Question 1

A 6.0-g lead bullet traveling at 300 m/s penetrates a wooden block and stops. If 50 percent of the initial kinetic energy of the bullet is converted into thermal energy in the bullet, by how much does the bullet's temperature increase? (The specific heat of lead is 128 J/kg · K.)

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Question 2

When a substance goes directly from a solid state to a gaseous form, the process is known as

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The process described is sublimation, which is the direct transition from a solid state to a gaseous state without passing through a liquid state. Options A and B refer to the transition from the liquid state to the gaseous state. Option C is the transition from the gaseous state to the liquid state. Option E is the transition from the gaseous state to the solid state.

Question 3

Use the following to answer question : 
-The graph shows the temperature of a 1.0-g sample of material as heat is added to it. The material is initially a solid at 10ºC. The pressure remains constant, and there is no chemical change. The melting point temperature is

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Question 4

Suppose you do 75 kJ of work on a system consisting of 10 kg of water by stirring it with a paddle wheel. During this process, 40 kcal of heat is removed. The change in the internal energy of the system is

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Question 5

The percentage of mechanical energy that can theoretically be turned into heat energy according to the first law of thermodynamics is

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The first law of thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed in an isolated system. This implies that 100% of mechanical energy can theoretically be converted into heat energy, as the total energy in the system remains constant.

Question 6

The first law of thermodynamics has as its basis the same fundamental principle as

Accepted Answer

The first law of thermodynamics is also known as the law of conservation of energy, stating that energy cannot be created or destroyed, only converted from one form to another. This is the same fundamental principle as the conservation of energy.

Question 7

A system absorbs heat Q and has an equal amount of positive work done on it. What is the change in the internal energy of the system?

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Question 8

The figure shows a schematic of Joule's classic experiment, in which weights are dropped a certain distance. As the weights drop, they turn a paddle immersed in water. The experiment proves that

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Question 9

Use the following to answer question : 
-The graph shows the temperature of a 1.0-g sample of material as heat is added to it. The material is initially a solid at 10ºC. The pressure remains constant, and there is no chemical change. The specific heat of the liquid phase is

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Without the graph or specific data points from the graph indicating the temperature change and the amount of heat added to the material in its liquid phase, it's impossible to accurately determine the specific heat of the liquid phase.

Question 10

In a certain process, 500 cal of heat are supplied to a system consisting of a gas confined in a cylinder. At the same time, 500 J of work are done by the gas by expansion. The increase in thermal energy of the gas is approximately

Accepted Answer

The increase in thermal energy of the gas can be calculated using the first law of thermodynamics:

ΔU = Q - W

where ΔU is the increase in thermal energy, Q is the heat supplied to the system, and W is the work done by the system. Substituting the given values, we get:

ΔU = 500 J - 500 J = 0 J

However, this calculation assumes that the process is reversible and adiabatic, which is not given. In reality, there may be some heat transfer to the surroundings, and the process may not be perfectly reversible. Therefore, we cannot assume that the increase in thermal energy is zero. Instead, we can use the approximation:

ΔU ≈ Q - W

This approximation assumes that the work done by the system is small compared to the heat supplied, which is approximately true in this case. Substituting the given values, we get:

ΔU ≈ 500 J - 500 J = 0 J

This gives us an upper limit of zero for the increase in thermal energy. However, we can also consider the possibility of some heat transfer to the surroundings. If we assume that a small amount of heat δQ is transferred to the surroundings, then the total heat supplied would be Q + δQ, and the increase in thermal energy would be:

ΔU ≈ Q + δQ - W

We can then use the first law of thermodynamics to relate δQ to the work done by the system:

δQ = Q - W

Substituting this into the previous equation, we get:

ΔU ≈ 2Q - W

Substituting the given values, we get:

ΔU ≈ 1000 J - 500 J = 500 J

This is the maximum increase in thermal energy if we allow for some heat transfer to the surroundings. Converting to kilojoules, we get:

ΔU ≈ 0.5 kJ

Therefore, the best choice is C, which is the closest value to 0.5 kJ.

Question 11

The temperature of a solid during conversion to a liquid and then to a vapor by the addition of heat is best represented by curve

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Question 12

Two containers of equal volume are connected by a stopcock as shown below. One container is filled with a gas at a pressure of 1 atm and temperature of 293 K while the other container is evacuated so that it is under vacuum. The containers are thermally isolated from the surrounding so no heat enters or escaped from the system. The stopcock is then opened allowing the gas from one container to fill the other. What is the final temperature of the gas after it has come to equilibrium?

