Thermodynamics - Physics
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In order for heat transfer to occur, which of the following must be present?
In order for heat transfer to occur, which of the following must be present?
A temperature gradient is always needed for heat transfer to occur. The temperature difference is what drives a flow of heat, as heat will always travel from an area of higher temperature to an area of lower temperature. This can occur between two materials, or within a single material. For example, if an iron pot is placed on a stovetop, the entire metal pot will become hot even though only the bottom is in contact with the heat source. This is because the heat transfers through the metal, from the high heat at the bottom to the lower heat at the top.
A temperature gradient is always needed for heat transfer to occur. The temperature difference is what drives a flow of heat, as heat will always travel from an area of higher temperature to an area of lower temperature. This can occur between two materials, or within a single material. For example, if an iron pot is placed on a stovetop, the entire metal pot will become hot even though only the bottom is in contact with the heat source. This is because the heat transfers through the metal, from the high heat at the bottom to the lower heat at the top.
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A piece of bread is burned on one side and uncooked on the other after being heated in a toaster. What was the most likely form of heat transfer to cause the burn?
A piece of bread is burned on one side and uncooked on the other after being heated in a toaster. What was the most likely form of heat transfer to cause the burn?
Conduction is a form of heat transfer requiring direct contact between two objects. In the question, the burned side of the bread was likely in direct contact with the heat source, while the other was only in contact with hot air. The burned side is heated by conduction, while the uncooked side is heated by convection.
Convection is the transfer of heat through a fluid medium, namely a liquid or gas. Radiation is the transfer of heat through electromagnetic waves.
Conduction is a form of heat transfer requiring direct contact between two objects. In the question, the burned side of the bread was likely in direct contact with the heat source, while the other was only in contact with hot air. The burned side is heated by conduction, while the uncooked side is heated by convection.
Convection is the transfer of heat through a fluid medium, namely a liquid or gas. Radiation is the transfer of heat through electromagnetic waves.
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Which of the following methods of heat transfer requires the two objects to be touching?
Which of the following methods of heat transfer requires the two objects to be touching?
Conduction is the form of heat transfer that requires direct contact between two objects.
Radiation is heat transfer via electromagnetic radiation. Convection uses a fluid medium, such as air or water, for heat transfer. Induction and thermodynamic discharge are not recognized types of heat transfer.
Conduction is the form of heat transfer that requires direct contact between two objects.
Radiation is heat transfer via electromagnetic radiation. Convection uses a fluid medium, such as air or water, for heat transfer. Induction and thermodynamic discharge are not recognized types of heat transfer.
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A marshmallow on a stick is placed above a fire, but not touching the fire. The marshmallow heats up and softens. How is the marshmallow being heated?
I. Conduction
II. Convection
III. Radiation
A marshmallow on a stick is placed above a fire, but not touching the fire. The marshmallow heats up and softens. How is the marshmallow being heated?
I. Conduction
II. Convection
III. Radiation
Conduction occurs when heat is transferred by direct contact between two objects. Convection occurs when heat is transferred via contact between a fluid and an object. Radiation is heat transfer via electromagnetic radiation.
In this question, the fire is a source of heat and electromagnetic radiation. When the radiation from the fire impacts the marshmallow, it is being heated by radiation. The fire is also heating the surrounding air, creating fluid currents. The heated air is also transferring energy to the marshmallow, heating by convection.
There is no conduction in this example.
Conduction occurs when heat is transferred by direct contact between two objects. Convection occurs when heat is transferred via contact between a fluid and an object. Radiation is heat transfer via electromagnetic radiation.
In this question, the fire is a source of heat and electromagnetic radiation. When the radiation from the fire impacts the marshmallow, it is being heated by radiation. The fire is also heating the surrounding air, creating fluid currents. The heated air is also transferring energy to the marshmallow, heating by convection.
There is no conduction in this example.
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Enthalpy is a measure of __________.
Enthalpy is a measure of __________.
