Thermodynamics sealed piston Problem

In summary, the problem involves a sealed piston containing 1 kg of water at room temperature. The water is heated until it boils and then further heated until it reaches a final temperature of 150°C. The final volume of the water molecules inside the system is determined to be 1.95 m3. The work done by the system at constant pressure is 194900 Joules. The system gains energy by doing work, and the final state has a higher energy than the initial state.
  • #1
Bgerst103
32
0

Homework Statement



You have a sealed piston with a VERY LIGHT and moveable top that can easily slide up and down without friction.
It starts at room temperature with 1 kg of water in the bottom.
You heat it, boil the water, and further heat the water until it is at 150°C.
Determine the final volume of the water molecules inside the system. Remember to give the answer in m3.

Work done by a system at constant pressure is given by:
ΔW = pΔV
How much work (in Joules) did the piston do?

Did the system lose energy of gain energy by doing work??
A. The system gained energy by doing work
B. The system gained energy because we did work on it.
C. Doing work always causes a loss of energy to the system

True or False:
Although the system lost energy by doing work, it actually gained more energy because the final temperature was higher than the initial temperature. The energy it gained was from heat transfer of energy from the heat source to the water molecules. Thus, it gained more heat energy than it lost in work energy and the final state is higher energy than the initial state.

Homework Equations





The Attempt at a Solution



Part 1:
V= mass of water/density -> .001 m3
T1= 25+273.15= 298.15 K
T2= 150+273.15= 423.15 K
n= 1000/18= 55.5556 mols
R= 8.314
P=100,000 Pa
V=nRT2/P -> 1.95 m3
Part 2:
dW=pdV
100,000 (1.95-.001) ->194900
Part 3:
C?
Part 4:
Not really sure, false?

Overall, not totally sure of my calculations, just want someone to look them over and see if anything's incorrect.
 
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  • #2
I'm having trouble understanding the problem description. What is a "sealed piston?" Can you please describe the initial system more precisely (a diagram, if available)?

Chet
 
  • #3
All correct except part 4 which is true.
 
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  • #4
Chestermiller said:
I'm having trouble understanding the problem description. What is a "sealed piston?" Can you please describe the initial system more precisely (a diagram, if available)?

Chet

A sealed piston is one that doesn't leak.
 
  • #5
Chestermiller said:
I'm having trouble understanding the problem description. What is a "sealed piston?" Can you please describe the initial system more precisely (a diagram, if available)?

Chet

Chet, I see the initial system as 1 kg of water in a cylinder with the piston resting on the water's surface so there is no water vapor to start with. So it looks to me like the OP's computations are correct.

Seems like none of A, B or C is correct, but the follow-up statement is.
 
  • #6
rude man said:
Chet, I see the initial system as 1 kg of water in a cylinder with the piston resting on the water's surface so there is no water vapor to start with. So it looks to me like the OP's computations are correct.

Seems like none of A, B or C is correct, but the follow-up statement is.
Thanks Rude Man. It looks like all the OPs questions have now been answered.

Chet
 

FAQ: Thermodynamics sealed piston Problem

What is the "Thermodynamics sealed piston problem"?

The Thermodynamics sealed piston problem is a theoretical problem that involves a piston in a sealed container filled with gas. The piston is initially at equilibrium and then undergoes a series of processes, such as compression or expansion, which changes the state of the gas. The goal of the problem is to determine the final state of the gas and the work done by the gas during the process.

How is the "Thermodynamics sealed piston problem" solved?

The problem can be solved using the laws of thermodynamics, specifically the first and second laws. These laws govern the relationships between the internal energy, heat, and work of a system. By applying these laws and using the given information about the initial and final states of the gas, the final state and work done can be calculated.

What are the assumptions made in the "Thermodynamics sealed piston problem"?

There are several assumptions made in the problem, including: 1) The gas is an ideal gas, meaning it follows the ideal gas law; 2) The piston is frictionless and adiabatic, meaning there is no heat exchange between the gas and the surroundings; and 3) The process is reversible, meaning it can be reversed without any losses.

What is the significance of the "Thermodynamics sealed piston problem"?

The problem is significant because it demonstrates the application of the fundamental laws of thermodynamics in a real-world scenario. It also helps to illustrate concepts such as work, heat, and internal energy, and how they are related in a thermodynamic system. Additionally, the problem is relevant in many engineering applications, such as in the design of engines and refrigeration systems.

How does the "Thermodynamics sealed piston problem" relate to other thermodynamic problems?

The "Thermodynamics sealed piston problem" is similar to other thermodynamic problems, such as the Carnot cycle and the Otto cycle, in that it involves a closed system undergoing a series of processes. However, the specific conditions and assumptions in the "Thermodynamics sealed piston problem" make it a unique problem that requires its own approach and solution method.

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