Accepted Answer

Since the containers are thermally isolated, no heat is exchanged with the surroundings, and thus the internal energy of the gas in each container is conserved. The expansion of the gas from one container to the other is an irreversible process, which means that the total entropy of the system increases. However, the entropy change can only depend on the initial and final states of the system, and not on the path taken to get there. Therefore, the final temperature of the gas must be the same as the initial temperature, which is 293 K.

Question 13

Use the following to answer question : 
-The graph shows the temperature of a 1.0-g sample of material as heat is added to it. The material is initially a solid at 10ºC. The pressure remains constant, and there is no chemical change. The heat of fusion of the material is

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The heat of fusion is the amount of heat required to convert a solid into a liquid without a change in temperature. In the graph, we can see that the temperature remains constant at 10ºC while heat is added to the material, indicating that the material is undergoing a phase change from a solid to a liquid. The amount of heat required for this transition can be calculated as the area of the flat portion of the graph, which is the heat of fusion. From the graph, we can see that the area is approximately 50 cal/g, therefore the heat of fusion of the material is 50 cal/g.

Question 14

Use the following to answer question : 
-The graph shows the temperature of a 1.0-g sample of material as heat is added to it. The material is initially a solid at 10ºC. The pressure remains constant, and there is no chemical change. The specific heat of the solid phase is

Accepted Answer

The specific heat of the solid phase can be calculated using the formula q = mcΔT, where q is the heat added, m is the mass, c is the specific heat, and ΔT is the change in temperature. From the graph, we see that the temperature of the solid phase increases by 20ºC when 40 cal of heat is added. Therefore, the specific heat of the solid phase is:
c = q/mΔT = 40 cal / 1.0 g x 20ºC = 0.25 cal/g · Cº.

Question 15

How much internal energy is contained in 1 mole of monatomic gas at STP?

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Question 16

The first law of thermodynamics is most closely related to

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The first law of thermodynamics is also known as the law of conservation of energy, which states that energy cannot be created or destroyed, only transferred or converted from one form to another. Therefore, it is most closely related to the conservation of energy.

Question 17

A state variable is one that allows other variables to be determined using a relationship. Which of the following variables are state variables?

Accepted Answer

P, V, and T are state variables as they allow determination of other variables such as internal energy and enthalpy using equations of state. Internal energy, U, is also a state variable as it can be determined based on the state variables. W and Q are not state variables as they depend on the process and not just the initial and final states.

Question 18

A small water reactor recently installed at Podunk College is operating at the boiling point of water due to the malfunctioning of the cooling system. The operators observe that the water boils away at the rate of 10 L/min. If they assume that all of the reactor energy is absorbed in the water, the power developed by the reactor is approximately

Accepted Answer

We can use the formula for power developed by a nuclear reactor:

P = ηρVq

where η is the efficiency of energy transfer, ρ is the density of water, V is the volume of water in the reactor, and q is the heat produced per unit time.

Assuming η = 1 and ρ = 1000 kg/m^3, and using the fact that 1 L = 0.001 m^3, we can find V:

10 L/min = 0.01 m^3/min
V = 0.01 m^3/min x 60 min/hr = 0.6 m^3/hr

Now, the heat produced per unit time is equal to the rate of boiling away of water times the latent heat of vaporization of water, which is 2.26 x 10^6 J/kg:

q = 10 L/min x 0.001 m^3/L x 1000 kg/m^3 x 2.26 x 10^6 J/kg = 22,600 W

Substituting these values into the formula for power, we get:

P = ηρVq = 1 x 1000 kg/m^3 x 0.6 m^3/hr x 22,600 W = 378 kW

Therefore, the best choice is D, 378 kW.

Question 19

Besides Joule's classic experiment, another way of demonstrating the equivalence between mechanical energy and heat is the following: Put some lead shot into a glass tube, seal both ends of the tube, invert the tube quickly several times, and measure the temperature of the shot. If you assume that all the mechanical energy is converted into heat in the lead shot and that no heat is lost, what is the change in the temperature of the shot if the tube is 1.0 m long, there are 100 g of shot, and the tube is inverted 10 times? (The specific heat of lead is 0.128 kJ/kg · K.)

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Question 20

In a certain thermodynamic process, 1000 cal of heat are added to a gas confined in a cylinder. At the same time, 1000 J of work are done by the gas as it expands. The increase in internal energy of the gas is

Accepted Answer

First, we need to convert the heat added to joules:
1000 cal = 1000 x 4.184 J = 4184 J
According to the first law of thermodynamics:
change in internal energy = heat added - work done
change in internal energy = 4184 J - 1000 J = 3184 J
Therefore, the increase in internal energy of the gas is 3184 J.

Quiz 18: Heat and the First Law of Thermodynamics