Deck 11: Energy in Thermal Processes

Question 1

On a sunny day at the beach,the reason the sand gets so hot and the water stays relatively cool is attributed to the difference in which property between water and sand?

A)mass density
B)specific heat
C)temperature
D)thermal conductivity

Answer 1

specific heat

Question 2

A 38.0-kg cheetah accelerates from rest to 26.0 m/s in 3.00 seconds. Assume the cheetah converts food energy to mechanical energy with an efficiency of 25.0%
At what average rate is the cheetah burning Calories?

A)4.09 Cal/s
B)12 840 Cal/s
C)4 280 Cal/s
D)1.023 Cal/s

Answer 2

4.09 Cal/s

Question 3

A 10.0-kg piece of aluminum (which has a specific heat of 900 J/kg⋅°C)is warmed so that its temperature increases by 6.0 C°.How much heat was transferred into it?

A)5.4E+4 J
B)9.0E-2 J
C)1.1E+4 J
D)3.7E-4 J

Answer 3

5.4E+4 J

Question 4

Heat flow occurs between two bodies in thermal contact when they differ in what property?

A)mass
B)specific heat
C)density
D)temperature

Question 5

Calories of the food type are equal to which of the following?

A)4.186 J
B)4 186 J
C)1 BTU
D)1054 J

Question 6

How many calories are equal to four BTU? (One calorie = 4.186 J,one BTU = 1 054 J. )

A)1.007
B)15.89
C)1007
D)1589

Question 7

The first experiment,which systematically demonstrated the equivalence of mechanical energy and heat,was performed by

A)Joule.
B)Boltzmann.
C)Thompson,Count Rumford.
D)Kelvin.

Question 8

Sea breezes that occur near the shore are attributed to a difference between land and water with respect to what property?

A)mass density
B)coefficient of volume expansion
C)specific heat
D)emissivity

Question 9

If a 1 050-kg car was moving at 25 m/s,what would be its kinetic energy expressed in the unusual (for kinetic energy)units of calories? (1 cal = 4.186 J)

A)3.1E+5
B)3.3E+5
C)6.6E+5
D)7.8E+4
E)6.3E+3

Question 10

An inventor develops a stationary cycling device by which an individual,while pedaling,can convert all of the energy expended into heat for warming water.How much mechanical energy is required to increase the temperature of 200 g of water (enough for 1 cup of coffee)from 18°C to 94°C? (1 cal = 4.186 J,the specific heat of water is 4 186 J/kg⋅°C)​

A)6.4E+4 J
B)3.2E+4 J
C)1.6E+4 J
D)1.0E+3 J
E)​1.5E+1 J

Question 11

Arrange from smallest to largest: the BTU,the joule,and the calorie.

A)BTU,J,cal
B)J,cal,BTU
C)cal,BTU,J
D)J,BTU,cal

Question 12

As I use sandpaper on some rusty metal,the sandpaper gets hot because:

A)heat is flowing from the sandpaper into the metal.
B)heat is flowing from the metal into the sandpaper.
C)frictional processes increase the internal energy of the sandpaper.
D)heat is flowing from my hand into the sandpaper.

Question 13

Which of the following statements is true?

A)A hot object contains a lot of heat.
B)A cold object contains only a little heat.
C)Objects do not contain heat.
D)Statements a and b are true.

Question 14

If heat is flowing from a table to a block of ice moving across the table,which of the following must be true?

A)The table is rough and there is friction between the table and ice.
B)The ice is cooler than the table.
C)The ice is changing phase.
D)All three are possible,but none is absolutely necessary.

Question 15

Marc attaches a falling 328-kg object with a rope through a pulley to a paddle wheel shaft.He places the system in a well-insulated tank holding 23.2 kg of water.When the object falls,it causes the paddle wheel to rotate and churn the water.If the object falls a vertical distance of 88.6 m at constant speed,what is the temperature change of the water? (1 kcal = 4 186 J,the specific heat of water is 4 186 J/kg⋅°C,and g = 9.80 m/s²)

A)17 000 C°
B)2 930 C°
C)2.93 C°
D)0.587 C°
E)5.87 C°

Question 16

A 38.0-kg cheetah accelerates from rest to 26.0 m/s in 3.00 seconds. Assume the cheetah converts food energy to mechanical energy with an efficiency of 25.0%
What is the maximum rate at which the cheetah is burning Calories?

