Academic Team: Physical Quantities

Jerk

1. A non-inertial reference frame is defined as doing this relative to an inertial one. When a particle goes through this, it can create a form of radiation known as brehmsstrahlung. In circular motion, the vector for this quantity is drawn towards the center. The change in this quantity is called jerk, and in Newton's Second Law, it is equal to Force divided by mass. For 10 points, name this quantity, which can be found by dividing velocity by time and is basically speeding up or slowing down. ANSWER: acceleration [or deceleration]

Tension

1. Subtracting the magnetic pressure from this quantity gives the Lorentz force, and Laplace's Law states that pressure is equal to twice this quantity over the radius. In free-body diagrams, it must be represented as a vector pointing away from the object of interest because it can never push, only pull. A two-dimensional form allows small animals to walk on water and is known as the "surface" variety. For 10 points, identify this type of force exerted by taut strings, cables, and cords. ANSWER: tension [accept magnetic tension before "Laplace" is read; prompt on force]

Planck's constant

1. This quantity divides the product of Boltzmann's constant and a term for temperature on one side of the general form of the Eyring equation. The square of elementary charge times c times the magnetic constant, all divided by two times this quantity yields the fine structure constant. A reduced form of this quantity divides it by two pi and is named for Dirac. Dividing this quantity by linear momentum yields a particle's de Broglie wavelength, and the energy of a photon is equal to this constant times frequency. For 10 points, identify this constant which is equal to about 6.626 times 10 to the power of negative 34 Joule-seconds. ANSWER: Planck's constant [prompt on h]

Work, Thermodynamic

10. Although it is not enthalpy, in an adiabatic process, this quantity equals the heat capacity at constant volume times the initial temperature minus the final temperature. For an isothermal process, it equals number of moles times RT times the log of the ratio of the volumes. Carnot efficiency equals this quantity divided by the heat of the hotter reservoir. When applied with a torque, it is called "shaft." This quantity is given by the area inside a cycle on a PV diagram, so its differential equals pressure times the differential of volume. The change in internal energy equals heat minus it, which is positive when done by a system on its surroundings. For 10 points, name this quantity that is the amount of useful mechanical energy derived from a thermodynamic system. ANSWER: thermodynamic work

Velocity

11. Drag force is proportional to both the radius of an object and this quantity by Stokes' Law. Centripetal acceleration equals this quantity squared, divided by the radius of the circle. It can also be found from the first time derivative of (*) position. When the force of gravity is balanced out by drag, a falling object reaches its "terminal" form of this quantity. For 10 points, name this quantity equal to momentum divided by mass, measured in meters per second, that has both magnitude and direction. ANSWER: velocity [prompt on speed before "direction" is read]

Moment of inertia

11. If one knows this value for a principal axis, one can use Steiner's theorem to calculate it for a parallel axis. The discrete form of this quantity is the sum of the product of mass with distance from the principal axis squared. Commonly derived values for this quantity include two-fifths m r-squared for spheres and one-half m r-squared for disks and cylinders. For 10 points, name this rotational analogue of mass. ANSWER: moment of inertia

Speed of light

11. The Lorentz gamma contains the square of this constant in the denominator. This constant is equal to one over the product of the square root of the permittivity and permeability of free space. The square of this quantity serves as the proportionality constant between mass and energy, and special relativity posits it as a universal speed limit. For 10 points, name this constant equal to approximately three times ten to the eight meters per second, symbolized c. ANSWER: speed of light [or c before mentioned] 22. The square of electric charge is divided by the product of h-bar and this quantity in the definition of the fine structure constant. This quantity is equal to the square root of the reciprocal of the product of the permittivity and permeability of free space. The square of this constant is multiplied by (*) mass in an equation developed by Einstein. For 10 points, identify this value symbolized c, equal to about three times ten to the eighth meters per second. ANSWER: speed of light [accept c before mentioned]

Magnetic moment

12. The magnetization of an object is defined by the sum of the average value of this quantity. For 10 points each: [10] Name this quantity defined by the current multiplied by the area vector that dotted with B gives potential energy and crossed with B gives torque. ANSWER: magnetic dipole moment [10] For an atom, the magnetic dipole moment is proportional to the square root of J times J+1, where J is one of these numbers. The principle these include n which gives the energy and l, which gives the angular momentum, and m s, which denotes spin. They correspond to orbitals of atoms. ANSWER: quantum numbers [10] The natural units for expressing an electron's dipole moment is in terms of a magneton named for this Danish physicist. He also names a radius used in his model of the atom that succeeded the Rutherford model but was before the full development of hydrogen. That model gave the correct energies of hydrogen ANSWER: Niels Bohr

