Chapter 11 Concept Questions

Complete the following statement: The term heat most accurately describes 1/1 a) the flow of energy due to a temperature difference. b) the molecular motion inside of an object. c) the internal energy of an object. d) a measure of how hot an object is. e) the absolute temperature of an object.

A

A certain amount of heat Q is added to materials A, B, and C. The masses of these three materials are 0.04 kg, 0.01 kg, and 0.02 kg, respectively. The temperature of material A increases by 4.0 C° while the temperature of the other two materials increases by only 3.0 C°. Rank these three materials from the largest specific heat capacity to the smallest value. 1/1 a) A > B > C b) B > C > A c) C > B > A d) B = C > A e) A > B = C

B

A candle is burning at the bottom of a vertical tube. A second vertical tube is inserted in the tube just above the candle as shown. What will happen if the second tube is removed? 1/1 a) The flame will go out. b) The flame will burn less brightly. c) The flame will continue to burn the same as before. d) The flame will burn more brightly.

a

Just before spring arrives, an airplane flies over some mountains and drops black soot on the snow and ice. This procedure is done to prevent flooding of the valley below when the warmer weather arrives with spring. How does this procedure prevent flooding? 1/1 a) The areas where the soot fails should melt earlier than those without the soot as sunlight will be absorbed. Melting the snow gradually reduces the amount that will melt as temperatures rise in spring. b) The soot increases the temperature at which snow and ice melt causing the areas that have soot to melt later. c) The soot lowers the temperature at which snow and ice melt causing the areas that have soot to melt earlier. d) The soot has a higher thermal conductivity than water and ice and can transmit heat from the air more efficiently to the snow and ice underneath the soot. e) Air convection warms the soot covered snow more efficiently than the snow wit

a

One end of an aluminum rod is maintained at 0 °C in an ice water bath. The other end of the rod is maintained at 100 °C in a boiling water bath. The amount of heat the flows through the rod via conduction during a time interval t is not dependent on which one of the following parameters? 1/1 a) the mass of the rod b) the length of the time interval c) the length of the rod d) the temperatures at the ends of the rod e) the thermal conductivity of aluminum

a

Randy has placed 10 thermometers at different depths and radii within a pot of water on an electric stove. He then turns on the heating element under the pot and watches the thermometers. He notices that the temperature of the water at the ten locations is approximately the same as the temperature increases from room temperature to 100 °C. Which one of the flowing statements best describes the nearly uniform temperature throughout the pot? 1/1 a) Convection currents appear that evenly distribute heat throughout the pot. b) Heat is rapidly conducted from the bottom of the pot to the top because of the temperature gradient that exists between the bottom of the pot and the top. c) The pressure at a given depth in the water must remain constant. d) The water is heated via radiation. The bottom of the pot is hotter than the water and all water molecules are irradiated equally. e) The water molecules near the bottom recei

a

Two balls, one made of copper and one made of gold, have the same mass and temperature. The same amount of heat is added to each sphere, but the final temperature of the two spheres is different. Which one of the following statements best explains the reason for these temperature differences? 1/1 a) The specific heat capacity of the two spheres is different. b) The density of the two spheres is different. c) The volumes of the two spheres are different. d) The coefficient of volume expansion of the two spheres is different. e) The latent heat of vaporization of the two spheres is different

a

What does the heat capacity of an object measure? 1/1 a) the amount of energy required to change the temperature of an object b) the total amount of energy an object can store c) the thermal potential energy of the object d) the amount of work done by the object e) the amount of energy required to melt a solid object

a

What is the final temperature when 2.50 × 10^5 J are added to 0.950 kg of ice at 0.0 °C? 1/1 a) 0.0 °C b) 4.2 °C c) 15.7 °C d) 36.3 °C e) 62.8 °C

a

Which one of the following objects will be most efficient in losing heat? Assume that all of the objects are at the same temperature initially. 1/1 a) a graphite cube with a black, rough surface surrounded by air b) a polished silver cube in an evacuated chamber c) a polished silver cube surrounded by air d) a graphite cube with a black, rough surface in an evacuated chamber e) a polished graphite cube surrounded by air

a

Which one of the following statements concerning the Stefan-Boltzmann equation is true? 1/1 a) The equation can be used to calculate the power absorbed by any surface. b) The equation applies only to perfect absorbers. c) The equation applies only to perfect radiators. d) The equation is valid with any temperature units. e) The equation describes the transport of thermal energy by conduction.

