at a molecular level
What is thermodynamics?
The study of energy
How energy is interconverted from one form to another
How energy flows into & out of thermodynamic systems
Everything near a system is called
Surroundings
What is the Zeroth Law of thermodynamics?
What is the First Law of Thermodynamics?
The change in the internal energy of a system is equal to the sum of the heat processed that cause energy to flow into/out of the system & the work done by/on the system
Q>0–>
Endothermic process: energy flows into the system
Q<0–>
Exothermic process:energy flows out of the system
W<0–>
Work done by the system on the surroundings-expansion
W>0–>
Work done on the system by the surroundings-Compression
The Second law is sometimes called
Entropy Law
Entropy is a measure of
Randomness or disorder in a system
Systems that have more randomized, chaotic or evenly mixed have
More entrpy
The Second Law states
Entropy of the universe is constantly increasing
The universe NEVER & a system almost never spontaneously become more organized
It is not possible to lower a temperature
To absolute zero
Heat is energy that is transferred as a result of
A temperature difference
(energy flow/process)
Temperature of an ideal gas is
Proportional to the average kinetic energy of the particles in a sample of the gas
For a given sample of a single type of gas molecule
Not all of the molecules will have the same speed or kinetic energy
(will exhibit a distribution of speeds & kinetic energies)
Distribution is
Temperature dependent & is called the Maxwell speed distribution
The internal energy of an ideal gas is directly
Related to the random, disordered motion of the gaseous molecules or atoms
What is integer?
Find the area under the curve
The temperature of the sample depends on the
Average kinetic energy
Heat capacity is defined as the
Ratio between the amount of heat added to or taken away from an object & the change in temperature of the object
Unit of heat capacity
J/K
Heat capacity is an extensive property of
Matter
Larger samples have greater
Heat capacities
The heat capacity of a given object depends not only on the mass of that object, but also on the
Type of material contained in the object
(specific heat, c)
Specific heat & heat capacity are almost always
Positive quantities
Whenever a quantity is divided by a mass, the term
Specific is placed in front of the name of the quantity
Water has a large
Specific heat; much energy will flow into water
Materials with large specific heat are good
Thermal insulators
Good thermal conductors have low
Specific heats
What is power
The rate of doing work or the rate of expending energy
Unit for power
watt (W), which is defined as joules/second
(capital W)
Gas solubility in liquids is inversely related to
Temperature
As temperature increases, less
Gas is able to dissolve into a liquid
An increase in temperature represents
Greater kinetic energy
Greater kinetic energy allows
Dissolved gas molecules to escape & prevents further dissolving
Lower temperature slows the kinetic energy of gas molecules, allowing
Them to dissolve into liquids
The hypothermic patient
Retains anesthetic gases in the blood because of increased solubility related to temperature
Gas solubility in a liquid is directly proportional to
Pressure & is described by Henry’s law
The entropy of an isolated system not in equilibrium will
Increase over time, approaching a maximum value at equilibrium
Energy can be expressed as
Mechanical work
Chemical Reactions
Heat
Entropy is the universal trend towards
Equilibration
Entropy is unidirectional & is the movement of energy from a
Higher concentration to a lower
The greater the gradient difference, the greater the
Flow
When does Entropy end?
When all energy is equally distributed
Temperature is the measurement of the
Thermal state of an object
Heat is thermal energy; temperature is the
Quantitative measurement
Molecules in a solid state are held together by
Intermolecular forces & move about slightly & vibrate
Molecules in a liquid are held together by
Intermolecular forces & may slide or floe by each other
Molecules in a gas move linearly & the attractive forces between molecules are
Less than their kinetic energy. They move free from on another
Molecules have no
Volume
Gas molecules exert no force unless they
Collide
Collision of molecules with each other or the walls of the system do not
Decrease the energy of the system
Molecules of a gas are in
Constant & random motion
The temperature of a gas depends on its
Average kinetic energy. The energy of a gas is entirely kinetic
Temperature & volume in Charles Law, when pressure is the constant is
Directly proportional
Pressure & volume in Boyle’s law, when temperature is a constant is
Inversely proportional
Pressure & temperature in Gay-Lussac’s law, when volume is the constant, is
Directly proportional
Compressing a gas quickly will
Intensify the kinetic energy
Temperature will quickly rise proportional to the decrease in volume
1N equals
9.8=1kg
Work is the product of
Forces & displacement
Kinetic Energy equation
KE=1/2mv(squared)
What is the work energy theorem
Change in the quantity of kinetic energy
Work equals
pressure x change in volume
What is a state function
A property whose value does not depend on the path taken to reach the value
State functions only depend on
Current equilibrium
What are path functions?
Heat
Work
The amount of work depends on
The pathway
What is energy?
The capacity to do work or the exertion of force (PE vs KE)
What is the Law of conservation Energy?
Energy can neither be created nor destroyed; can only be changed from one form to another
the calorie is how many Joules?
4.184J
PE equation
PE=mass x gravity x height
Potential energy is _______ energy
Stored
Kinetic energy equation
KE=1/2mv (squared)
What is internal energy?
Movement of molecules within the system (sum of PE & KE)
A substance doesn’t contain heat, but
Energy
Thermodynamics is the study of
Energy & how it is converted from one form to another & flows into & out of a system
What is Zeroeth Law?
2 systems in equilibrium with a 3rd system are in thermal equilibration with each other; If A=B & B=C, then A=C
First law of Thermodynamics?
Energy neither created nor destroyed; change U=Q-W (change in internal energy=energy supplied to system minus amount of thermodynamic work done by the system)
Second law of Thermodynamics
Entropy always increases
Third law of Thermodynamics
Entropy of a system approaches a constant as temperature approaches absolute zero
Entropy is
Equilibration of energy; universal trend to equilibration; unit directional; movement of energy from high to low
Temperature is the measurement of a
Thermal state of an object; numerical ranking & quantitative
heat is thermal energy & is
Energy that is transferred as a result of temperature differences
Internal energy of an ideal gas is
Directly related to random disordered motion of the gaseous molecule or atoms
The greatest change in temperature occurs
After the first hour an anesthetic has been given
Liquid to gas requires
Energy
2500J/600calories is requires to
Convert 1g of water into vapor
What is the latent key of vaporization?
The energy needed to transform a given amount of liquid into a gas & is measured in kilo-joules
What is boiling?
The temperature where bulk of the liquid at a given pressure concerts to a vapor
Temperature of a liquid will
NOT rise above its boiling point; the additional heat is transformed liquid into a gas
The rate of vaporization depends on the
Temperature of the vapor pressure of the liquid & the partial pressure of the liquid above the liquid
Vapor pressure & boiling points are
Inversely related; the lower the boiling point, the higher the vapor pressure
What is relative humidity
The amount of water vapor in the air compared to the maximum water vapor the air can hold at that temperature
What is specific heat
The heat required to raise the temperature of a mass of a given substance by giving temperature 1 degree
The Kinetic Molecular Theory focuses on
Molecular movement & the forces between molecules
Ideal gas law does not
Take into account the small volume of gas molecules & their intermolecular interactions
Power is the
Rate of doing work or rate of expended energy; amount of work to be done in a given amount of time
Power formula triangle
W with P across from T