Wavelength

13. This quantity is multiplied by an integer value in Bragg's law. According to de Broglie, this quantity is equal to Planck's constant divided by momentum. The inverse of this quantity is known as the wavenumber. A change in this property for light is called a red shift. Additionally, dividing the speed of light by this quantity, denoted lambda, gives the frequency of light. For 10 points, name this property of a wave which for visible light ranges from about 400 to 700 nanometers. ANSWER: wavelength

Solubility

14. A coefficient symbolized alpha and named for Bunsen measures this property for gases. The Hume-Rothery rules determine whether or not two solids mutually have this property. In order for a recrystallization to work, the product should have this property when hot, but not when cold. Liquid-liquid extractions take advantage of the difference in this property between three species. Addition of a common ion will reduce this quantity according to Le Chatelier's principle. On a chart with temperature on the x-axis and this property on the y-axis, solids have a positive slope and gases have a negative slope. Henry's Law gives this property for gases as a function of temperature. For 10 points, name this property measuring how much of a substance can dissolve in another. ANSWER: solubility [accept word forms; or dissolving; prompt on "miscibility" or word forms]

Viscosity

15. Euler's fluid equations assume that this quantity is zero, and the Reynolds number is inversely proportional to this quantity. Its kinematic form is found by dividing its dynamic form by density, and those forms of this quantity are respectively measured in stokes and poise. This quantity is constant for Newtonian fluids, and foods which have a high value for this quantity include mayonnaise and syrup. For 10 points, identify this quantity which measures a fluid's resistance to flow. ANSWER: viscosity

Resistance

2. At low temperatures, phonon scattering causes this quantity to decrease as the fifth power of temperature. An increase in this temperature due to coupling with impurities is the Kondo effect. This quantity is the real part of the impedance. The power dissipated through a wire equals this quantity times the current squared. It is proportional to the ratio of the length of a wire to its cross-sectional area. It is equal to voltage over current by Ohm's Law. For 10 points, name quantity measured in ohms and denoted R. ANSWER: resistance [prompt on R]

Momentum, Linear

2. In quantum mechanics, the operator for this quantity is written as negative i h-bar grad. Although not acceleration, for rigid body motion, Euler's first law can be formulated in terms of this vector quantity. While inelastic collisions do not conserve kinetic energy, they do conserve this quantity. For a force that depends on time, the integral from time one to time two of the force with respect to time gives the change in this quantity, or impulse. For 10 points, identify this quantity equal to mass times velocity. ANSWER: linear momentum [or translational momentum] 3. In quantum mechanics, the Fourier transform of this quantity's operator is represented by the position operator, and this quantity's operator is equal to negative i times h bar times the gradient. Translation invariance of the Hamiltonian or Lagrangian implies conservation of this quantity, which is equal to the product of h bar and the wave number for a photon. It is conserved in both elastic and inelastic collisions, and its change in a given time interval is the impulse. Its time derivative is equal to the product of mass and acceleration by Newton's Second Law. For 10 points, identify this product of mass and velocity. ANSWER: linear momentum [do not accept "angular momentum"] 3. A thought experiment which maps the future of the universe based on the knowledge of this property and location of all particles is known as Laplace's demon. The one dimensional quantum mechanical operator for it is equal to negative i times h bar times the partial derivative of x. The change in this quantity is equal to impulse, and its time derivative is equal to force. For 10 points, identify this vector quantity which is the product of mass and velocity and is often symbolized p. ANSWER: linear momentum [do not accept "angular momentum"]

Stress

20. Cauchy names a tensor of this quantity. The shear form of this quantity is directly proportional to viscosity for Newtonian fluids. The highest this quantity can be without permanently deforming a material is the (*) elastic limit. Often represented with sigma, this quantity is the numerator in the definition of Young's modulus. For 10 points, identify this quantity that, according to Hooke's law, is directly proportional to strain. ANSWER: stress 3. One form of this quantity can be calculated using a Mohr circle. Applying too much of it can cause an object to exceed its yield point. It is found in the numerator of Young's modulus. The definition of Le Chatelier's principle states that a system counteracts the effects of an applied one of these. Like pressure, this quantity is measured in pascals and equals the applied force over an area, resulting in a strain. For 10 points, name this term describing a physical or emotional tension. ANSWER: stress

