chapter15&16 Flashcards
When we speak about heat we refer to ___________.
energy in transit
In which direction does heat flow spontaneously between hot and cold objects?
From high temperature to low temperature
How is heat similar to and different from internal energy?
They are both forms of energy, but heat flows, whereas internal energy does not
Does a hot object contain internal energy or does it contain heat?
Internal energy
The air in your room is composed of molecules that have
a wide variety of speeds
Temperature is most closely related to molecular
kinetic energy
Which temperature scales have equal sized degrees?
Celsius and Kelvin
When you touch a cold piece of ice with your finger, energy flows
from your finger to the ice.
Heat energy travels from an object with a high
temperature to an object with a lower temperature
Hot sand cools off faster at night than plants and vegetation. This indicates that the specific heat capacity for sand is ___________.
less than that of plants
Does a substance that heats up quickly have a high or a low specific heat capacity?
A low specific heat capacity
How does the specific heat capacity of water compare with the specific heat capacities of other common materials?
Water has a higher specific heat capacity than most common materials
Why do substances expand when their temperature is increased?
Higher-temperature substances have greater molecular motion
Why is ice less dense than water?
Ice crystallizes with an open structure, and the gaps that form between the water molecules in ice increase its volume.
Why does all the water in a lake have to be cooled to 4°C before the surface water can be cooled below 4°C?
When water is cooled to 4°C, it sinks and deeper, warmer, water rises to the surface
When you touch a hot potato with your finger, energy flows
from the potato to your finger
The amount of heat needed to raise the temperature of 1 gram of water by 1°C is
4.19 Joules
When 10 grams of hot water cool by 1°C, the amount of heat given off is
41.9 Joules
Pour a liter of water at 40°C into a liter of water at 20°C and the final temperature of the two becomes
at or about 30°C.
Pour two liters of water at 40°C into one liter of water at 20°C and the final temperature of the two becomes
more than 30°C
A substance with a high thermal inertia has a high
specific heat capacity
Materials composed of molecules that absorb large amounts of energy in the form of internal vibrations and rotations have
high specific heats
Aluminum has a higher specific heat capacity than iron. This means that for equal masses of aluminum and iron, the metal that heats more quickly when the same amount of heat is applied is
iron
A substance that cools down faster than others has a
low specific heat capacity
A substance that heats up relatively slowly has a
high specific heat capacity
When most substances are heated, molecules inside move faster and take up more space, resulting in thermal
expansion
When an iron ring is heated, the hole becomes
larger
Due to the presence of ice crystals in nearly frozen liquid water, the density of water is
lower
If you wish to expand the volume of a sample of water at 4°C
- lower its temperature a bit
- raise its temperature a bit
When water at 4°C is heated it expands. If it is instead cooled it will
also expands
Before ice can form on a lake, all the water in the lake must be cooled to
4°C
If you touch the metal sides in an oven with your bare hand, you’re in trouble. But hold your hand briefly in the oven air and you’re okay. What does this tell you about the relative conductivities of metal and air?
Metal is a good conductor of heat, whereas air is a terrible conductor of heat
Why are materials such as wood, fur, feathers, and even snow good insulators?
Outer electrons in these materials are firmly attached
Does a good insulator prevent heat from escaping or slow its passage?
Insulators slow the passage of heat
Why does the direction of coastal winds change from day to night?
The specific heat of water is greater than the specific heat of land. Water cools more slowly at night. The temperature difference drives convection and offshore winds.
Heat travels from the Sun to Earth by the process of _________.
radiation
Relatively speaking, do high-frequency waves have long wavelengths or short wavelengths? Name an electromagnetic wave with higher frequency than blue light.
short, ultraviolet
How does the peak frequency of radiant energy relate to the absolute temperature of the radiating source?
The peak frequency increases as temperature increases
What is terrestrial radiation?
Terrestrial radiation is infrared radiation emitted by Earth’s surface
Since all objects emit energy to their surroundings, why don’t the temperatures of all objects continuously decrease?
Objects that are good emitters are equally good absorbers, so they absorb radiation as well as emit it
What determines whether an object is a net absorber or a net emitter of radiant energy at a given time?
It is determined by the temperature of the object relative to its surroundings. Hotter objects are net emitters
Which will normally warm faster: a black pot of cold water or a silvered pot of cold water? Which will cool faster?
black, black
Can an object be both a good absorber and a good reflector at the same time?
