Energy Flashcards
define work
energy that is transferred when matter is
pushed, pulled or lifted
define energy
the capacity to do work on some form of matter
what forms do energy come in
- potential (gravitation, chemical, nuclear, . . . )
- kinetic (electrical, mechanical, magnetic, . . . )
what is the first law of thermodynamics
Energy is neither created nor destroyed; it is conserved
and can be converted from one form to another.
definition of potential energy
Energy stored in an object that determines how much
work it is capable of doing due to the force of gravity
PE = m × g × h
where m = mass (kg)
g = acceleration due to gravity
h = height above a reference level (m)
definition of kinetic energy
Energy of a moving object
KE = 1/2 x mv^2
molecules that have kinetic energy referred to as …
heat energy
definition of internal energy
Microscopic energy including its translational kineticenergy, vibrational and rotational kinetic energy and potential energy from intermolecular forces
definition of chemical energy
Energy stored in bonds of chemical compounds
eg) batteries and wood store chemical energy
definition of radiant energy
Energy of electromagnetic waves (photons). All matter with a temperature above absolute zero emit radiant energy.
RE = hc/lambda
h = planck’s constant = 6.626 x 10^-34 J s
c= speed of light = 3 x 10^8 ms^-1
lambda = wavelength of electromagnetic wave
definition of temperature
The average kinetic energy of the atoms and molecules in a substance.
definition of heat
Heat is energy in the process of being transferred from one object due to the temperature difference between them.
how is energy stored once heat is transferred from one object to another
it is stored as internal energy
what are the two different forms of heat
- sensible
- heat
definition of sensible heat
energy associated with the kinetic energy of molecules and atoms
definition of latent heat
energy associated with thermodynamic phase changes of a substance
describe latent heat
An important source of
atmospheric energy
* Water vapour evaporated
from Earth’s surface rises to
higher altitudes (i.e.
heights) with colder
temperatures
* Condensation of water
vapour and freezing or
deposition to form ice
release latent heat to the
environment that drives
thunderstorms, hurricanes,
mid-latitude cyclones
what is exothermic
a process that releases energy from the system to the surroundings
freezing, condensation, deposition
what is endothermic
a process that absorbs energy from its surroundings so that heat is transferred to the system
melting, evaporation, sublimation
definition of heat capacity
The heat capacity of a substance is the ratio of the amount of heat energy absorbed by that substance to its corresponding temperature rise
definition of specific heat
the heat capacity of the substance per unit mass, i.e. the amount of heat needed to raise the temperature of one gram of the
substance by one °C.
what are the three main mechanisms heat is transferred by in Earth’s atmosphere
- conduction
- convection
- radiation
definition of conduction
Molecular transfer of heat from warm to cold regions
definition of thermal conductivity
measure of how
efficiently it transfers heat
by molecular motion
eg) air is an extremely poor conductor of air and is therefore used as an insulator
definition of convection
Transfer of heat through a fluid caused by motion
To conceptualize convection, imagine a “parcel” of air —
an invisible balloon-like “blob” of air that can
expand/contract but does not exchange heat with the
environment (adiabatic process) and has the same
pressure as the environment at a given height
The air parcel’s vertical motion is determined by its density,
which is determined by its temperature and water vapour
content
describe adiabatic expansion
As the air parcel lifts,
environmental air pressure
drops
* air parcel uses internal energy
to do work to expand, which
decreases the kinetic energy
of its molecules
* air parcel cools
describe adiabatic compression
As air parcel descends,
environmental air pressure
increases
* environment does work on air
parcel and compresses it,
increasing the kinetic energy
of the molecules and
therefore internal energy of
the parcel
* air parcel heats
definition of advection
The transfer of air properties (temperature, moisture) by wind in the atmosphere.