Frequency

20. For an undulator, the most prominent value for this quantity is proportional to the Lorentz gamma squared over the sum one plus the product of the Lorentz gamma squared and the angle squared. For alternating current in a conductor, the skin depth is given by the square root of the quantity two over the product of permeability, conductivity, and this quantity. The levels of the quantum harmonic oscillator are quantized in discrete units of this quantity. The energy of a photon is given by Planck's constant times this quantity, and for a pendulum, this quantity is given by the square root of the gravitational acceleration over the length. For ten points, identify this quantity in physics which is the inverse of the period and has units of inverse seconds, or hertz. ANSWER: frequency [10] This value for a simple harmonic oscillator is proportional to the square root of stiffness over mass. The maximum velocity of a simple harmonic oscillator is proportional to this quantity and amplitude. ANSWER: frequency [prompt on f]

Helmholtz free energy

21. Entropy is the negative derivative of this type of free energy with respect to temperature at constant volume and particle number. For 10 points each: [10] Name this quantity that is also the difference of internal energy and temperature times entropy. ANSWER: Helmholtz free energy [prompt on "free energy"] [10] This function, symbolized Z, is the sum over all states of their corresponding Boltzmann factors. ANSWER: partition function [10] This is a statistical ensemble such that all systems in the ensemble are at the same energy so the systems are isolated. ANSWER: microcanonical ensemble

Power, Electrical

23. The points named for half of this value on a transfer function plot are alternately called the 3 dB points. The cosine of the phase angle is equal to this value's namesake factor. A time-averaged form of this quantity's density divided by the speed of light gives the radiation pressure. This quantity is equal to the surface integral of the cross product of the electric and magnetic fields according to Poynting's theorem. The maximum amount of this quantity is transferred when the load resistance is the same as the Thevenin resistance. Using Ohm's law, it is found to be current squared times resistance for a resistor. For ohmic elements, it is often given off as heat. For 10 points, name this quantity that is the amount of energy a circuit transfers per unit time and is measured in watts. ANSWER: electrical power

Equilibrium constant

3. Pure species are ignored during the computation of this value because they have no activity. The change in Gibbs free energy is equal to negative RT times the natural log of this value. Comparing this value to the reaction quotient is used to apply Le Chatlier's law, and this quantity is usually calculated as products over reactants. For 10 points, name this quantity used to characterize reactions in which the forward and reverse rates are equal, usually symbolized K. ANSWER: equilibrium constant [or mass action constant; accept K before it is read; accept reaction quotient or Q before it is read]

Force

3B. What quantity from physics is equal to the product of mass and acceleration? ANSWER: force [prompt on F]

Wavefunction

4. In the particle-in-a-box model, this quantity is equal to the sum of A sin k x plus B cos k x quantity times e to the i omega t, and for the hydrogen atom model this quantity contains the product of a spherical harmonic and a Laguerre polynomial. The norm of these quantities is necessarily equal to 1, and the square of the magnitude of this quantity at any given state is the probability of the system existing at that state. In one interpretation, observation of a system causes the eigenstates of this value to be replaced by a single eigenstate. The Hamiltonian operator of this quantity is equal to the total energy of the system times this quantity; that equation is named for Schrodinger. For 10 points, name this quantity symbolized psi and used to describe the state of a quantum mechanical system. ANSWER: wavefunction

Mass

5. A "reduced" form of this quantity is used in solving the two-body problem, and a change in this quantity for problems involving atomic nuclei is known as its namesake "defect" or "deficit." For a rigid body with uniform density, the centroid is the location of the "center" of this quantity, and adding the prefix "bio" to this word gives a term for biological material from organisms. Dividing this quantity by volume gives density. For 10 points, identify this quantity measured in kilograms. ANSWER: mass [prompt on m]

Magnification

5. Dividing the diopter of a lens by four and adding one is a simple way to calculate this quantity. When prefixed by "bio," this term can refer to the increase in concentration of toxic chemicals as one progresses up the food chain, such as DDT in bald eagles. For a single lens, this quantity can be calculated as the focal length divided by the quantity focal length minus object distance. For 10 points, identify this term which refers the ratio of image size to object size, which colloquially refers to the amount of enlargement of an image. ANSWER: magnification [accept word forms such as magnifying]

