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Questions and Answers
What sign convention is used when energy leaves the system?
What sign convention is used when energy leaves the system?
Which of the following statements about entropy change (ΔS) is true?
Which of the following statements about entropy change (ΔS) is true?
What is true when work is done on the system?
What is true when work is done on the system?
What defines the relationship between internal energy change (ΔU) and work (w)?
What defines the relationship between internal energy change (ΔU) and work (w)?
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In a closed system, which equation reflects the relationship when volume is constant?
In a closed system, which equation reflects the relationship when volume is constant?
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What is the sign of ΔH when a reaction is exothermic?
What is the sign of ΔH when a reaction is exothermic?
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According to the first law of thermodynamics, what is true about the change in internal energy of the universe?
According to the first law of thermodynamics, what is true about the change in internal energy of the universe?
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What happens in terms of energy when heat is added to a system?
What happens in terms of energy when heat is added to a system?
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Which type of system allows the transfer of both matter and energy?
Which type of system allows the transfer of both matter and energy?
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What distinguishes state functions from path functions in thermodynamics?
What distinguishes state functions from path functions in thermodynamics?
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In the context of thermodynamics, which of the following is considered an intensive property?
In the context of thermodynamics, which of the following is considered an intensive property?
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What happens to temperature when combining two equal masses of water at the same temperature?
What happens to temperature when combining two equal masses of water at the same temperature?
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Which of the following correctly describes extensive properties?
Which of the following correctly describes extensive properties?
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Which of the following statements about path functions is true?
Which of the following statements about path functions is true?
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A bomb calorimeter is defined as which type of thermodynamic system?
A bomb calorimeter is defined as which type of thermodynamic system?
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Which of the following is not a characteristic of intensive properties?
Which of the following is not a characteristic of intensive properties?
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Which statement about the conservation of internal energy is true?
Which statement about the conservation of internal energy is true?
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In the equation ΔU = q + w, what does 'q' represent?
In the equation ΔU = q + w, what does 'q' represent?
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When the internal energy change (ΔU) is calculated to be 4 kJ, what can be inferred?
When the internal energy change (ΔU) is calculated to be 4 kJ, what can be inferred?
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What is the correct calculation of ΔU when 500 kJ of work is done by a system and it releases 300 kJ of energy as heat?
What is the correct calculation of ΔU when 500 kJ of work is done by a system and it releases 300 kJ of energy as heat?
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Which of the following statements about endothermic reactions is accurate?
Which of the following statements about endothermic reactions is accurate?
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Given the equation for enthalpy change (ΔH = Hproducts - Hreactants), how would you classify a reaction with a ΔH of 50 kJ?
Given the equation for enthalpy change (ΔH = Hproducts - Hreactants), how would you classify a reaction with a ΔH of 50 kJ?
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What value of q implies that heat is given off by the system?
What value of q implies that heat is given off by the system?
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If a reaction releases 250 kJ of energy and does 500 kJ of work, what is the total change in internal energy?
If a reaction releases 250 kJ of energy and does 500 kJ of work, what is the total change in internal energy?
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Study Notes
Open, Closed, and Isolated Systems
- Open systems allow transfer of matter and energy
- Closed systems allow transfer of energy, but not matter
- Isolated systems do not allow transfer of matter or energy
- Bomb calorimeters are examples of isolated systems due to insulation
State Functions vs Path Functions
- State functions describe the initial and final states of a system
- State functions are calculated as "final - initial"
- Example: Temperature change in taking water from room temperature to sun, then to the North Pole and back to room temperature
- Path functions consider the pathway or mechanism in a given process
- Examples: Heat (q) and work (w)
- Example: Work (w) done pushing a box around a room depends on the path taken
Extensive vs Intensive Properties
- Extensive properties are additive
- Examples: Volume, mass, moles, and energy
- If you combine two buckets of water, the volume doubles
- Intensive properties are not additive, they define a system
- Examples: Temperature, density, and pressure
- If you combine two buckets of water at 25 degrees Celsius the temperature remains at 25 degrees
Thermodynamic Signs
- The sign of a thermodynamic variable is negative if it leaves the system
- The sign of a thermodynamic variable is positive if it enters the system
- For example: When heat (q) leaves the system, the sign is negative
- ΔG is negative for a spontaneous process and positive for a non-spontaneous process
- ΔS is positive for increasing disorder and negative for increasing order
- ΔH is negative for an exothermic process and positive for an endothermic process
Heat vs Work
- Heat is chaotic energy
- Work is a concerted flow of energy that can be controlled
- Both are path functions
Internal Energy and Enthalpy Theory
- The first law of thermodynamics states that ΔUuniv = 0, meaning energy is conserved
- ΔU = q + w
- U (internal energy) is a measure of all potential and kinetic energy in a system
- Calorimetry measures unknown ΔU reactions using ΔUsys = -ΔUsurrondings
- ΔH = ΔU + PΔV
- In a closed system, ΔU = qv, because volume is constant (no PΔV work)
- In an open system, ΔH = qp, because pressure is constant
Calculating Internal Energy
- Internal energy is calculated using the equation ΔU = q + w
- For work: + indicates work is entering the system, - indicates work leaving the system
- For heat: + indicates heat entering the system, - indicates heat leaving the system
Energy Diagrams of Reactions
- Energy entering the system indicates a positive ΔU
- Energy leaving the system indicates a negative ΔU
- ΔH = Hproducts - Hreactants
- An increase in energy on the energy diagram is endothermic
- A decrease in energy on the energy diagram is exothermic
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Description
Test your understanding of open, closed, and isolated systems, as well as state functions versus path functions. This quiz also covers extensive and intensive properties, providing a comprehensive overview of thermodynamic principles. Perfect for students in chemistry or physics.
