Deck 7: Heat and Phase Transitions

Question 1

Why does an ice cube feel cold?

A) Heat from your hand enters the cube by convection.
B) Cold from the cube enters your hand by convection.
C) Heat from your hand enters the cube by conduction.
D) Cold from the cube enters your hand by conduction.

Answer 1

Heat from your hand enters the cube by conduction.

Question 2

Wind is one of nature's ways of transferring energy through

A) conduction.
B) convection.
C) transmission.
D) radiation.

Answer 2

convection.

Question 3

Why are good thermal conductors generally good electric conductors also?

A) Heat and electricity are the same things.
B) The molecules in both don't move around very much.
C) Electron motion is responsible for determining both properties.
D) The answer depends on the specific metal.

Answer 3

Electron motion is responsible for determining both properties.

Question 4

A pedestrian bridge crosses a street. This bridge is entirely supported by columns from below. A gap at each end of the bridge separates the bridge's surface from the sidewalks leading to the bridge. The width of each gap changes with time. This width is smallest

A) on hot days.
B) at noon.
C) at midnight.
D) on cold day.

Question 5

The neighborhood children are playing and one has lost a pocketful of change. As a result they all decide to do a close inspection of the sidewalk. They notice that there are gaps in between the sidewalk filled with a felt - like material. These gaps will prevent

A) high stress due to electron "collisions"
B) high stress due to thermal expansion.
C) high stress due to brittleness
D) high stress due to the weight of the sidewalk

Question 6

People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps because

A) conduction carries heat downward toward the fire fighter and the aluminum tent conducts that heat harmlessly into the ground.
B) radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation.
C) convection carries heat downward toward the fire fighter and the aluminum tent blocks most of the heat carried by convection.
D) both conduction and radiation carry heat downward toward the fire fighter and the aluminum tent blocks most of that heat.

Question 7

You are a mechanic in a garage and are working on a carburetor that is made of metal, has a glass inspection window and plastic gears for the choke. If all three types of material are at the same temperature and each type of material is in contact with the other two, then

A) heat will flow from the plastic to the glass, and from the glass to the metal.
B) heat will flow from the metal to the glass, and from the glass to the plastic.
C) heat will flow from the glass to both the plastic and the metal.
D) no heat will flow between any parts.

Question 8

Suppose you are teaching a science course and have prepared a demonstration to teach how a thermometer works. When you plunge the thermometer into hot water, one of your students points out that the mercury in the thermometer actually went down a little bit before it shot up. It behaved in such a way because

A) The water pressure squeezed in on the mercury.
B) The mercury contracted at first because of the temperature shock.
C) The glass expanded before the mercury had a chance to, creating space.
D) The thermometer lost heat to the surrounding water.

Question 9

The surface of the moon is exposed to full solar radiation because it has no atmosphere. Why then does the moon not heat up endlessly until it disintegrates?

A) Convection in the soil carries energy away.
B) Its temperature rises until it is able to radiate heat away into space as fast as it arrives from the sun.
C) It has disintegrated but the light just hasn't reached us yet.
D) Because it is isolated from the sun by empty space, the sun's heat can't reach it (only light can) and they don't experience any changes in temperature.

Question 10

Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun rises near the seashore.

A) The surface wind will blow from the land toward the water.
B) The surface wind will blow alternately back and forth along the shore, parallel to the boundary between land and water. It will reverse directions every few minutes.
C) The surface wind will blow steadily in one direction along the shore, parallel to the boundary between land and water.
D) The surface wind will blow from the water toward the land.

Question 11

A common glass thermometer contains a red or silver liquid that rises upward in a glass tube as the temperature of the thermometer increases. The liquid moves up the tube because

A) only the glass contracts as its temperature decreases, so the liquid moves up the tube to occupy more of the tube's internal space.
B) while both the glass and the liquid contract as their temperatures increase, the glass contracts more rapidly than the liquid does.
C) the pressure of gas above the liquid decreases as its temperature rises and the liquid is sucked upward in the glass tube.
D) while both the glass and the liquid expand as their temperatures increase, the liquid expands more rapidly than the glass does.

Question 12

Trace the transfer of energy that comes from your food.

Question 13

Suppose you take an interest in astronomy. You are at an astronomy conference and you are listening to a presentation where a scientist is describing a new planet. The scientist says "The planet Xhhroylg is completely solid and convects heat from its inner core towards the surface at a rapid rate. Although no electromagnetic radiation escapes through its dense atmosphere, its heat conducts through the reaches of outer space and that explains how it cools down." Please discuss three instances where, scientifically, this presenter is incorrect.

