You’re making assumptions beyond the problem statement. The problem never says pressure is constant, so a temperature change does not imply a change in volume. (An inferred change in particle number could also change the density, but I’m guessing that wasn’t your mistake.)
You’re making assumptions beyond the problem statement. The problem never says pressure is constant, so a temperature change does not imply a change in volume. (An inferred change in particle number could also change the density, but I’m guessing that wasn’t your mistake.)