Chapter 2 self study Flashcards
What is energy ?
the ability or capacity to do work on some form of matter
What is potential energy?
is the stored energy in a mass that has the potential to do work
PE = mgh where
m → mass
g → gravity (9.8 m/sec2)
h → height above ground
Think of a lake behind a dam.(Gravitational PE)
The burning of fossil fuels (coal, petroleum)
The consumption of food(Chemical PE)
What is Kinetic Energy?
KE = ½mv2
m → mass
v → velocity
Kinetic energy is the energy of motion
Any moving object possesses kinetic energy
The faster an object moves, the greater the kinetic energy
If same speed, the object with greatest mass would have more kinetic energy
Heat energy → molecular motion
Radiant energy → that received from the sun
First Law of Thermodynamics
This is the law of conservation of energy.
The total amount of energy in the universe remains constant.
Energy cannot be created nor can it be destroyed.
What is temperature a measure of ?
The temperature is a measure of a substance’s average kinetic energy
or
temperature is a measure of the average speed of the atoms and molecules (molecular motion).
Warm air → molecules farther apart/volume
Less dense
Cold air → molecules closer together/volume
More dense
What are the 3 transfers of heat ?
Conduction, convection and radiation
What is heat?
Heat is energy in the process of being transferred from one object to another because of the temperature difference between the two objects (warm → cold).
After heat is transferred where is it stored?
Internal energy
What is the absolute zero temperature?
-273C(-459F)
Specific Heat
The heat capacity of a substance per unit mass.
Scientifically, specific heat is the amount of heat (energy) needed to raise the temperature of 1 gram of substance 1˚C.
Latent Heat
Latent heat is the heat energy required to change a substance from one state (phase) to another.
water vapor ↔ liquid water
liquid water↔ ice
water vapor ↔ ice
Freezing (Latent Heat Number)
+80cal/gr
+ heat energy added to the environment
Evaporation
is a cooling process
Energy is lost when faster moving molecules escape, this brings down the average molecular motion of the water droplet
The water droplets will cool along with the surrounding air
Condensation
is a warming process
The lost energy (hidden) is released when the water vapor condenses back to a liquid
This released energy will warm the air around the newly formed water droplets
Conduction
The transfer of heat from molecule to molecule within a substance.
Heat flows from warmer to colder regions
Generally, the greater the temperature difference, the more rapid the heat transfer
Metals are good heat conductors because their molecules are structurally bonded together.
Air is an extremely poor conductor of heat
What provides a tremendous amount of energy for storms such as hurricanes, mid-latitude cyclones and thunderstorms?
Latent Heat
Convection
Convection → The transfer of heat by the mass movement of a fluid (water & air)
Water & air can move freely allowing currents to set up within them
Convection happens naturally in the atmosphere
Vertical motion is “convection”
Horizontal motion is “advection”
Thermal
is a rising bubble of air that carries
heat energy upward by convection
Radiation (Radiant Energy)
Energy received from the sun and all things whose temperature is above absolute zero.
Radiation travels in the form of waves that release energy when they are absorbed by an object.
Because these waves have magnetic and electrical properties, they are called “electromagnetic waves”
Longer waves carry less energy than shorter waves
Electromagnetic Waves
They do not need molecules to propagate (can travel through a vacuum → space)
In a vacuum they travel at a constant speed (the speed of light → ≈186,000 miles/sec
Wavelength (λ)
The distance measured along a wave from one crest to another.
Micrometer (μm)
Equal to one-millionth of a meter (m) or 10-6m
Stefan – Boltzmann Law
As the temp of an object increases, more total radiation is emitted each second.
E = σT4
E → max rate of radiation emitted by each m2 of surface area in Watts (W)
σ → (sigma) Stefan – Boltzmann constant 5.67×10-8 W/m2K4
T → objects surface temperature in Kelvin
The Balancing Act
Absorption, Emission & Equilibrium
All objects not only radiate (emit) energy but they absorb it as well.
Objects that emit more energy than they absorb get colder
Objects that absorb more energy than they emit get warmer
Objects that emit and absorb energy at equal rates hold a constant temperature (Radiative Equilibrium)
Absorption Characteristics
The rate at which something radiates and absorbs energy depends strongly on its surface characteristics:
Color
Texture
Moisture content
Temperature
Atmospheric Absorption
Solar radiation (shortwaves) passes rather freely through earth’s atmosphere, but the earth’s re-emitted
infrared radiation(longwaves) energy either fits through a narrow window or is absorbed by greenhouse gases and re-radiated toward earth.
Atmospheric Window
Between 8 and 11μm neither water vapor nor CO2 readily absorb these wavelengths in the Infrared Radiation (longwave) scale. Because this energy passes upward through the atmosphere and out into space, this wavelength range is known as the “atmospheric window”.