Question 14

A thermos may be thought of as a glass bottle within another, which are joined (sealed) together at the top. The space between the bottles may be evacuated, and the surface of the inner bottle may be silvered (coated with reflective material).What heat transfer mechanisms, if any would be inhibited by
-A silvered, evacuated thermos;

Question 15

A thermos may be thought of as a glass bottle within another, which are joined (sealed) together at the top. The space between the bottles may be evacuated, and the surface of the inner bottle may be silvered (coated with reflective material).What heat transfer mechanisms, if any would be inhibited by
-a clear thermos, not evacuated;

Question 16

A thermos may be thought of as a glass bottle within another, which are joined (sealed) together at the top. The space between the bottles may be evacuated, and the surface of the inner bottle may be silvered (coated with reflective material).What heat transfer mechanisms, if any would be inhibited by
-a clear, evacuated thermos, and

Question 17

A thermos may be thought of as a glass bottle within another, which are joined (sealed) together at the top. The space between the bottles may be evacuated, and the surface of the inner bottle may be silvered (coated with reflective material).What heat transfer mechanisms, if any would be inhibited by
-a silvered thermos only.

Question 18

Why does the handle of a metal spoon submerged in boiling soup feel hot ?

A) from the soup is transferred through the spoon by convection.
B) The spoon has given up all its cold to the soup.
C) Heat from the soup is transferred through the spoon by conduction.
D) Heat from the soup is transferred through the spoon by radiation.

Question 19

The gulf stream is one of nature's ways of transferring energy through

A) conduction.
B) convection.
C) transmission.
D) radiation.

Question 20

When cooking a potato in a conventional oven it is useful to stick a nail in it, which makes it cook faster. This is because

A) the nail is a good radiator of heat
B) the nail promotes convection in the potato
C) the nail is a good conductor of heat
D) the nail gets much hotter than anything in the oven

Question 21

Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun sets near the seashore.

A) The surface wind will blow from the land toward the water.
B) The surface wind will blow alternately back and forth along the shore, parallel to the boundary between land and water. It will reverse directions every few minutes.
C) The surface wind will blow steadily in one direction along the shore, parallel to the boundary between land and water.
D) The surface wind will blow from the water toward the land.

Question 22

In addition to heat energy, another product of fires is dangerous smoke and other chemicals. This fact is the reason for a ________ ________ in a furnace.

A) Heat Exchanger
B) Stock Exchanger
C) Heat Stabilizer
D) Catalytic Converter

Question 23

You are talking with your fiancée and looking up into a beautiful night sky and she comments "You know, it is sad that we couldn't tell if there were any black objects out there no matter how hot they were because a black object would never emit light at any temperature." You would comment:

A) Nothing. Even though you know it is a misconception and that black objects absorb and emit radiation perfectly, you don't want to ruin the evening.
B) Nothing, because she is correct.
C) Nothing, because black objects absorb light but don't emit any.
D) Nothing, because black objects emit light but don't absorb any.

Question 24

In the poem "When You Are Old" by William Butler Yeats there is the following concluding line: "and bending down beside the glowing bars, murmur, a little sadly, how love fled and paced upon the mountains overhead and hid his face amid a crowd of stars." The glowing bars refer the metal bars that hold wood in a fireplace and they are transmitting heat energy by

A) radiation only
B) radiation and conduction.
C) conduction only
D) convection

Question 25

Which temperature scale has 373 as the boiling point of water?

A) Fahrenheit
B) Celsius
C) Centigrade
D) Kelvin

Question 26

You are hired as an engineer at a thermometer factory. Suppose you built a water thermometer by replacing the mercury in a mercury thermometer with water. You want to measure temperatures above freezing with it. How would it behave as the temperature drops from 5^o C to 1^o C?

A) The reading will decrease and then begin increasing.
B) The reading will steadily decrease.
C) The reading will steadily increase
D) The reading will increase and then begin decreasing.

Question 27

In making ice cream, the flavored cream is in a container in contact with ice. In order to freeze the ice cream why is it essential to make the ice melt at a very low temperature?

A) Liquid water has a high specific heat.
B) The melted ice makes it easier for the air to remove energy from the ice cream.
C) The low temperature of the ice as well as its melting removes energy from the flavored cream, causing it to freeze.
D) It is easier to stir things around with the ice melted.

Question 28

In making ice cream, the flavored cream is in a container in contact with melting ice. When the ice cream freezes it give energy up to the ice / water mixture. What happens to the temperature of the ice / water mixture?

A) It will increase from the ice cream's heat.
B) It will not change because the energy is going into its melting the ice.
C) It will increase from stirring.
D) It decreases.

