A sample of an ideal gas at Pi is initially confined to one chamber of the apparatus represented above, and the other chamber is initially evacuated. The valve connecting the chambers is opened, and the gas expands at constant temperature to fill both chambers. What best describes ΔS for the process?

If the gas is ideal, the internal energy depends only on the temperature. Therefore, when an ideal gas expands freely, its temperature does not change.

When the valve of the chamber opens, the ideal gas expands and since, it is free to move its entropy increases. Entropy is a measure of uncertainty or randomness. Thus, ΔS becomes positive.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.