A)2.05 Cal/s
B)8 560 Cal/s
C)8.18 Cal/s
D)6 420 Cal/s

Question 17

An inventor develops a stationary cycling device by which an individual,while pedaling,can convert all of the energy expended into heat for warming water.What minimum power must be generated if 210 g water (enough for 1 cup of coffee)is to be heated in 14.0 min from 26.0°C to 84.0°C? (1 cal = 4.186 J,the specific heat of water is 4 186 J/kg⋅°C)

A)3 640 W
B)289 W
C)60.7 W
D)850 W
E)42.5 W

Question 18

​A typical avocado has 180 Calories.If all this energy could be used to lift a bucket of water weighing 40 N,through what vertical distance could the bucket be lifted? (1 calorie = 4.184 J and 1 Calorie = 10³ calories)

A)1.72E+6 m
B)3.01E+7 m
C)​7.53E+5 m
D)1.88E+4 m

Question 19

Who demonstrated that when heat is gained or lost by a system during some process,the gain or loss can be accounted for by an equivalent quantity of mechanical work done on the system?

A)Joule
B)Boltzmann
C)Thompson,Count Rumford
D)Kelvin

Question 20

Of the following systems,which contains the most heat?

A)100 kg of water at 80°C
B)250 kg of water at 40°C
C)600 kg of ice at 0°C
D)Systems do not contain heat.

Question 21

In typical calorimetry problems,what is the usual conservation law being used?

A)energy
B)heat
C)temperature
D)None since nothing is being conserved.

Question 22

A swimming pool heater has to be able to raise the temperature of the 50 000 gallons of water in the pool by 12.0 C°.How many kilowatt-hours of energy are required? (One gallon of water has a mass of approximately 3.8 kg and the specific heat of water is 4,186 J/kg⋅°C. )

A)6.98E+2 kWh
B)2.65E+3 kWh
C)2.21E+2 kWh
D)2.65E+4 kWh
E)2.65E+2 kWh

Question 23

A 3.00-kg copper rod is 45.0 cm long at 24.8°C.If 45 000 J are transferred to the rod by heat,what is its change in length? c_copper = 387 J/kg⋅°C and α_copper = 17.0 × 10−⁶/°C.

A)34.4 cm
B)0.0297 cm
C)0.133 cm
D)0.0445 cm
E)More information is needed.

Question 24

Twenty grams of a solid at 70°C is place in 100 grams of a fluid at 20°C.Thermal equilibrium is reached at 30°C.The specific heat of the solid

A)is equal to that of the fluid.
B)is less than that of the fluid.
C)is more than that of the fluid.
D)cannot be compared to that of a material in a different phase.

Question 25

Which of the following has the highest specific heat?

A)ice
B)water
C)steam
D)They are all water,so they all have the same specific heat.

Question 26

What is the temperature increase of 3.00 kg of water when heated by a 900-W immersion heater for 9.00 min? (c_w = 4 186 J/kg⋅°C)

A)77.4°C
B)48.4°C
C)38.7°C
D)19.4°C
E)0.645°C

Question 27

A slice of bread contains about 125 kcal.If specific heat of a person were 1.00 kcal/kg⋅°C,by how many °C would the temperature of a 65.0-kg person increase if all the energy in the bread were converted to heat?

A)3.85°C
B)0.96°C
C)1.92°C
D)2.40°C
E)1.44°C

Question 28

A piece of copper of mass 110 g is being drilled through with a ¹/₂" electric drill.The drill operates at 25.0 W and takes 25.0 s to bore through the copper.If all the energy from the drill heats the copper,find the copper's increase in temperature.c_copper = 387 J/kg⋅°C.