Question 29

A popular classroom demonstration involves placing a paper cup with water in it on a burner, and boiling the water in the cup. Although part of the cup may burn, the part containing the water does not because

A) paper is a poor conductor of heat.
B) it all happens too quickly for the paper to burn.
C) the water absorbs most of the heat from the flame.
D) the evolving steam burns the paper on the cup above the water line.

Question 30

Some scientists assert that there would be no life on earth if ice did not have a molecular structure with a lot of open space because

A) ice would be so light that it could never form, leaving too much water on the Earth's surface.
B) ice would be less dense than it is now and float too much
C) ice would be denser than water and having a solid sink in its own liquid form would violate the conservation of energy.
D) the density of ice would be greater than water and lakes would freeze solid - from the bottom up.

Question 31

You get a job as a dish washer to help with your college bills. The first thing the management tells you is to be very careful of the steam - it is exceedingly dangerous. In fact, steam at 100^o C can burn you much more than water at 100⁰ C. Please explain.

Question 32

Why do you feel cold (even on a very hot day) when you step out of a swimming pool and are wet?

Question 33

Why is it possible to get hypothermia (lowering your body temperature to a dangerous level) by spending a long time without any protective clothing in water that is kept as warm as 85^o F?

Question 34

Why is the temperature of coastal cities fairly steady, but in the desert it can vary considerably between night and day?

Question 35

Ice is

A) amorphous
B) very disordered
C) crystalline
D) just like liquid water only it move slower

Question 36

Which temperature scale has 273 as the boiling point of water?

A) Fahrenheit
B) Celsius
C) No scale
D) Kelvin

Question 37

Melting is a _______ ______ that requires energy ________ for the melting system.

A) phase transition; input
B) chemical change; input
C) phase transition; release
D) chemical change; release

Question 38

Freezing is a _______ ______ that requires energy ________ for the melting system.

A) phase transition; input
B) chemical change; input
C) phase transition; release
D) chemical change; release

Question 39

In studying tornado formation, it is thought that water condensing is a very important driving mechanism for the violent storm because

A) Water condensing takes a lot of energy from the environment.
B) Water condensing provides momentum.
C) Water condensing releases a lot of energy into the environment.
D) Water condensing changes the viscosity of the air which helps the tornado rotate.

Question 40

Your friend left their science project off until the "night before" and now they are frantic to build a homemade weather station that can measure relative humidity. They build the standard two - thermometer setup but their water had just been shut off and so they use salad oil on the wet bulb thermometer. Please describe how well their instrument will work and the physics behind your answer.

Question 41

You are watching a science fiction movie where people on a space ship are traveling around the universe observing stars with different temperatures. Which of the following stars has the lowest surface temperature?

A) A bluish star
B) A yellowish star
C) The sun
D) A reddish star

Question 42

If you double the absolute temperature of a star, its power output increases by a factor of

A) 2
B) 4
C) 8
D) 16

Question 43

If you double the radiating surface area of a star, its power output increases by a factor of

A) 2
B) 4
C) 8
D) 16

Question 44

A shiny, white transparent surface prevents heat transfer because

A) It has emissivity of zero and reflects all light that strikes it.
B) It has emissivity of 1 and reflects all light that strikes it.
C) It has emissivity of zero and absorbs all light that strikes it.
D) It has emissivity of 1 and absorbs all light that strikes it.

Question 45

Housing and natural animal insulation works because

A) the insulating materials are poorer heat conductors than air.
B) the insulating materials trap air and prevent convection.
C) the insulating materials prevent radiation
D) the insulating materials reflect radiation

Question 46

Some biologists imagine what it would be like to have warm - blooded fish. Suppose that fish really were warm - blooded instead of cold - blooded. Please discuss a change in the animal's food intake.

Question 47

Some biologists imagine what it would be like to have warm - blooded fish. If fish really were warm - blooded they would have to increase their food intake by a considerable amount. Whales and marine mammals get around this by having thick layers of fat. Please explain why the fat is helpful in maintaining marine mammals' body temperatures.

Question 48

Let's say you are an astronomer and are making a model of the universe. You are re-designing stars, to which you can make some changes. You can independently alter the star's dominant color and also alter its radius (surface area). In the table below please indicate which combinations of color change and radius change could possibly yield a brighter star, and offer a brief explanation..

Question 49

Low-E coatings are placed on house windows because

A) the coating prevents convective heat transfer.
B) radiative heat transfer is a big problem for clear windows but the Low - E coating reflects the visible light.
C) radiative heat transfer is a big problem for clear windows but the Low - E coating reflects ultraviolet light.
D) radiative heat transfer is a big problem for clear windows but the Low - E coating reflects infrared light.