AP EAMCET Engineering 18 Sep 2020 Shift 1 Paper

In free expansion, the ideal gas is allowed to expand into a vacuum. This happens quickly, so there is no heat transferred. No work is done, because the gas does not displace anything. According to first law of thermodynamics, this means that
∆E‌intemal ‌=0
Hence, there is no change in internal energy of an ideal gas when it undergoes free expansion.