a

Consider the following substances all at room temperature: (1) aluminum (k=236 W/mK), (2) copper (k=401 W/mK), (3) steel (k=40 W/mK), and (4) wood (k=0.1 W/mK). Which one would feel the coolest if held in your hand (which is at a temperature above room temperature)? 1/1 a) 1 b) 2 c) 3 d) 4 e) All would feel the same temperature.

b

The fresh seafood was shipped in dry ice. By the time the package arrived at its destination, half of the dry ice had sublimed. Which one of the following statements is another way of expressing what the dry ice did? 1/1 a) The dry ice had gone from a solid to a liquid state. b) The dry ice had gone from a solid to a gaseous state. c) The dry ice had condensed. d) The dry ice had gone from a liquid into a gaseous state. e) The dry ice had chemically reacted with the seafood and was absorbed by it.

b

Two bars are placed between two plates: one at temperature T_HOT and one at T_COLD. The thermal conductivity of bar A is three times that of bar B. The cross-sectional area of bar A is one-half that of bar B. There is no heat loss from the sides of the bars. Which one of the following statements correctly describes the heat conducted by the two bars in a time interval t? 1/1 a) The amount of heat conducted by bar A is 3 times that conducted by bar B. b) The amount of heat conducted by bar A is 3/2 times that conducted by bar B. c) The amount of heat conducted by bar A is the same as that conducted by bar B. d) The amount of heat conducted by bar A is 2/3 times that conducted by bar B. e) The amount of heat conducted by bar A is 1/3 times that conducted by bar B.

b

Two sealed containers are initially at the same temperature and have the same dimensions. The outer surfaces of container A appear to be polished aluminum. The outer surfaces of container B are roughened gray cast iron. A large, bright incandescent light bulb is brought near both containers and shines on them for equal amounts of time from the same distance. Within which container, if either, will the temperature increase at the fastest rate? 1/1 a) A b) B c) The temperature of both containers will increase at the same rate.

b

Under which one of the following circumstances is heat transferred via convection? 1/1 a) A steel disc is heated to 800 °C within an evacuated furnace chamber. b) Ice cubes dropped into a glass of water at room temperature begin to melt. c) An electrically heated rod is plugged into a metal plate used for cooking. The temperature of the metal plate then increases. d) As a jogger runs, heat generated in her body passes through fat cells under her skin before passing through her skin. e) The temperature of a black cast iron frying pan increases as sunlight shines on it.

b

Which of the following describes the energy radiated from an object at Kelvin temperature T? 1/1 a) Planck distribution b) Stefan-Boltzmann law c) Maxwell blackbody law d) Bose-Einstein equation e) Klein-Gordon equation

b

Which of the following substances would be the most effective in cooling 0.300 kg of water at 98 °C? 1/1 a) 0.100 kg of lead at 22 °C b) 0.100 kg of water at 22 °C c) 0.100 kg of glass at 22 °C d) 0.100 kg of aluminum at 22 °C e) 0.100 kg of copper at 22 °C

b

Which one of the following statements is the definition of the specific heat capacity of an object? 1/1 a) The specific heat capacity is the amount of energy per unit mass to raise the temperature of the object from its freezing point to its boiling point. b) The specific heat capacity is the amount of energy per unit mass to raise the temperature of the object by 1 C°. c) The specific heat capacity is the temperature of the object divided by its density. d) Given one gram of the material, the specific heat capacity is the amount of energy to change the material from solid to liquid. e) Given one gram of the material, the specific heat capacity is the amount of energy to change the material from a solid to a gas