Speed of sound

5. In a system of small volume, this quantity can be calculated using Kundt's tube, and one person to attempt to calculate this quantity was William Derham. The Newton- Laplace equation states that this quantity equals the square root of bulk modulus over density, and another formula states that, in air, it can be calculated as 0.606 times the temperature plus 331.3. It is equal to about 768 miles per hour, or 343 meters per second. For 10 points, identify this quantity which is equal to Mach 1. ANSWER: speed of sound [accept early buzz of Mach 1]

Torque

6. In electric fields, this quantity is the cross product of the electric dipole moment and the field. In gyroscopes, this quantity produces a change in "L" that causes precession. For an orbiting body, this vector quantity always points perpendicular to the plane of the orbit. This quantity is equal to the time derivative of angular momentum. For 10 points, name this cross product of force and displacement, the angular analogue of force. ANSWER: torque

Euler's number

6. This number can be approximated by the infinite series quantity one plus quantity one over n end quantities, all raised to the n. The Taylor series of this number raised to the power of x is the sum from n equals zero to infinity of x to the n divided by n factorial. When raised to the power of x, it is also equal to its own derivative. This number is the base of the natural logarithm. For 10 points, identify this number whose symbol derives from the name of the first person to calculate it, Euler. ANSWER: e [or Euler's number before it is read]

Temperature

6. This quantity can assume a negative value after population inversion. The mnemonic "oh be a fine girl kiss me" places stars in decreasing values for this quantity, which is plotted with color against absolute magnitude in a Hertzsprung-Russell diagram. This quantity is directly related to the kinetic energy of particles and can be found by dividing PV by nR when rearranging the ideal gas law. The Kelvin scale for this quantity is based on the concept of absolute zero, its lowest attainable value. For 10 points, name this quantity measured in Celsius. ANSWER: temperature [prompt on T] 1. This quantity is the conjugate variable of entropy. The energy radiated by a blackbody is proportional to the fourth power of this quantity. Subtracting the product of this value with the change in entropy from the change in enthalpy gives the Gibbs free energy. This measure roughly quantifies the average kinetic energy of a gas. One mole of a gas occupies 22.4 liters at the standard value for this quantity and pressure. For 10 points, name this quantity whose "absolute" type is kelvins. ANSWER: temperature [or T]

Momentum, Angular

7. The operator for this quantity is equal to negative i times h-bar times quantity r cross grad. This quantity is equal to the time derivative of the torque. Kepler's equal area law can be derived from the conservation of this quantity, which is also responsible for the fact that a skater spins faster when they pull their arms in. This quantity is equal to the moment of inertia times the angular velocity. For 10 points, name this quantity symbolized L, which is a rotational analogue the product of mass and velocity. ANSWER: angular momentum [prompt on momentum; do not accept "linear momentum"]

Zero-Point Energy

8. This quantity's spectrum depends on frequency cubed, allowing it to be Lorentz invariant. For 10 points each: [10] Name this quantity, the ground-state energy of a quantum mechanical system. It equals h times frequency over two for the quantum harmonic oscillator, and mathematically results from the uncertainty principle. ANSWER: zero-point energy [10] The zero-point energy density of the universe is analogous to this constant symbolized with a capital lambda, which Einstein called his "biggest blunder" when he included it in his field equations. ANSWER: cosmological constant [10] The ratio of pressure to energy density for an exact cosmological constant would be equal to this number, suggesting that the universe is expanding. ANSWER: negative one

Distance

8A. In astronomy, standard candles are used to find what quantity that is measured in light years?

Work

9. The principle of least action can be rewritten as the principle of the virtual form of this quantity. The magnetic force on a charged particle cannot contributes 0 of this quantity because velocity is crossed with the magnetic field. It is equal to the line integral of a particle's path through a vector field. The change in this quantity divided by the time elapsed gives (*) power. This quantity is equal to the change in kinetic energy. For 10 points, identify this quantity equal to force times distance and measured in joules. ANSWER: work

pH

9B. What useful value in chemistry is defined as the negative logarithmic value of the concentration of hydrogen ions? ANSWER: pH 9B. What measurement of the acidity of a substance is measured with indicators like methyl red? ANSWER: pH

Electronegativity

A common scale for measuring it is named for Linus Pauling. For 10 points each: [10] Name this property, which quantifies the ability of an atom in a compound to attract electrons to itself.