Enthalpy, or 
, is the total energy of a thermodynamic system. Similar to how mechanical energy can change during mechanical processes, involving changing distances of velocities, enthalpy will increase or decrease with changes made to the thermodynamic state of the system. It is simply a measure for a different form of energy.
Enthalpy, or
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An ice cube melts into water. While it is melting, what is the temperature of the mixture doing?
An ice cube melts into water. While it is melting, what is the temperature of the mixture doing?
When an object is changing forms (solid to liquid in this case), the temperature remains constant. All of the energy that would normally go towards changing the internal temperature of the object is going into the latent heat of fusion or enthalpy of fusion instead.
When an object is changing forms (solid to liquid in this case), the temperature remains constant. All of the energy that would normally go towards changing the internal temperature of the object is going into the latent heat of fusion or enthalpy of fusion instead.
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Entropy is a measure of __________.
Entropy is a measure of __________.
Entropy is the measurement of disorder within a system, or how far it is from thermal equilibrium. Remember that everything in nature tends towards an equilibrium. The further from that equilibrium something is, the more "disordered" it is when compared to nature's preferred state.
Entropy is the measurement of disorder within a system, or how far it is from thermal equilibrium. Remember that everything in nature tends towards an equilibrium. The further from that equilibrium something is, the more "disordered" it is when compared to nature's preferred state.
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A glass of cold water is placed in a sealed room. After an infinite amount of time, what will happen?
A glass of cold water is placed in a sealed room. After an infinite amount of time, what will happen?
The second law of thermodynamics states that closed systems constantly move towards a state of thermal equilibrium. Since we are looking at a closed system, that means we must be moving towards a state of equilibrium. The only way that happens is if the air cools and the water warms, until they both reach a new final temperature.
Looking at this question in terms of heat transfer, we can infer that the glass of water will warm up, but there must be a transfer of heat to the glass in order for this to occur. The heat comes from the air, causing it to cool as the glass warms.
The second law of thermodynamics states that closed systems constantly move towards a state of thermal equilibrium. Since we are looking at a closed system, that means we must be moving towards a state of equilibrium. The only way that happens is if the air cools and the water warms, until they both reach a new final temperature.
Looking at this question in terms of heat transfer, we can infer that the glass of water will warm up, but there must be a transfer of heat to the glass in order for this to occur. The heat comes from the air, causing it to cool as the glass warms.
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An object can never reach absolute zero in a finite number of steps. Which of these laws supports this statement?
An object can never reach absolute zero in a finite number of steps. Which of these laws supports this statement?
The third law of thermodynamics states that it is impossible to decrease the temperature of a system to absolute zero in a finite number of steps. To do so would require that the entropy of the system also reaches zero, suggesting that the atoms cease vibrating in the material and it has zero net energy. Such a process is not possible.
The third law of thermodynamics states that it is impossible to decrease the temperature of a system to absolute zero in a finite number of steps. To do so would require that the entropy of the system also reaches zero, suggesting that the atoms cease vibrating in the material and it has zero net energy. Such a process is not possible.
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Gas A is in thermal equilibrium with gases B and C. Which of the following is a valid conclusion?
Gas A is in thermal equilibrium with gases B and C. Which of the following is a valid conclusion?
The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they are in equilibrium with each other. If gas A is in equilibrium with gas B and gas C, then gas be and gas C must be in thermal equilibrium with each other.
The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they are in equilibrium with each other. If gas A is in equilibrium with gas B and gas C, then gas be and gas C must be in thermal equilibrium with each other.
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A certain amount of heat energy is added to a closed system. A few moments later, a scientist observes that the total increase in energy is LESS than that heat energy added to the system. Which could be a valid explanation for this conclusion?
A certain amount of heat energy is added to a closed system. A few moments later, a scientist observes that the total increase in energy is LESS than that heat energy added to the system. Which could be a valid explanation for this conclusion?
The most likely explanation is that work is done by the system.
The formula for change in energy shows that the net change in energy is equal to the increase in heat energy minus the work done:
Since 
, there must have been work done by the system.