A)18.4 C°
B)23.5 C°
C)14.7 C°
D)22.0 C°
E)29.4 C°

Question 29

A solar heating system has a 25.0% conversion efficiency;the solar radiation incident on the panels is 800 W/m².What is the increase in temperature of 25.0 kg of water in a 1.00-h period by a 3.40-m²-area collector? (c_w = 4 186 J/kg⋅°C)

A)93.6°C
B)6.88°C
C)23.4°C
D)46.8°C
E)17.5°C

Question 30

A 0.200-kg aluminum plate,initially at 20°C,slides down a 13.0-m-long surface,inclined at a 25.0° angle to the horizontal.The force of kinetic friction exactly balances the component of gravity down the plane so that the plate,once started,glides down at constant velocity.If 90% of the mechanical energy of the system is absorbed by the aluminum,what is its temperature increase at the bottom of the incline? (Specific heat for aluminum is 900 J/kg⋅°C. )

A)0.115 C°
B)0.0538 C°
C)0.269 C°
D)0.78 C°
E)48.5 C°

Question 31

A 4.00-g lead bullet is traveling at a speed of 200 m/s when it embeds in a wood post.If we assume that half of the resultant heat energy generated remains with the bullet,what is the increase in temperature of the embedded bullet? (specific heat of lead = 0.0305 kcal/kg⋅°C,1 kcal = 4 186 J)

A)78.3 °C
B)157 °C
C)313 °C
D)39.2 °C
E)97.9 °C

Question 32

A machine gear consists of 0.14 kg of iron and 0.19 kg of copper.How much total heat is generated in the part if its temperature increases by 35.0 C°? (Specific heats of iron and copper are 450 and 390 J/kg⋅°C,respectively. )

A)4.5E+3 J
B)4.8E+3 J
C)5.2E+3 J
D)2.2E+3 J
E)2.6E+3 J

Question 33

In the text there is a table of coefficients of linear (α)and volume (β)expansions due to temperature changes.For the solid materials in this list,there is a relationship between α and β which allows you to find the value of β if you know α.Which of the following best describes that relationship?

A)α = β³
B)3α = β
C)α = 3β
D)α³ = β

Question 34

A waterfall is 128 m high.What is the increase in water temperature at the bottom of the falls if all the initial potential energy goes into heating the water? (g = 9.8 m/s²,c_w = 4 186 J/kg⋅°C)

A)0.15°C
B)0.30°C
C)0.90°C
D)0.37°C
E)0.60°C

Question 35

A solar heated house loses about 5.5 × 10⁷ cal through its outer surfaces on a typical 24-h winter day.What mass of storage rock is needed to provide this amount of heat if it is brought up to initial temperature of 58°C by the solar collectors and the house is maintained at 23°C? (Specific heat of rock is 0.21 cal/g⋅°C. )

A)1.4E+3 kg
B)7.5E+4 kg
C)7.5E+3 kg
D)7.5E+2 kg
E)1.6E+3 kg

Question 36

A hot (85.0°C)lump of metal has a mass of 210 g and a specific heat of 0.250 cal/g⋅°C.John drops the metal into a 345-g calorimeter containing 95 g of water at 21.3°C.The calorimeter is constructed of a material that has a specific heat of 0.100 cal/ g⋅°C.When equilibrium is reached,what will be the final temperature? c_water = 1.00 cal/g⋅°C.

A)35.6°C
B)63.9°C
C)49.6°C
D)39.7°C
E)29.4°C

Question 37

Find the final equilibrium temperature when 20.0 g of milk at 15.0°C is added to 155.0 g of coffee at 89.0°C.(Assume the specific heats of coffee and milk are the same as water and neglect the heat capacity of the container. )c_water = 1.00 cal/g⋅°C = 4 186 J/kg⋅°C

A)80.5°C
B)100°C
C)104°C
D)77.1°C
E)78.9°C

Question 38

Pennies used to be made of copper,but now they are made of copper-coated zinc.If one were to do a precise calorimetry experiment to determine the specific heat of the new pennies,what would the result be?

A)It would be that of copper since copper is on the outside.
B)It would be that of zinc since zinc is in the center.
C)It would be the sum of the copper and zinc specific heats.
D)It would be between that of copper and that of zinc,depending on coating thickness.

Question 39

A 140-g block of copper is taken from a kiln and quickly placed into a beaker of negligible heat capacity containing 290 g of water.The water temperature rises from 6.8°C to 26.8°C.Given c_Cu = 0.10 cal/g⋅°C,and c_water = 1.00 cal/g⋅°C,what was the temperature of the kiln?

A)720°C
B)387°C
C)682°C
D)441°C
E)68.2°C

Question 40

A plot of the temperature versus the energy per kg added to a piece of ice as it goes from below freezing at −10°C to becoming steam at 110°C consists of straight lines,some horizontal and some with an upward slope.What do the upward slopes represent?

