Questions and Answers
What does a positive sign of work indicate about the direction of energy transfer in a thermodynamic system?
A positive sign of work indicates that energy is being transferred from the system to the surroundings.
Using the first law of thermodynamics, how is the change in internal energy (ΔU) expressed in terms of heat (q) and work (w)?
The change in internal energy is expressed as ΔU = q - w.
What does a negative value of ΔE signify in a thermodynamic context?
A negative value of ΔE signifies that the system has released energy to the surroundings.
In the context of thermodynamics, how are internal energy and heat related during an isothermal process?
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In Sample Problem #2, how do you calculate the change in energy if a system performs work on the surroundings while absorbing heat?
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What is the First Law of Thermodynamics and how does it relate to internal energy?
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Explain the significance of work (w) in the context of energy transfer in thermodynamics.
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Describe how heat (q) differs from work (w) in thermodynamic processes.
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How does the sign convention for energy transfer impact the analysis of thermodynamic systems?
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In a closed system, if 100 J of heat is added and 30 J of work is done by the system, what is the change in internal energy?
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What does the First Law of Thermodynamics state regarding internal energy, work, and heat?
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In the context of the First Law, how is internal energy affected when a system loses heat?
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If a system does 94 J of work on its surroundings while losing 354 J of heat, what is the change in internal energy?
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What is the significance of work being done by a system in thermodynamic terms?
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How do you calculate the work done if a system has a net change of 0.500 kJ of internal energy and gains 143 J of heat?
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What does a negative work value signify in terms of energy flow?
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Explain what happens to internal energy when a system both gains heat and does work.
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Why is it important to consider both work and heat transfers when analyzing a thermodynamic system?
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Study Notes
First Law of Thermodynamics
- Energy cannot be created or destroyed, only transferred or converted between forms.
- Describes the relationship between internal energy, work, and heat in a system.
Internal Energy (E)
- Represents the total kinetic and potential energy of a system.
- Internal energy change is determined by the net gain or loss of energy:
- Positive change (+) indicates net gain.
- Negative change (–) indicates net loss.
Work (w)
- Defined as energy transferred when an object moves due to a force over a distance.
Heat (q)
- Energy transferred between a system and its surroundings due to a temperature difference.
Relationship Equation
- The internal energy change (ΔE) can be expressed as:
- ΔE = q + w
- This equation summarizes how heat and work contribute to the internal energy of a system.
Sample Problems
- Problem 1: A system loses 354 J of heat and performs 94 J of work. The change in internal energy can be calculated using the relationship ΔE = q + w.
- Problem 2: If a system has a net internal energy change of 0.500 kJ and gains 143 J of heat, the work done can be calculated, with the sign indicating the direction of work.
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Problem 3: For various cases, calculate the change in internal energy (ΔE):
- Case a: Absorbing 105 kJ of heat and doing 29 kJ of work results in a ΔE of 76 kJ.
- Case b: Releasing 57.5 kJ of heat and doing 22.5 kJ of work leads to a ΔE of -80 kJ.
Lesson Objectives
- Understand and explain the first law of thermodynamics.
- Define internal energy, work, and heat.
- Articulate the relationship among internal energy, work, and heat.
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Description
Test your understanding of the First Law of Thermodynamics, including concepts of internal energy, kinetic and potential energy, work, and heat. This quiz is designed for 10th-grade students at the Philippine Science High School, focusing on foundational chemistry principles.