Surface Area

According to the mass continuity equations for a fluid, given two points in a fluid, the product of density, fluid velocity, and this quantity at those points will be equal. Fourier's law of conduction states that the change in big Q with time is negatively proportional to the product of this quantity and the derivative of temperature with position. The Stefan- Boltzmann constant has units of power divided by the product of the fourth power of temperature and a measure of this quantity. Teslas are equivalent to one weber per this measure and is thus used to measure magnetic flux density. Kepler's second law states that orbits sweep out equal this in equal time. For 10 points, name this quantity which can be reported in square meters.

Boiling point

An azeotrope either minimizes or maximizes this quantity depending on whether the solution shows positive or negative deviations from Raoult's Law. Compared to a pure solvent, a solution will increase this quantity proportionally to its molality. Liquids for which this quantity is lower than the external temperature are called volatile. It is defined as the temperature at which the external pressure and the vapor pressure of a liquid are equal. For 10 points, name this point, which at one atmosphere of pressure is one hundred degrees Celsius for water.

Amplitude

Answer some questions about simple harmonic oscillators. For 10 points each: [10] For a simple harmonic oscillator, the maximum displacement, or greatest distance from the equilibrium point, is this quantity. It is symbolized A.

Entropy

At constant temperature, the change in this quantity equal n times R times the natural logarithm of the ratio of volumes. It can be written as the sum of the probabilities of the microstates multiplied by Boltzmann's constant. It is linked to Q over T in several theorems. This quantity approaches zero as the temperature approaches absolute zero according to the Third Law of Thermodynamics. Enthalpy minus this quantity times the change in temperature equals the change in Gibbs free energy. For 10 points, name this quantity symbolized S, a measure of disorder in a system.

Charge (Addressing Coulomb's Law)

Couloumb's law contains two terms for this quantity, symbolized q. For an electron, it is about negative 1.6 times ten to the negative nineteen coulombs. In the denominator of the expression for Coulomb's law, the distance between the charges is raised to this positive integer power. ANSWER: two The Coulomb constant, k, can be rewritten as one over this integer times pi times permittivity of free space. ANSWER: four

Electromotive Force

For a closed loop, this quantity can be found by taking the line integral of the Lorentz force per unit charge. For an electrochemical cell, this quantity is equal to the negative change in Gibbs free energy over number of moles of electrons times Faraday's constant. This quantity is generated when two dissimilar metals are joined together in the Seebeck effect. For a wound coil of wire, this quantity is equal to the number of coils times the time derivative of magnetic flux in a single coil by Faraday's law of induction. For 10 points, name this quantity usually denoted with a script "e" that is defined as the work per unit charge required to produce an electric potential difference. ANSWER: emf [or electromotive force; or voltage]

Vector magnitude

For a vector, what value can be found by taking the square root of its dot product with itself or the square root of the sum of the squares of the components? ANSWER: magnitude

Entropy

For one type of object, this quantity is proportional to the cube of the speed of light and one-fourth the area of the object. For an ideal gas, this property approaches negative infinity as temperature approaches absolute zero, as a consequence of the natural logarithm term in the Sackur-Tetrode equation. In information theory, it is proportional to the sum over all possible values of a random variable of the quantity p sub i times natural log of p sub i. That relation is derived from a similar equation, stating it is proportional to the natural log of the number of microstates of a system, elucidated by Ludwig Boltzmann. For 10 points, name this ever-increasing quantity that measures the amount of disorder in a system.

Electric Field

In electrostatics, this quantity has a non-zero curl. For 10 points each: Name this quantity whose curl is proportional to the negative change in magnetic flux. Symbolized E, multiplying it by charge gives force in Coulomb's law.

Enthalpy

It equals the internal energy plus the product of pressure and volume of a system. For 10 points each: [10] Name this quantity that represents the thermodynamic potential of a system.

Electronegativity

One method of calculating this quantity uses the square root of the differences of dissociation energies of certain bonds between two elements. The partial ionic character of a bond is determined by the difference of this value for the two elements involved in the bond. This quantity is measured on the Pauling scale, and fluorine has the highest value of it. For 10 points, name this quantity, the ability of a bonded atom to attract shared electrons in a bond.

Energy, Potential

One type of this quantity is calculated as the negative dot product of the magnetic dipole moment and magnetic field. In a two-body system, this quantity is proportional to the product of the two masses divided by radius. For a spring, this quantity is equal to one half times the spring constant times displacement squared. The (*) gravitational form of this quantity is equal to a constant times mass times height. For 10 points, name this type of energy arising from the configuration of a system which is contrasted with kinetic.