A)specific heats
B)reciprocals of specific heats
C)latent heats
D)reciprocals of latent heats

Question 41

Suppose working outside on a hot day someone generate 450 J of heat each second.If this energy is compensated for by the evaporation of sweat,how much water would be lost in an hour? The latent heat of fusion for water is 334 kJ/kg and for vaporization is 2 200 kJ/kg.

A)4.9 liter
B)0.74 liter
C)0.50 liter
D)1.5 liter

Question 42

I take 2.0 kg of ice and dump it into 2.3 kg of water and,when equilibrium is reached,I have 4.3 kg of ice at 0°C.The water was originally at 0°C.The specific heat of water = 1.00 kcal/kg⋅°C,the specific heat of ice = 0.500 kcal/kg⋅°C,and the latent heat of fusion of water is 80.0 kcal/kg.The original temperature of the ice was

A)one or two degrees below 0°C.
B)-46.0°C.
C)-184°C.
D)184°C.
E)The whole experiment is impossible.

Question 43

Carly places one end of a steel bar in a Bunsen flame and the other end in an ice cube.By what factor is the rate of heat flow changed when the bar's cross-sectional area is doubled?

A)2
B)1/2
C)4.0
D)1/4

Question 44

Iced tea is made by adding ice to 1.9 kg of hot tea,initially at 90.0°C.How many kg of ice,initially at 0°C,are required to bring the mixture to 15.0°C? (L_f = 3.33 × 10⁵ J/kg,c_w = 4 186 J/kg⋅°C)

A)1.6 kg
B)2.1 kg
C)1.5 kg
D)3.1 kg
E)1.7 kg

Question 45

In cloud formation,water vapor turns into water droplets which get bigger and bigger until it rains.This will cause the temperature of the air in the clouds to

A)get warmer.
B)get cooler.
C)will not affect the temperature of the air in the clouds.
D)There is no air in clouds.

Question 46

Which of the following best describes a substance in which the temperature remains constant while at the same time it is experiencing an inward heat flow?

A)gas
B)liquid
C)solid
D)substance undergoing a change of state

Question 47

Which of the following involves the greatest heat transfer?

A)One gram of steam at 100°C changing to water at 100°C.
B)One gram of ice at 0°C changing to water at 0°C.
C)One gram of water cooling from 100°C to 0°C.
D)One gram of ice heating from −100°C to 0°C.

Question 48

A puddle holds 160.0 g of water.If 0.5 g of water evaporates from the surface,what is the approximate temperature change of the remaining water? (L_v = 540 cal/g)

A)+1.7 C°
B)−1.7 C°
C)+0.17 C°
D)−0.17 C°

Question 49

Dmitri places one end of a copper rod in a heat reservoir and the other end in a heat sink.By what factor is the rate of heat flow changed when the temperature difference between the reservoir and sink is tripled?

A)0.33
B)1/9
C)3.0
D)9.0

Question 50

When heating 2 kg of ice from -40°C,2 kg of water from 20°C to 50°C,and 2 kg of steam from 100°C to 125°C,which requires the most energy?

A)the ice
B)the water
C)The steam,it's obvious since it is the hottest.
D)All three take the same amount.

Question 51

125 g of dry ice (solid CO₂)is dropped into a beaker containing 600 g of 64.0°C water.The dry ice converts directly to gas,leaving the solution.When the dry ice is gone,the final temperature of the water is 33.2°C.What is the heat of vaporization of solid CO₂? (c_water = 1.00 cal/g⋅°C)

A)160 cal/g
B)142 cal/g
C)118 cal/g
D)148 cal/g
E)154 cal/g

Question 52

How much heat energy must be removed from 250 g of oxygen at 21.0°C to liquefy it at −183°C? (The specific heat of oxygen gas is 0.218 cal/g⋅°C,and its heat of vaporization is 50.9 cal/g. )

A)4.8E+4 cal
B)2.4E+4 cal
C)6.0E+3 cal
D)1.2E+4 cal
E)3.6E+4 cal

Question 53

Two stars,A and B,have the same emissivity,but the radii and surface temperatures are different with R_A = 0.5R_B,and T_A = 2T_B.Assuming the temperature of space to be negligible,which star radiates the most energy per unit time?

