Question 1

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?

Accepted Answer

The rate of heat flow is directly proportional to the temperature difference between the reservoir and sink. When the temperature difference is tripled, the rate of heat flow is also tripled. Therefore, the factor by which the rate of heat flow changes is 3.0.

Question 2

Which of the following involves the greatest heat transfer?

Accepted Answer

The greatest heat transfer occurs when 1 gram of steam at 100°C changes to water at 100°C because it involves both the heat of vaporization and the heat of fusion, which have the highest heat transfer values per unit mass. Option B involves the heat of fusion, but the temperature does not change, so the heat transfer is lower. Option C involves only a decrease in temperature and option D involves only an increase in temperature, so their heat transfer values are lower than option A.

Question 3

A windowpane is half a centimeter thick and has an area of 0.9 m².The temperature difference between the inside and outside surfaces of the pane is 14 °C.What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/s⋅m⋅°C. )

Accepted Answer

The rate of heat flow (Q/t) through a material is given by the formula: Q/t = (k * A * ΔT) / d, where k is the thermal conductivity, A is the area, ΔT is the temperature difference, and d is the thickness. Substituting the given values: Q/t = (0.84 J/s⋅m⋅°C * 0.9 m² * 14 °C) / 0.005 m = 2,100 J/s.

Question 4

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

Accepted Answer

The silvered surfaces are designed to reflect thermal radiation, which is the transfer of heat energy through electromagnetic waves, and thus minimize heat transfer. Conduction, convection, and vaporization are not directly affected by the silvered surface.

Question 5

How much heat energy must be removed from 150 g of oxygen at 21°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. )
​

Accepted Answer

The answer of How much heat energy must be removed...

Question 6

A 1.8-m² Thermopane window is constructed,using two layers of glass 5.0 mm thick,separated by an air space of 6.0 mm.If the temperature difference is 22 °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 0.84 J/s⋅m⋅°C and for air 0.023 4 J/s⋅m⋅°C. )

Accepted Answer

The answer of A 1.8-m² Thermopane window is constructed,using two...

Question 7

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

Accepted Answer

Air is considered the primary insulating material in a wool blanket. Wool fibers trap air within them, creating pockets of insulation that help to retain body heat. The trim around the edge of the blanket and a thin layer of aluminum foil inside the blanket are not typically used as insulating materials in wool blankets.

Question 8

A 3-g lead bullet traveling in 21°C air at 295 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.
​

Accepted Answer

The answer of A 3-g lead bullet traveling in 21°C...

Question 9

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?

Accepted Answer

Increasing the thickness of the pan bottom would actually reduce the rate of heat flow from the burner to the food because thicker materials tend to have higher thermal resistance, making it harder for heat to pass through quickly.

Question 10

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

Accepted Answer

An ideal reflector would reflect all incident radiation, thus it would have an emissivity of 0.

Question 11

140 g of liquid nitrogen at its boiling point of 77 K is stirred into a beaker containing 510 g of 16°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 cal/g and that of water is 80 cal/g.

Accepted Answer

The answer of 140 g of liquid nitrogen at its...

Question 12

The thermal conductivity of silver is 427 J/s⋅m⋅°C and of copper is 397 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 silver to the heat transferred by the copper?

Accepted Answer

The ratio of the heat transferred by silver to copper is the ratio of their thermal conductivities, which is 427/397 = 1.076.

Question 13

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?

Accepted Answer

The rate of heat flow is directly proportional to the cross-sectional area of the steel bar. Therefore, doubling the cross-sectional area would double the rate of heat flow. Hence, the factor by which the rate of heat flow is changed is 2.

Question 14

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?

Accepted Answer

When hands are being warmed by holding them to one side of a flame, the predominant form of heat transfer is radiation. In radiative heat transfer, heat is transferred through the emission of electromagnetic waves by one surface and can be absorbed by another surface.

Question 15

The filament temperature of a light bulb is 2,000 K when the bulb delivers 40 W of power.If its emissivity remains constant,what power is delivered when the filament temperature is 2,400 K?
​

Accepted Answer

The power radiated by an object is given by the Stefan-Boltzmann law:

P = εσAT^4

where P is the power radiated, ε is the emissivity, σ is the Stefan-Boltzmann constant (5.67 x 10^-8 W/m^2/K^4), A is the surface area of the object, and T is the temperature in Kelvin.

Since the emissivity remains constant, we can write:

P1/P2 = (T1/T2)^4

where P1 is the power when T1 = 2,000 K, and P2 is the power when T2 = 2,400 K.

Plugging in the values and solving for P2, we get:

P2 = P1 (T2/T1)^4 
    = 40 W (2.4/2)^4 
    ≈ 83 W

Therefore, the answer is C.

Question 16

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

Accepted Answer

Heat energy from the sun reaches us through the vacuum of space through radiation. Radiation is the transfer of energy through electromagnetic waves, such as visible light and infrared radiation. This allows the heat energy to travel through space and reach Earth without the need for a medium, such as air or water, to conduct or convect the energy.