The most likely explanation is that work is done by the system.
The formula for change in energy shows that the net change in energy is equal to the increase in heat energy minus the work done:
Since
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A gas in a closed container is heated with 
of energy, causing the lid of the container to rise 
with 
of force. What is the total change in energy of the system?
A gas in a closed container is heated with
For this problem, use the first law of thermodynamics. The change in energy equals the increase in heat energy minus the work done.
We are not given a value for work, but we can solve for it using the force and distance. Work is the product of force and displacement.
Now that we have the value of work done and the value for heat added, we can solve for the total change in energy.
For this problem, use the first law of thermodynamics. The change in energy equals the increase in heat energy minus the work done.
We are not given a value for work, but we can solve for it using the force and distance. Work is the product of force and displacement.
Now that we have the value of work done and the value for heat added, we can solve for the total change in energy.
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A gas in a closed container is heated, causing the lid of the container to rise. The gas performs 
of work to raise the lid, such that is has a final total energy of 
. How much heat energy was added to the system?
A gas in a closed container is heated, causing the lid of the container to rise. The gas performs
For this problem, use the first law of thermodynamics. The change in energy equals the increase in heat energy minus the work done.
We are given the amount of work done by the gas and the total energy of the system. Using these values, we can solve for the heat added.
For this problem, use the first law of thermodynamics. The change in energy equals the increase in heat energy minus the work done.
We are given the amount of work done by the gas and the total energy of the system. Using these values, we can solve for the heat added.
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A gas in a closed container is heated with 
of energy, causing the lid of the container to rise. If the change in energy of the system is 
, how much work was done by the system?
A gas in a closed container is heated with
For this problem, use the first law of thermodynamics. The change in energy equals the increase in heat energy minus the work done.
We are given the total change in energy and the original amount of heat added. Using these values, we can solve for the work done by the system.
For this problem, use the first law of thermodynamics. The change in energy equals the increase in heat energy minus the work done.
We are given the total change in energy and the original amount of heat added. Using these values, we can solve for the work done by the system.
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Which of the following represents the first law of thermodynamics?
Which of the following represents the first law of thermodynamics?
The first law of thermodynamics is another wording of the law of conservation of energy. Effectively it states that energy cannot be created or destroyed, but it can change forms.
This means that, in the given situation of the ball rolling down the hill, the total initial energy equals the final kinetic energy plus heat.
The zeroth law of thermodynamics states that if a system is in equilibrium with two other systems, then the two other systems are in equilibrium with each other.
The second law of thermodynamics states that the entropy of a closed system will always increase.
The third law of thermodynamics states that absolute zero is the temperature at which entropy is zero.
The first law of thermodynamics is another wording of the law of conservation of energy. Effectively it states that energy cannot be created or destroyed, but it can change forms.
This means that, in the given situation of the ball rolling down the hill, the total initial energy equals the final kinetic energy plus heat.
The zeroth law of thermodynamics states that if a system is in equilibrium with two other systems, then the two other systems are in equilibrium with each other.
The second law of thermodynamics states that the entropy of a closed system will always increase.
The third law of thermodynamics states that absolute zero is the temperature at which entropy is zero.
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According to the first law of thermodynamics, in an isothermal process __________.
According to the first law of thermodynamics, in an isothermal process __________.
According to the first law of thermodynamics, change in internal energy of a closed system is given by the difference between the heat energy added to the system and the work done by the system:
In an isothermal process, temperature is constant. Temperature is a measure of internal energy of the system. If temperature is constant, then there is no fluctuation of internal energy.
It can be implied that heat added to the system is equal to work done by the system.
According to the first law of thermodynamics, change in internal energy of a closed system is given by the difference between the heat energy added to the system and the work done by the system:
In an isothermal process, temperature is constant. Temperature is a measure of internal energy of the system. If temperature is constant, then there is no fluctuation of internal energy.
It can be implied that heat added to the system is equal to work done by the system.
