The correct statement that best explains why a mixture of different gases rises to the top of its container when heated is: Heated gases have higher kinetic energy and decreased density.
When gases are heated, their kinetic energy increases, causing the gas molecules to move faster. This increased motion generally leads to a decrease in density since the same mass of gas occupies a larger volume as the temperature rises (assuming constant pressure). Therefore, the heated gas becomes less dense than the cooler gases around it, causing it to rise.