Question 17

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

Accepted Answer

Convection is the process of heat transfer that involves the movement of fluids, such as air or water, in response to temperature differences. Without the presence of a fluid, convection cannot occur. Conduction involves the transfer of heat through a solid material, while radiation involves the transfer of heat through electromagnetic waves and does not require the presence of a medium.

Question 18

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

Accepted Answer

Fiberglass insulation works by reducing heat transfer through conduction, which is the process by which heat moves through a material from a higher temperature to a lower temperature. The small fiberglass fibers in the insulation trap air pockets, which slows down the movement of heat through the wall, thereby reducing heat loss in the winter and heat gain in the summer. Fiberglass insulation does not typically address radiation, convection, or vaporization.

Question 19

How much heat energy is required to vaporize a 1.0-g ice cube at 0°C? The heat of fusion of ice is 80 cal/g.The heat of vaporization of water is 540 cal/g,and c_water = 1.00 cal/g⋅°C.

Accepted Answer

To solve for the total heat energy required to vaporize the ice cube, we need to follow these steps:
1. First, we need to determine the amount of heat energy required to melt the ice cube. Using the heat of fusion of ice, we can calculate this as:
q1 = m ∙ ΔHfus = 1.0 g ∙ 80 cal/g = 80 cal
2. Next, we need to determine the amount of heat energy required to raise the temperature of the melted ice to its boiling point. Since the ice is at 0°C, we need to raise its temperature to 100°C (the boiling point of water). Using the specific heat capacity of water, we can calculate this as:
q2 = m ∙ c ∙ ΔT = 1.0 g ∙ 1.00 cal/g⋅°C ∙ (100°C - 0°C) = 100 cal
3. Finally, we need to determine the amount of heat energy required to vaporize the water. Using the heat of vaporization of water, we can calculate this as:
q3 = m ∙ ΔHvap = 1.0 g ∙ 540 cal/g = 540 cal
4. The total heat energy required is the sum of q1, q2, and q3:
qtotal = q1 + q2 + q3 = 80 cal + 100 cal + 540 cal = 720 cal
Therefore, the best choice is B.

Question 20

I take 0.9 kg of ice and dump it into 0.9 kg of water and,when equilibrium is reached,I have 1.8 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 = 0.50 kcal/kg⋅°C,and the latent heat of fusion of water is 80 kcal/kg.The original temperature of the ice was:

Accepted Answer

The original temperature of the ice was -160°C. The heat gained by the ice to reach 0°C and then freeze the water equals the heat lost by the water. Solving the energy balance equation gives the initial temperature of the ice as -160°C.

Quiz 11: Energy in Thermal Processes Heat and Internal Energy

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?

Which of the following involves the greatest heat transfer?

A windowpane is half a centimeter thick and has an area of 0.9 m².The temperature difference between the inside and outside surfaces of the pane is 14 °C.What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/s⋅m⋅°C. )

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

How much heat energy must be removed from 150 g of oxygen at 21°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. )

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

A 3-g lead bullet traveling in 21°C air at 295 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.

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?

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

140 g of liquid nitrogen at its boiling point of 77 K is stirred into a beaker containing 510 g of 16°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 cal/g and that of water is 80 cal/g.

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?

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?

The filament temperature of a light bulb is 2,000 K when the bulb delivers 40 W of power.If its emissivity remains constant,what power is delivered when the filament temperature is 2,400 K?

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

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

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

How much heat energy is required to vaporize a 1.0-g ice cube at 0°C? The heat of fusion of ice is 80 cal/g.The heat of vaporization of water is 540 cal/g,and c_water = 1.00 cal/g⋅°C.

Quiz 11: Energy in Thermal Processes Heat and Internal Energy

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?

Which of the following involves the greatest heat transfer?

A windowpane is half a centimeter thick and has an area of 0.9 m2.The temperature difference between the inside and outside surfaces of the pane is 14 °C.What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/s⋅m⋅°C. ) ​

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

How much heat energy must be removed from 150 g of oxygen at 21°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. ) ​

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

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?

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

140 g of liquid nitrogen at its boiling point of 77 K is stirred into a beaker containing 510 g of 16°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 cal/g and that of water is 80 cal/g.

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?

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?

The filament temperature of a light bulb is 2,000 K when the bulb delivers 40 W of power.If its emissivity remains constant,what power is delivered when the filament temperature is 2,400 K? ​

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

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

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

How much heat energy is required to vaporize a 1.0-g ice cube at 0°C? The heat of fusion of ice is 80 cal/g.The heat of vaporization of water is 540 cal/g,and cwater = 1.00 cal/g⋅°C.

A windowpane is half a centimeter thick and has an area of 0.9 m².The temperature difference between the inside and outside surfaces of the pane is 14 °C.What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/s⋅m⋅°C. )

How much heat energy must be removed from 150 g of oxygen at 21°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. )

The filament temperature of a light bulb is 2,000 K when the bulb delivers 40 W of power.If its emissivity remains constant,what power is delivered when the filament temperature is 2,400 K?

How much heat energy is required to vaporize a 1.0-g ice cube at 0°C? The heat of fusion of ice is 80 cal/g.The heat of vaporization of water is 540 cal/g,and c_water = 1.00 cal/g⋅°C.