Chapter 16
Radiation
Every object above absolute zero radiates electromagnetic waves. Long waves are radio waves Short waves are x rays Long waves are red Short waves are violet
Because of trapped air inside, snow is a
Good insulator
In a mixture of hydrogen gas, oxygen gas, and nitrogen gas, the molecules with the greatest average speed are those of
Hydrogen
Conduction
Transfer of internal energy by electron and molecular collisions within a substance, especially a solid ▫️good conductors conduct heat quickly ▫️silver, copper, and other solid metals
Radiation
Transfer of electromagnetic energy through empty space
Convection
Transfer of heat involving only bulk motion of fluids.
Convection
Warm air expands, becomes less dense, and is buoyed upward. - It rises until its density equals that of the surrounding air. ▫️gases cool when expand and warm up when compressed
A parcel of warmed air rises due to
buoyancy
A red-hot piece of coal will cool quicker in a
cold room
Substances absorb heat energy by the process of
conduction, convection, radiation
If air were a better conductor, at nighttime Earth would be
considerably colder
A region of expanding air tends to
cool
If a volume of air is warmed, it expands and tends to
cool
If the composition of the upper atmosphere were altered to permit a greater amount of terrestrial radiation to escape, Earth would be
cooler
If a pizza radiates more energy than it absorbs, its temperature
decreases
The heat we enjoy on a sunny day is due mainly to the Sun's
enormous size
Energy transfer by convection is primarily restricted to
fluids
Solar power is used in many parts of the world for
generating electricity and heating water
A good absorber of radiation is a
good emitter of radiation
A bridge is more likely to be ice covered than the roadway on a cold day because
heat upwelling from the ground below is absent on a bridge
An apple pie will be a net emitter of energy when its temperature is
higher than its surroundings
If a pizza absorbs more energy than it emits, its temperature
increases
When a volume of air is compressed, air temperature
increases
On a cold day your feet feel warmer on a rug than on a tile floor because a rug
is a poorer conductor
When an object absorbs as much as it radiates
it remains at about the same temperature.
Hydrogen and oxygen molecules in a sample of gas have the same temperature. This means the hydrogen molecules, on average, have the same
kinetic energy, but more speed
If a poor absorber of radiation were a good emitter, its temperature would be
less than its surroundings
Metals are good conductors of both heat and electricity due to
looseness of outer electrons in metal atoms
The reason you can walk barefoot on red-hot coals of wood without burning your feet mainly involves
low conductivity of the coals
A blueberry pie will be a net absorber of energy when its temperature is
lower than its surroundings
The lower the temperature of an object, the
lower the frequency of radiation it emits and the longer the wavelengths it radiates
Which of these are good conductors?
none of the above (feathers,snow,wood)
A good reflector of radiation is a
poor absorber of radiation
A good heat conductor is
poor insulator
A Thermos bottle has double glass walls with silver coating on the glass surfaces that face each other. The silver coating reduces energy transfer by
radiation
The form of heat transfer that doesn't depend on a medium is
radiation
The planet Earth loses heat primarily by
radiation
Which body glows with electromagnetic waves? A. Sun B. Earth C. Both A and B. D. None of the above
Both A and B.
You can safely hold your fingers on both sides of a candle flame, but not directly above the flame, due mainly to
Convection
Terrestrial radiation is
Emitted by earth
Which melts faster is sunlight dirty snow or clean snow
Dirty snow
Insulation
Doesn't prevent heat flow, just slows the rate at which internal energy flows
Insulators
Poor conductors are called insulators. ▫️Have molecules with tightly held electrons in a substance vibrate in place and transfer energy slowly- these are good insulators (and poor conductors). ▫️glass, wool, wood, paper, cork, plastic foam, air. ▫️substances that trap air are good insulators
Blow on your hand with your mouth open. Then do the same with your lips puckered and you'll find
The breath from puckered lips is cooler
Wind
Winds are the result of uneven heating of the air near the ground
If there were no greenhouse effect, Earth's average temperature would likely be
a frigid -18°C.
The temperature of outer space is
about 2.7 kelvin
Objects that radiate relatively well
absorb radiation relatively well
Every equation in physics reminds us of a lesson: we can never change only one thing. When we change the composition of the atmosphere we likely also change
all of the above
Wood is a poor conductor
all of the above
Glass in a florist's greenhouse acts as a one-way valve in that it
allows high-frequency waves in and blocks low-frequency waves exiting
If you were caught in freezing weather with only a candle for heat, you would be warmer in
an igloo
A bare roof on a warmly heated home on a snowy day indicates
an unwanted flow of heat, poor insulation, and fairly good conductivity
The higher the temperature of an object, the
shorter the wavelengths it radiates.
In practice, a good insulator
slows heat flow
It is commonly thought that a can of beverage will cool faster in the coldest part of a refrigerator. Knowledge of Newton's law of cooling
supports this common knowledge
Sun's radiant energy is composed of shorter wavelengths than Earth's due to Sun's greater
surface temperature
Both black and white road surfaces absorb sunlight. The warmer road surface at the end of a sunny day is the
the black surface
A water-filled paper cup held in a flame will not catch fire. This is because
the paper cup cannot become appreciably hotter than the water it contains
Waves emitted by the Sun and terrestrial wave emissions are
the same except for their frequencies and wavelengths.
At the same temperature, which has greater average speed in the air?
very light molecules
Newton's law of cooling applies to objects undergoing
warming and cooling
Which is the most abundant greenhouse gas in Earth's atmosphere?
water vapor
When you touch a nail stuck in ice, energy flows from
your hand to the ice
A block of wood and a block of copper will feel neither hot nor cold to the touch when they each have
your temperature
Reflection
▫️Any surface that reflects very little radiant energy appears dark ▫️any surface that reflects a lot of radiant energy appears lighter