Thermodynamics and Quantum Concepts of Light and Matter

Vocabulary flashcards covering core thermodynamics concepts, enthalpy, Hess's Law, and the wave-particle duality of light and matter.

Energy

The capacity to do work or transfer heat.

Potential energy

The energy an object possesses as a result of its position with respect to another object.

Kinetic energy

The energy that an object possesses by virtue of its motion, which is one of the two fundamental forms of energy along with potential energy.

Heat capacity

The amount of heat required to raise the temperature of an object by $1\,\text{K}$.

State function

A property of a system that depends only on its current state (conditions), not on how it got there, such as $P$, $V$, $T$, $E$, and $H$.

Exothermic

A process in which the system loses heat and heat flows out into the surroundings.

Endothermic

A process in which the system absorbs heat from the surroundings.

Change in enthalpy ($\Delta H$)

The heat gained or lost by a system in a process occurring at constant pressure, calculated as $\Delta H_{rxn} = H(\text{products}) - H(\text{reactants})$.

Hess’s Law

A law stating that if a reaction is carried out in a series of steps, the overall enthalpy change ($\Delta H$) equals the sum of the $\Delta H$ values for each step.

Electromagnetic wave model for light

A model in which light is a wave of oscillating electric and magnetic fields that carries energy through space.

Photon

A single "packet" (quantum) of light energy. In quantum theory, each photon carries energy given by $E = h\nu$, where $E$ is energy, $h$ is Planck’s constant, and $\nu$ is frequency.

Wave-particle duality of light

The property of light showing both wave-like and particle-like behavior depending on the situation: as electromagnetic radiation with oscillating electric and magnetic fields described by wavelength and frequency, and as particles consisting of photons with $E = h\nu$.

Wave-particle duality of matter

The property that matter can behave as both a particle and a wave, where de Broglie proposed that any particle with mass $m$ and velocity $v$ has a wavelength related to Planck’s constant $h$ and momentum $mv$.

Matter waves

The waves associated with particles possessing mass $m$ and velocity $v$, where $h$ is Planck’s constant and $mv$ is the particle’s momentum.

λ

(Greek lambda) Wavelength -- m or nm

ν

(Greek nu) Frequency -- s⁻¹ or Hz

Å

Angstrom -- 100pm

c

Speed of light, 3.0010⁸ m/s

E

Energy of 1 photon -- J

h

Planck's constant, 6.62610⁻³⁴ Js ==>

N_A

Avogadro's constant, 6.02210²³ mol⁻¹

R

Rydberg constant, 1.09710⁻² nm⁻¹ or 2.1810⁻¹⁸J

1eV= 1.60210⁻¹⁹J

λ= ν/f

general wave equation or =>

c= λν

convert between wavelength and frequency

E= hν

Photon energy increases with frequency

E= hc/λ

Photon energy increases as wavelength decreases

λ= h/mv(velocity)

De Broglie Wavelength Equation

E_mol= hc/λ N_A

energy per mole of photons

2.1810⁻¹⁸J(R)(1/n₂² - 1/n₁²)

Energy per photon.

1/λ= 1.09710⁷m⁻¹ (or 10⁻² nm⁻¹) (R)(1/n₁² - 1/n₂²)

Skip energy for Wavelength

Gamma Rays

X-rays

0.01nm - 10nm

Ultraviolet

10nm - 400nm

Visible light

400nm(violet) - 700nm(red)

Infrared

700nm - 1mm

Microwaves

1mm - 1m

Radio waves

1m - 100km