No. A good absorber reflects very little light
What type of gas absorbs and re-emits infrared radiation?
greenhouse gases
Newton’s law of cooling applies to objects that undergo _________.
cooling or warming
Which will undergo the greater rate of cooling: a red-hot poker in a warm oven or a red-hot poker in a cold room (or do both cool at the same rate)?
The poker in the cold room cools fastest.
Metals are good conductors of both heat and electricity due to
looseness of outer electrons in metal atoms
Which of these are good insulators?
- feathers.
- snow.
- wood.
On a cold day your feet feel warmer on a rug than on a tile floor because a rug
is a poorer conductor
A block of wood and a block of copper will feel neither hot nor cold to the touch when they each have
your temperature
If you were caught in freezing weather with only a candle for heat, you would be warmer in
an igloo
The reason you can walk barefoot on red-hot coals of wood without burning your feet mainly involves
low conductivity of the coals
The form of heat transfer that doesn’t depend on a medium is
radiation
The higher the temperature of an object, the
shorter the wavelengths it radiates
If a pizza radiates more energy than it absorbs, its temperature
decreases
An apple pie will be a net emitter of energy when its temperature is
higher than its surroundings.
Which body glows with electromagnetic waves?
- the Earth
- you and your classmates
- the Sun
Waves emitted by the Sun and terrestrial wave emissions are
the same except for their frequencies and wavelengths.
Long ago a runaway greenhouse effect transformed the planet
venus
When coal dust is spread on snow on a sunny day
more melting occurs
Heat normally flows from objects of high
temperature to objects of low temperature
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
When a hot object makes thermal contact with a cold object, the direction of
internal energy flow is from hot to cold
The amount of heat needed to raise the temperature of 1 g of water by 1°C is ___________.
1 calorie
If the temperature of a sample of water at 0°C is slightly increased, its volume
decreases
If the temperature of a sample of water at 4°C is slightly increased, its volume
increases
If the temperature of a sample of water at 4°C is slightly lowered, its volume
increases
If you measure the width of an outdoor barn with a steel tape on a very cold day, your measured width will be
a bit long
The lower the temperature of an object, the
- lower the frequency of radiation it emits.
- longer the wavelengths it radiates
A liter of cold water will warm faster in sunlight in a
black pot
In practice, a good insulator
slows heat flow
When an object absorbs as much as it radiates
it remains at about the same temperature
A liter of hot water will cool to room temperature faster in a
black pot
A red-hot piece of coal will cool quicker in a
cold room
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
The planet Earth loses heat primarily by
radiation
A good absorber of radiation is a
good emitter of radiation
Aluminum has a specific heat capacity more than twice that of copper. Place equal masses of aluminum and copper wire in a flame and the one to undergo the fastest increase in temperature will be
copper
Which unit represents the most energy?
Calorie
The moderate temperatures of islands throughout the world has much to do with water’s
high specific heat capacity
Terrestrial radiation is
emitted by Earth
Which temperature scale has the smallest sized degrees?
Fahrenheit
A temperature difference of 10 Celsius degrees is also equal to a temperature difference of 10 on the
kelvin scale
Room temperature on the Kelvin scale is about
300 k
Heat energy is measured in units of
- calorie
- joules
The specific heat capacity is highest for substances that absorb or release large quantities of heat for correspondingly
small temperature changes
A substance that heats up relatively quickly has a
low specific heat capacity
The fact that desert sand is very hot in the day and very cold at night is evidence that the specific heat capacity of sand is relatively
low
One of water’s interesting thermal properties is that when heated it takes a relatively
long time in changing temperature
If the specific heat capacity of water were lower than it is, a nice hot bath would be a
shorter experience
When we enlarge a photograph of an iron ring, the image of the hole becomes
larger
When a bimetallic bar made of copper and iron strips is heated, the bar bends toward the iron strip. The reason for this is
copper expands more than iron
Because of trapped air inside, snow is a
both a good insulator and a poor conductor
If a volume of air is warmed, it expands and tends to
cool
Blow on your hand with your mouth open. Then do the same with your lips puckered and you’ll find
- a difference in temperatures.
- the breath from puckered lips is cooler
Molecules in a region of expanding air more often collide with neighboring molecules that are
receding
A region of expanding air tends to
cool
A parcel of warmed air rises due to
buoyancy
Objects that radiate relatively well
absorb radiation relatively well
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
If a poor absorber of radiation were a good emitter, its temperature would be
less than its surroundings.
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
- its reflectivity.
- Earth’s climate.
- its average temperature.
- its transparency
