Chapter 7 Exam 2
After climbing out of the swimming pool, the chill you often feel is mainly due to
evaporation
Compared to a glass of ice water with ice, a glass of plain ice-cold water without ice on a warm day will warm up
faster
A good absorber of radiation is a
good emitter of radiation
Which requires more energy
changing 1 gram of 100°C water to 100°C steam
Why does the direction of coastal winds change from day to night?
Air flows toward the warmer surface where it rises, reversing when the relative temperatures of the land and water reverse.
Warm air rises because faster moving molecules tend to move to regions of less
Both Density and Pressure
The dew that forms on a cold soda can when taken from a refrigerator is due to
Condensation
What is condensation, how does it differ from evaporation, and why is it a warming process?
Condensation is the change in phase from gas to liquid and the opposite of evaporation. Gas molecules near a liquid surface are attracted to the liquid, strike it with increased KE, and thereby warm the liquid.
What is the purpose of the copper or aluminum layer on the bottom of a stainless-steel pot?
Copper and aluminum are better conductors than stainless steel, and therefore transfers heat more quickly to the pot's interior.
Distinguish between evaporation and boiling.
Evaporation is a phase change at the surface of a liquid; boiling is a phase change that occurs throughout a liquid, producing bubbles.
What is evaporation, and why is it a cooling process?
Evaporation is the cooling process, change of phase from liquid to gas. As fast-moving molecules in a liquid escape into the air, slower ones on average are left behind, thereby cooling the water.
You enter a crowded and chilly classroom early in the morning on a cold winter day. Before the end of the hour, the room temperature increases to a comfortable level, even if heat is not provided by the school heating system. Why the difference?
Every student radiates about the same amount of heat as a 100-W incandescent bulb. So heat radiated by you and your classmates increases the temperature of the room.
What happens to the temperature of air when it expands?
Expanding air cools so its temperature is reduced.
By what means is heat transferred by convection?
Heat is transferred by the movement of fluids.
If a pizza absorbs more energy than it emits, its temperature
Increases
Practice Problems - Does a good insulator prevent heat from getting through it, or does it simply delay its passage?
Insulation delays heat transfer.
The average frequency of radiant energy is directly proportional to the
Kelvin temperature of the emitter.
Why does increasing the temperature of a solid make it melt?
Molecular motion increases and molecules shake apart with increasing temperature.
Why does decreasing the temperature of a liquid make it freeze?
Molecular motion slows allowing molecules to bind together.
Do all molecules in a liquid have about the same speed, or do they have a wide variety of speeds?
Molecules in a liquid have a wide variety of speeds.
A candle will stay lit inside the space shuttle when it is on the launch pad but not when it is in orbit. Why?
No gravity, can't distinguish density
If you hold one end of a metal bar against a piece of ice, the end in your hand will soon become cold. Does cold flow from the ice to your hand?
No, cold doesn't move, it's an absence of heat
Which of these are good conductors? Feathers Wood or Snow
None of the above
Sublimation is a change of phase from solid to gas without
Passing through the liquid phase
What is sublimation?
Sublimation is the direct change of phase from solid to gas, skipping the liquid phase.
Which is not a phase of matter?
Vacuum
You can determine wind direction by wetting your finger and holding it up in the air. Explain.
When a wet finger is held to the wind, evaporation is greater on the windy side, which feels cool. The cool side of your finger is windward.
When air rapidly expands it generally
cools
If a good absorber of radiant energy were a poor emitter, its temperature compared with its surroundings would be
higher
A water filled paper cup held in a flame will not catch fire because
the paper cup cannot become appreciably hotter
Convection currents in the air near a seashore are produced by
unequal heating of land and water
When water vapor in the atmosphere condenses, the air around it
warmer
When testing for the hotness of a clothing iron, it is best to
wet your finger first and touch the iron briefly
As a block of ice at 0°C melts, the block absorbs energy
without a temperature change.
When you touch a block of ice, energy flows from
your hand to the ice