Enthalpy

Processes that leave this quantity constant include throttling. The process of breaking a chemical bond always has a positive value of this quantity. Hess' law can be used to calculate the change in this quantity for a multi-step process. This quantity is defined as a system's internal energy plus the product of its pressure and its change in volume. The change in this value is always negative for exothermic processes and positive for endothermic ones. For 15 points, name this thermodynamic variable, the change [of] which is symbolized as delta H.

Charge on the Electron

Robert Millikan earned a doctorate at Columbia before measuring this fundamental physical value with the oil drop experiment.

Electron Capture

The atomic number is decreased by one, but the mass number is unchanged, in this process that is regarded as "inverse beta decay."

Bound (Electric Displacement Field)

The electric displacement field takes into account these sorts of charges in a material. These sorts of states generally occur when the energy of a system is negative, and polarization of a material rearranges these charges.

Angle

The magic type of this quantity helps reduce line broadening and dipole interactions in NMR spectroscopy. Phi and psi are letters used to denote one type of these in amino acids, and they are plotted on the Ramachandran plot. One named after Brewster is involved in polarization. Formed by two rays with a common vertex, the one associated with incidence is equal to the one associated with reflection. For 10 points, identify these entities which can be acute, obtuse, or right.

Neutron

The mass number is determined by the combined number of protons and of this neutral particle in the nucleus.

Entropy

The probability the time-averaged value for this property takes a given value over the probability it takes the opposite value follows an exponential function, as shown in the fluctuation theorem. The H-theorem shows the change of this property in an ideal gas is irreversible. The H-theorem was developed by the same man who defined this property as the logarithm of available microstate times Boltzmann's constant. Clausius defined it as the line integral of change in heat over temperature. The second law of thermodynamics states this value must universally be increasing. For 10 points, name this measure of a system's disorder.

Legendre transformation

The thermodynamic potentials are all related to each other by this transform that also changes the Lagrangian into the Hamiltonian. It changes the variable in a function

thermodynamic potential functions

These functions include internal energy, and the Gibbs free energy. For 10 points each: Name these functions in thermodynamics that are named similarly to energy that is defined as the capacity to do work.

Entropy Facts

This concept was introduced by Rudolf Clausius, who noted that its change was equal to the change in heat divided by the temperature. For 10 points each: Name this thermodynamic quantity related to the amount of disorder in a system. ANSWER: entropy Entropy always increases in a spontaneous reaction according to this law. ANSWER: second law of thermodynamics Clausius was studying this theoretical process, which consists of two isothermal steps and two reversible adiabatic steps. ANSWER: Carnot cycle

Atomic number

This number is denoted Z. Name this number, which for an atom is given by the number of protons in the nucleus. ANSWER: atomic number

Gibbs Free Energy

This quantity is defined as enthalpy minus the product of entropy and temperature in Kelvin. It describes the amount of energy available to do work.

Electric Displacement Field

This quantity is defined as the vacuum permittivity multiplied by the electric field plus the polarization density. It is useful for calculating the electric fields in dielectric materials. Unlike electric field it has a non-zero curl. A similarly named current was added by Maxwell to fix Ampere's law.

Enthalpy

This quantity is plotted on the Y axis against entropy in a diagram used to find the "dryness fraction", the Mollier diagram. The Joule-Thompson process keeps this quantity constant. The change in this quantity can be calculated through the Born-Haber cycle using Hess' law. This quantity minus temperature times entropy gives the Gibbs free energy. For 10 points, name this quantity whose change is used to characterize whether a reaction is endo- or exothermic, usually symbolized H.

Enthalpy

This quantity remains unchanged in the throttling process, as well as in an adiabatic process that is irreversible and does no work. This state variable's total for a given reaction is independent of the number of steps involved according to (*) Hess's law. This quantity is equal to internal energy plus pressure times volume. Its change is negative for exothermic reactions. For 10 points, name this quantity whose change, in a system at constant pressure, is equal to the heat absorbed or released.

Enthalpy

This thermodynamic potential is equal to the internal energy plus the product of volume and pressure. For constant pressure systems, the change in this equals the heat transferred.

Enthalpy

With kinetic energy, this quantity is unchanged in a Joule-Thompson process. One form of this quantity, that describes the binding in an ionic solid, is calculated using a Born-Haber cycle and is the lattice variant. It is equal to internal energy plus pressure times volume. The Gibbs free energy of a system is defined as this quantity minus temperature times entropy. For 10 points, name this quantity symbolized H, that represents the total energy of a system under constant pressure.