Chapter 17: Problem 36
For a process, \(w=34 \mathrm{~J}\) and \(q=-109 \mathrm{~J} .\) What is \(\Delta E\) for this process?
Short Answer
Expert verified
\( \Delta E = -75 \text{ J} \)
Step by step solution
01
Identify the Formula
To find the change in energy, \( \Delta E \), you need to use the first law of thermodynamics. The formula is \( \Delta E = q + w \), where \( q \) is the heat exchange and \( w \) is the work done by or on the system.
02
Substitute Known Values
Plug the given values into the formula. Here, \( q = -109 \text{ J} \) and \( w = 34 \text{ J} \). Substitute these into the formula: \( \Delta E = -109 + 34 \).
03
Perform the Calculation
Calculate \( \Delta E \) by performing the arithmetic operation. \( -109 + 34 = -75 \).
04
Interpret the Result
The outcome of the calculation is \( \Delta E = -75 \text{ J} \). This negative value indicates that the system has lost 75 joules of energy during the process.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Energy Change
The concept of energy change, or \( \Delta E \), is a fundamental part of understanding the first law of thermodynamics. According to this law, energy cannot be created or destroyed in an isolated system; it can only change forms.
In practical terms, this means the total energy of a system is the sum of the heat added to the system and the work done on the system.
In practical terms, this means the total energy of a system is the sum of the heat added to the system and the work done on the system.
- If \( \Delta E \) is positive, the system gains energy.
- If \( \Delta E \) is negative, the system loses energy.
Heat Exchange
Heat exchange, denoted by the symbol \( q \), refers to the transfer of thermal energy between a system and its surroundings. It is a crucial component in the analysis of thermodynamic processes.
When a system absorbs heat, \( q \) is positive, indicating energy is entering the system. Conversely, when a system releases heat, \( q \) is negative, denoting energy leaves the system. In the given problem, \( q = -109 \text{ J} \) indicates the system has lost 109 joules to its surroundings.
When a system absorbs heat, \( q \) is positive, indicating energy is entering the system. Conversely, when a system releases heat, \( q \) is negative, denoting energy leaves the system. In the given problem, \( q = -109 \text{ J} \) indicates the system has lost 109 joules to its surroundings.
- This loss of heat suggests an exothermic process.
- Heat exchange affects the system's energy balance, influencing the calculated \( \Delta E \).
Work Done
Work done, represented by \( w \), is another key element in the study of thermodynamics. It refers to the energy transferred by the system, excluding heat. Work can be done on the system or by the system.
A positive \( w \) means work is done on the system, adding energy to it. A negative \( w \) indicates work is done by the system, resulting in an energy loss. In our scenario, \( w = 34 \text{ J} \) means 34 joules of energy have been added to the system through work done on it.
A positive \( w \) means work is done on the system, adding energy to it. A negative \( w \) indicates work is done by the system, resulting in an energy loss. In our scenario, \( w = 34 \text{ J} \) means 34 joules of energy have been added to the system through work done on it.
- Work can involve processes such as compression or expansion of gases.
- It is essential to differentiate between heat exchange and work because they represent distinct ways energy can enter or leave a system.