b

A swimming pool has a width of 9.0 m and a length of 12.0 m. The depth of the water is 1.83 m. One morning, the temperature of the pool water was 15.0 °C. The water then absorbed 2.00 × 10^9 J of heat from the Sun. What is the final temperature of the water? Assume no heat loss to the surroundings. 1/1 a) 16.9 °C b) 18.1 °C c) 17.4 °C d) 19.6 °C e) 20.2 °C

c

A wall is composed of four different materials as shown in the drawing. The wall on the right is maintained at 30.0 °C and the other wall is at 0.5 °C. The temperatures at the interfaces between the various materials are given. Rank the materials in order of largest thermal conductivity to smallest thermal conductivity. 1/1 a) A > B > C > D b) B > C > D > A c) C > B > D > A d) D > A > C > B e) C > D > A > B

c

By adding 25 kJ to solid material A, 4.0 kg will melt. By adding 50 kJ to solid material B, 6.0 kg will melt. Solid material C requires 30 kJ to melt 3.0 kg. Which of these materials, if any, has the largest value for the heat of fusion? 1/1 a) A b) B c) C d) A = B

c

Consider the system shown in the drawing. A test tube containing water is inserted into boiling water. Will the water in the test tube eventually boil? 1/1 a) Yes, heat is continually transferred to the water inside the test tube and eventually it will boil. b) Yes, the pressure above the water in the test tube will be reduced to less than atmospheric pressure and cause the water to boil. c) No, heat will only be transferred until the water in the test tube is 100 °C. d) No, the temperature of the water in the test tube will never reach 100 °C.

c

During a certain thermal process a solid object's temperature changes. Which of the following quantities is not related to the amount of the temperature change? 1/1 a) mass b) the amount of heat added or removed c) volume d) the material of which the object is composed e) the specific heat capacity

c

Four 1-kg cylinders are heated to 100 °C and placed on top of a block of paraffin wax, which melts at 63 °C. There is one cylinder made from lead, one of copper, one of aluminum, and one of iron. After a few minutes, it is observed that the cylinders have sunk into the paraffin to differing depths. Rank the depths of the cylinders from deepest to shallowest. 1/1 a) lead > iron > copper > aluminum b) aluminum > copper > lead > iron c) aluminum > iron > copper > lead d) copper > aluminum > iron > lead e) iron > copper > lead > aluminum

c

Metal pots used in cooking on top of a stove are usually very shiny on the top and sides. Which one of the following choices indicates why this is a good idea thermally? 1/1 a) The shiny parts of the pot have greater thermal conductivity. b) The shiny parts of the pot have greatly reduced losses via convection. c) The shiny parts of the pot have greatly reduced losses via radiation. d) The shiny parts of the pot have greatly reduced losses via conduction. e) The shiny parts of the pot do not allow any heat to be lost to the environment.

c

The rate of heat flow through the wall of a house does not depend on which one of the following quantities? 1/1 a) The dimensions of the wall. b) The thickness of the wall. c) The specific heat capacity of the wall. d) The temperatures outside and inside the house. e) The thermal conductivity of the wall.

c

The three objects shown have machined out of a block of brass. The cube and pyramid have sides of length L. The sphere has a radius equal to L. The three objects are all maintained at the same temperature T that is much hotter than that of the surroundings and they are sitting on a thermally insulating slab. Which object(s) exhibit(s) the greatest rate of radiative heat transfer? 1/1 Figure not drawn to scale. a) cube only b) pyramid only c) sphere only d) cube and sphere e) cube and pyramid

c

Which one of the following statements concerning emissivity is false? 1/1 a) Emissivity depends on the condition of the surface. b) Emissivity is a dimensionless quantity. c) Emissivity depends on the surface area of the object. d) The emissivity is 1.0 for a perfect absorber. e) The emissivity is 1.0 for a perfect radiator.

c

You are looking for a material that is a very good conductor of heat. Select from the following choices the best material for this purpose. 1/1 a) concrete b) lead c) copper d) air e) steel

c

A device that is to be primarily used in the desert is being designed. The user would like the side facing the sun, the front, to absorb as little heat as possible and to lose as little heat on the opposite side, the back, of the device. Two materials for these sides of the device are being recommended: (1) a dull black material and (2) a shiny, metallic material. Which of these materials should be used for the front and back sides of the device? 1/1 a) The front should be material 2 and the back should be material 1. b) The front should be material 1 and the back should be material 2. c) Both sides should be material 1. d) Both sides should be material 2. e) Using either of these materials for the front and back will have the same result.