A)Star A
B)Star B
C)Both radiate the same amount of energy per unit time.
D)More information is needed in order to make a determination.

Question 54

A blacksmith drops a 550 ^$\circ$ F piece of iron into a vat of 75 ^$\circ$ F water in order to cool it to 100 ^$\circ$ F.How many kilograms of water are needed per kilogram of iron? Assume all the thermal energy from the iron is transferred to the water and none of the water evaporates.The specific heats of water and iron are 4186 J/kg ^$\circ$ C and 448 J/kg ^$\circ$ C,respectively.

A)9.3 kg
B)0.78 kg
C)0.52 kg
D)1.9 kg

Question 55

Two 0.95-kg masses,one aluminum and one tin,both at 80.0 ^$\circ$ C,are placed in 1.00 kg of water at 20.0 ^$\circ$ C.What is the equilibrium temperature of the system? The specific heats of aluminum and tin are 900 J/kg ^$\circ$ C and 227 J/kg ^$\circ$ C,respectively.

A)32.2 ^$\circ$ C
B)27.1 ^$\circ$ C
C)13.2 ^$\circ$ C
D)40.3 ^$\circ$ C

Question 56

A 5.0-g lead bullet traveling in 19.0°C air at 300 m/s strikes a flat steel plate and stops.What is the final temperature of the lead bullet? (Assume the bullet retains all heat. )The melting point of lead is 327°C.The specific heat of lead is 0.128 J/g⋅°C.The heat of fusion of lead is 24.5 J/g.

A)278°C
B)186°C
C)445°C
D)327°C
E)371°C

Question 57

A 0.0040-kg lead bullet is traveling at a speed of 220 m/s when it embeds in a block of ice at 0°C.If all the heat generated goes into melting ice,what quantity of ice is melted? (L_f = 80 kcal/kg,the specific heat of lead = 0.03 kcal/kg⋅°C,and 1 kcal = 4 186 J)

A)1.6E-2 kg
B)5.8E-4 kg
C)4.6E-3 kg
D)2.9E-4 kg
E)1.9E-5 kg

Question 58

150 g of liquid nitrogen at its boiling point of 77.0 K is stirred into a beaker containing 510 g of 18.0°C water.If the nitrogen leaves the solution as soon as it turns to gas,how much water freezes? The heat of vaporization of nitrogen is 48.0 cal/g and that of water is 80.0 cal/g.

A)none
B)21 g
C)42 g
D)11 g
E)63 g

Question 59

How much heat energy is required to vaporize a 4.40-g ice cube at 0°C? The heat of fusion of ice is 80.0 cal/g.The heat of vaporization of water is 540 cal/g,and c_water = 1.00 cal/g⋅°C.

A)2 730 cal
B)3 170 cal
C)2 820 cal
D)3 520 cal
E)2 380 cal

Question 60

A 35.0-g cube of ice,initially at 0.0°C,is dropped into 180.0 g of water in an 70.0-g aluminum container,both initially at 35.0°C.What is the final equilibrium temperature? (Specific heat for aluminum is 900 J/kg⋅°C,the specific heat of water is 4 186 J/kg⋅°C,and L_f = 3.33 × 10⁵ J/kg. )

A)35.1°C
B)17.6°C
C)8.79°C
D)26.4°C
E)30.8°C

Question 61

The thermal conductivity of copper is 397 J/s⋅m⋅°C and of silver is 427 J/s⋅m⋅°C.A rod of each material is used as a heat conductor.If the rods have the same geometry and are used between the same temperature differences for the same time interval,what is the ratio of the heat transferred by copper to the heat transferred by the silver?

A)0.930
B)1.395
C)2.093
D)0.465
E)0.791

Question 62

The emissivity of an ideal reflector has which of the following values?

A)0
B)1
C)100
D)infinity

Question 63

Which one of the following processes of heat transfer requires the presence of a fluid?

A)conduction
B)radiation
C)convection
D)none of the above choices are valid

Question 64

An object at 30.0°C has its temperature increased to 41.0°C.The power then radiated by this object increases by how many percent?

