Change in internal energy during vapourization of water

AI Thread Summary
The discussion centers on calculating the change in internal energy and heat absorbed during the vaporization of water at 100 degrees Celsius, assuming water behaves as an ideal gas. It is clarified that, despite the temperature remaining constant during vaporization, energy is required for the phase change, indicating that internal energy does not remain constant. The concept of latent heat is introduced, emphasizing that energy must be added for vaporization, known as the latent heat of vaporization. This energy requirement is crucial for understanding phase changes in water, including transitions to solid and vapor states. The confusion arises from the misconception that constant temperature implies constant internal energy, which is corrected through the discussion.
shivambehl
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Homework Statement


Assuming water to be an ideal gas, enthalpy of vaporization is x joules per mole. I have to find change in internal energy an 100 degree Celsius for one mole of water. also find heat absorbed.

Homework Equations

The Attempt at a Solution


I initially thought that during vaporization of water, temperature does not change and hence internal energy should remain constant (assuming ideal gas behaviour by water ).
but my assumption was found to be wrong.

I am totally confused...
 
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shivambehl said:

Homework Statement


Assuming water to be an ideal gas, enthalpy of vaporization is x joules per mole. I have to find change in internal energy an 100 degree Celsius for one mole of water. also find heat absorbed.

Homework Equations

The Attempt at a Solution


I initially thought that during vaporization of water, temperature does not change and hence internal energy should remain constant (assuming ideal gas behaviour by water ).
but my assumption was found to be wrong.

I am totally confused...
It takes energy to accomplish the phase change from liquid to vapor. The fact that this phase change occurs at constant temperature does not necessarily mean that the energy in the water is constant. Same deal when water changes phase from liquid to solid. Energy must be removed from the liquid water to turn it into ice. The energy which must be added/removed is known as latent heat. For freezing water, this is the latent heat of fusion. For making steam, this is the latent heat of vaporization.

https://en.wikipedia.org/wiki/Latent_heat
 

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