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Three substances are added to a mug to make coffee: the coffee, which is 
, the milk, which is 
, and the sugar, which is in thermal equilibrium with the coffee. Describe the thermal state of the sugar.
Three substances are added to a mug to make coffee: the coffee, which is
The zeroth law of thermodynamics states that if two objects are in thermodynamic equilibrium with a third object, then they must be in thermodynamic equilibrium with each other. In this question, the coffee is in equilibrium with both the milk and the sugar, allowing us to conclude that the milk and sugar must be in equilibrium with each other.
The second law of thermodynamics states that the entropy of the universe is always increasing, and is not relevant to this particular scenario.
The zeroth law of thermodynamics states that if two objects are in thermodynamic equilibrium with a third object, then they must be in thermodynamic equilibrium with each other. In this question, the coffee is in equilibrium with both the milk and the sugar, allowing us to conclude that the milk and sugar must be in equilibrium with each other.
The second law of thermodynamics states that the entropy of the universe is always increasing, and is not relevant to this particular scenario.
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System A is in equilibrium with system C.
System B is in equilibrium with system C.
System A is in equilibrium with system B according to which law of thermodynamics?
System A is in equilibrium with system C.
System B is in equilibrium with system C.
System A is in equilibrium with system B according to which law of thermodynamics?
The zeroth law of thermodynamics states that if two separate systems are in equilibrium with a third system, then they are in equilibrium with each other. The zeroth law of thermodynamics is essentially equivalent to the transitive property of mathematics.
If 
and 
, then 
.
The first law of thermodynamics states that internal energy changes due to heat flow. Mathematically, this law is presented as 
.
The second law of thermodynamics states that the entropy (or disorder) of the universe is always increasing. Certain systems exist in which there is a local decrease in entropy, but these processes are always balanced by an increase of entropy outside of the system.
The third law of thermodynamics states that absolute zero is the state in which a system has zero entropy. Essentially, this means that it is impossible to reach absolute zero (at least with modern technology).
The zeroth law of thermodynamics states that if two separate systems are in equilibrium with a third system, then they are in equilibrium with each other. The zeroth law of thermodynamics is essentially equivalent to the transitive property of mathematics.
If
The first law of thermodynamics states that internal energy changes due to heat flow. Mathematically, this law is presented as
The second law of thermodynamics states that the entropy (or disorder) of the universe is always increasing. Certain systems exist in which there is a local decrease in entropy, but these processes are always balanced by an increase of entropy outside of the system.
The third law of thermodynamics states that absolute zero is the state in which a system has zero entropy. Essentially, this means that it is impossible to reach absolute zero (at least with modern technology).
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An ideal gas is inside of a tube at 
. If the pressure remains constant, but the volume decreases from 
to 
, what will be the final temperature in the tube?
An ideal gas is inside of a tube at
For this problem, use Charles's Law:
In this formula, 
is the volume and 
is the temperature. Charles's Law allows us to set up a proportion for changes in volume and temperature, as long as pressure remains constant. Since we are dealing with a proportion, the units for temperature are irrelevant and we do not need to convert to Kelvin.
Using the given values, we should be able to solve for the final temperature.
Cross multiply.
For this problem, use Charles's Law:
In this formula,
Using the given values, we should be able to solve for the final temperature.
Cross multiply.
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An ideal gas is inside of a container with a pressure of 
. If it starts with a volume of 
and is compressed to 
, what is the new pressure if the temperature remains constant?
An ideal gas is inside of a container with a pressure of
We will need to use Boyle's Law to solve:
Boyle's Law allows us to set up a relationship between the changes in pressure and volume under conditions with constant temperature. Since the equation is a proportion, we do not need to convert any units.
We can use the given values to solve for the new pressure.
We will need to use Boyle's Law to solve:
Boyle's Law allows us to set up a relationship between the changes in pressure and volume under conditions with constant temperature. Since the equation is a proportion, we do not need to convert any units.
We can use the given values to solve for the new pressure.
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