d

Brittany's normal body temperature is 36.5 °C. When she recently became ill, her body temperature increased to 38.0 °C. What was the minimum amount of heat required for this increase in body temperature if her weight is 561 N? 1/1 a) 2.96 × 10^6 J b) 3.50 × 10^3 J c) 4.98 × 10^4 J d) 3.00 × 10^5 J e) 7.60 × 10^5 J

d

Suppose you are sitting next to a fireplace in which there is a fire burning. One end of a metal poker has been left in the fire. Which one of the following statements concerning this situation is true? 1/1 a) Heat escapes through the chimney primarily through conduction. b) The other end of the poker is warmed through convection. c) You can feel the heat of the fire primarily because of conduction. d) The other end of the poker is warmed through conduction. e) You can feel the heat of the fire primarily because of convection

d

Under which one of the following circumstances will heat transfer occur via convection? 1/1 a) Convection occurs within metal objects. b) Convection only occurs in non-metallic solids. c) Convection occurs only within a vacuum. d) Convection occurs in the presence of a liquid or a gas. e) Convection can occur whether matter is present or not.

d

What thickness of concrete, with a thermal conductivity of 1.1 W/(m▪K) will conduct heat at the same rate as 0.25 m of air, which has a thermal conductivity of 0.0256 W/(m▪K), if all other conditions are the same? 1/1 a) 8.9 m b) 4.3 m c) 1.4 m d) 11 m e) 0.25 m

d

Why is water often used as a coolant in automobiles, other than the fact that it is abundant? 1/1 a) Water expands very little as it is heated. b) The freezing temperature of water has a relatively large value. c) The specific heat of water is relatively small and its temperature can be rapidly decreased. d) The specific heat of water is relatively large and it can store a great deal of thermal energy. e) Water does not easily change into a gas.

d

During the summer, sunlight warms the land beside a cool lake. This warming is followed by a breeze blowing from the direction of the lake toward the land. Which of the following provides the best explanation for this summer breeze? 1/1 a) Air naturally flows from cooler locations to warmer locations. b) The lake must be west of the land because winds typically blow from the west. c) The land is usually cooler near a lake, so this is a case of temperature inversion which causes air to blow from the direction of the lake. d) Warm air rises above the land and cooler air moves downward, appearing to come from the direction of the lake, but it is really from above the land. e) Warm air rises from above the land and is replaced by the air blowing in from the lake.

e

Heat is added to a substance, but its temperature does not increase. Which one of the following statements provides the best explanation for this observation? 1/1 a) The substance has unusual thermal properties. b) The substance must be cooler than its environment. c) The substance must be a gas. d) The substance must be an imperfect solid. e) The substance undergoes a change of phase.

e

Heat is expressed in the same units as which one of the following quantities? 1/1 a) temperature b) power c) force/time d) specific heat capacity e) work

e

The space between the inner walls of a thermos bottle (sometimes called a Dewar flask) is evacuated to remove the air that would otherwise be there. Why is this evacuation done? 1/1 a) This is done to protect the wall of the bottle that is silvered. b) This is done to minimize heat transfer by conduction and radiation. c) This is done to increase the specific heat capacity of the bottle. e) This is done to minimize heat transfer by conduction and convection.

e

Which one of the following is not an example of convection? 1/1 a) An eagle soars on an updraft of wind. b) Spaghetti is cooked in water. c) Smoke rises above a fire. d) An electric heater warms a room. e) A person gets a suntan on a beach.

e

Which one of the following statements concerning thermal conductors is true? 1/1 a) A good thermal conductor often exhibits a very low thermal expansion coefficient. b) A good thermal conductor is often a poor electrical conductor. c) A good thermal conductor is often more likely to be a gas rather than a solid. d) A good thermal conductor often exhibits a very low specific heat capacity. e) A good thermal conductor is often also a good electrical conductor.

e