U · ∇T ,
where U = wind velocity [ms−1],
T = temperature [K]
stronger wind, a larger temperature gradient and/or smaller angle between wind direction and temperature gradient maximize the strength of advection
definition of radiation
Emission of energy in the form of electromagnetic waves or particles through space or material.
- All matter with a temperature above absolute zero
emit electromagnetic radiation - Radiation does not require a medium to propagate,
unlike the transfer of energy via conduction or
convection
properties of waves
wavelength (lambda), speed (v=c), and frequency (f)
c = f λ
on the electromagnetic spectrum, where does the sun radiate?
the sun radiates mostly in the visible spectrum, but also in the UV and near-infrared (IR) part of the electromagnetic spectrum
once the sun’s beam enters the earth’s atmosphere, it …
can be scattered, absorbed or reflected
describe scattering
occurs when sunlight is deflected in all directions upon striking air molecules
when sunlight is scattered by molecules that are smaller in diameter than its wavelength, the molecules scatter shorter wavelengths more effectively - more evenly (Rayleigh scattering)
when sunlight is scattered by molecules that are about the same wavelength as the size of the molecules, the molecules scatter more in the forward direction (Mie Scattering)
why is the sky blue?
The sky is blue because of Rayleigh scattering: small air molecules are more effective at scattering shorter wavelengths (blue colours)
why are clouds white?
Clouds are white because of Mie scattering: large cloud
droplets effectively scatter all wavelengths of visible light
from the sun (which is white) in all directions
why is the sunset red?
Sunsets are red because when the sun sets, the sun is further away from the atmosphere, implying that its beam needs to
travel a greater distance to Earth’s atmosphere, scattering shorter blue wavelengths along the way
definition of albedo
The fraction of incident shortwave radiation that is reflected back to space. the albedo is a measure of how “bright” an object is
what objects have high albedos?
low-level liquid clouds, sea ice or snow-covered surfaces and deserts
on average, what is earth’s albedo?
0.3 - 30%
definition of a blackbody
Any object that is a perfect absorber (i.e. absorbs all the radiation that strikes it) and a perfect emitter (i.e. emits the
maximum radiation possible at its given temperature). the emissivity is the ratio of the energy radiated from a material’s surface to that radiated by a blackbody
what two objects can be treated as blackbodies to good approximation?
the sun and earth
describe Planck’s law
- relates to the distribution of spectral energy emitted by a blackbody as a function of wavelength at a given temperature
- note that blackbodies with higher temperatures emit more radiation at all wavelengths
what is Stefan-Boltzmann law?
The Stefan-Boltzmann law is the statement that the total radiant heat power emitted from a surface is proportional to the fourth power of its absolutetemperature
* It is the integral of the Planck function
F = σT 4
describe Wien’s displacement law
relates the temperature of a blackbody with the wavelength at which it emits the most radiation
it is the peak wavelength of the Planck function
confirms that the sun radiates at shorter wavelengths and the earth radiates at longer wavelengths
what is Kirchoff’s law?
states that good absorbers are good emitters at a particular wavelength, and poor absorbers are poor emitters at the same wavelength. implies that each material has a specific preference for the wavelength it absorbs and emits efficiently
what is the greenhouse effect
greenhouse gases re-emitting infrared radiation back to the surface, warming earth’s surface and lowering the atmosphere
what are the three most abundant greenhouse gases in the atmosphere
- carbon dioxide
- methane
- water vapor
of these three greenhouse gases, methane is the most effective greenhouse gas
how is radiative equilibrium achieved?
when incoming radiation is balanced by outgoing radiation
how does the earth equilibriate radiative forcing?
by transferring heat to the poles
describe arctic amplification
Earth’s arctic is particularly vulnerable to warming — 2-3 times the
pace as the rest of the globe since the 1960s
* Arctic amplification (AA) factor: the number of times the mean
Arctic surface air temperature exceeds that of the globe or
tropics
* Winter and fall phenomenon
* A combination of feedback processes contribute to AA; not only
the sea ice albedo feedback
