Question

in an experiment, a scientist combines two gases of different temperatures in an insulated container. after a period, the scientist observes no change in total energy but a uniform temperature between the gases. what best describes this system?
the energy was redistributed throughout until thermal equilibrium occurred.
the energy from the warmer gas was reduced, and the cooler gas gained energy.
the energy of the system was entirely lost during the process.
the system did not behave according to the second law of thermodynamics.

Explanation:

• Option 1: When two gases of different temperatures are combined in an insulated container (no heat exchange with the outside), energy is redistributed between the gases. Thermal equilibrium is reached when there is a uniform temperature. This is in line with the first law of thermodynamics (energy conservation) as the total energy remains the same.
• Option 2: While it is true that the warmer gas loses energy and the cooler gas gains energy, this option does not mention the key concept of thermal equilibrium (uniform temperature) which is a more comprehensive description of the final state of the system.
• Option 3: The problem states that there is no change in total energy. So, the claim that energy is entirely lost is incorrect as it violates the first law of thermodynamics (energy conservation).
• Option 4: The second law of thermodynamics is about entropy (a measure of disorder). In this case, the process (heat transfer from hot to cold gas until thermal equilibrium) is in accordance with the second law (entropy of the universe - here the system of two gases - increases during the process of reaching thermal equilibrium).

Answer:

The energy was redistributed throughout until thermal equilibrium occurred.