A)10.0
B)15.3
C)3.63
D)36.7
E)96.5

Question 65

The filament temperature of a light bulb is 2 100 K when the bulb delivers 40.0 W of power.If its emissivity remains constant,what power is delivered when the filament temperature is 2 500 K?

A)161 W
B)121 W
C)80.3 W
D)60.3 W
E)40.2 W

Question 66

Consider two different rods.The greatest thermal conductivity will be in the rod with

A)electrons that are freer to move from atom to atom.
B)the greater specific heat.
C)the greater cross-sectional area.
D)the greater length.

Question 67

At high noon,the Sun delivers 990 W to each square meter of a blacktop road.What is the equilibrium temperature of the hot asphalt,assuming its emissivity e = 1? (σ = 5.67 × 10−⁸ W/m²⋅K⁴).

A)364°C
B)637°C
C)90.5°C
D)181°C
E)136°C

Question 68

If one's hands are being warmed by holding them to one side of a flame,the predominant form of heat transfer is what process?

A)conduction
B)radiation
C)convection
D)vaporization

Question 69

In winter,light-colored clothes will keep you warmer than dark-colored clothes if

A)you are warmer than your surroundings.
B)you are at the same temperature as your surroundings.
C)you are cooler than your surroundings.
D)you are standing in sunlight.

Question 70

If cooking is done using an aluminum pan over an electric burner,which of the following will not promote the rate of heat flow from burner to food?

A)increase pan bottom thickness
B)increase pan bottom area
C)increase burner temperature
D)decrease height of pan sides

Question 71

The surface of the Sun has a temperature of about 5 770 K.If the radius of the Sun is 7 × 10⁸ m,determine the power output of the Sun.(Take e = 1,and σ = 5.67 × 10−⁸ W/m²⋅K⁴).

A)3.9E+26 W
B)1.2E+26 W
C)6.7E+22 W
D)2.2E+30 W
E)5.5E+17 W

Question 72

The use of fiberglass insulation in the outer walls of a building is intended to minimize heat transfer through the wall by what process?

A)conduction
B)radiation
C)convection
D)vaporization

Question 73

Which type of heating causes sunburn?

A)conduction
B)convection
C)radiation
D)all of the above

Question 74

A silver bar of length 25.0 cm and cross-sectional area 1.25 cm² is used to transfer heat from a 80.5°C reservoir to a 0°C block of ice.How much ice is melted per second? (For silver,k = 427 J/s⋅m⋅°C.For ice,L_f = 334 000 J/kg. )

A)0.515 g/s
B)1.29 g/s
C)0.00515 g/s
D)0.0515 g/s
E)5.15 g/s

Question 75

A windowpane is half a centimeter thick and has an area of 1.10 m².The temperature difference between the inside and outside surfaces of the pane is 19.0 °C.What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.840 J/s⋅m⋅°C. )

A)7 020 J/s
B)3 510 J/s
C)4 180 J/s
D)1 850 J/s
E)2 200 J/s

Question 76

The tungsten filament of a light bulb has an operating temperature of about 2 050 K.If the emitting area of the filament is 0.70 cm²,and its emissivity is 0.68,what is the power output of the light bulb? (σ = 5.67 × 10−⁸ W/m²⋅K⁴)

A)70.1 W
B)47.7 W
C)477 W
D)42.7 W
E)39.7 W

Question 77

The surfaces of a Dewar flask are silvered for the purpose of minimizing heat transfer by what process?

A)conduction
B)radiation
C)convection
D)vaporization

Question 78

A 1.9-m² Thermopane window is constructed by using two layers of glass 4.0 mm thick,separated by an air space of 5.0 mm.If the temperature difference is 25.0 °C from the inside of the house to the outside air,what is the rate of heat flow through this window? (Thermal conductivity for glass is 0.840 J/s⋅m⋅°C and for air 0.023 4 J/s⋅m⋅°C. )

A)2 530 W
B)426 W
C)3 190 W
D)210 W
E)2 100

Question 79

When a wool blanket is used to keep warm,what is the primary insulating material?

A)wool
B)air
C)the trim around the edge of the blanket
D)a thin layer of aluminum foil (usually not apparent)inside the blanket

Question 80

How does the heat energy from the Sun reach us through the vacuum of space?

A)conduction
B)radiation
C)convection
D)none of the above choices are valid