A 100g sample of water at 25 °C and 1 atm. of pressure. Then, 100g of water that has recently heated to 100 °C from 0 °C and then cooled to 25 °C at 1 atm. of pressure.

Correct answer: C. Has the same internal energy

  • A. Has more internal energy
  • B. Has less internal energy
  • C. Has the same internal energy
  • D. None of these

Explanation

The internal energy of a substance is dependent on its temperature, pressure, and phase, not on the path taken to reach that state. Both 100 g samples of water are at 25 °C and 1 atm pressure, meaning they have the same internal energy. The history of how they reached that temperature (whether they were heated then cooled or started at that temperature) does not affect the internal energy in the final state. Therefore, option C is correct. Options A and B are incorrect because they suggest a difference in internal energy that does not exist based on temperature alone. Option D is incorrect because option C is a valid and correct choice.

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