Which of the following has the lowest kinetic energy?

25 g of Na at 25 degrees C. Sodium is a solid at that temperature. All the other choices are gases. The "kinetic energy" refers to the amount of molecular motion -- how freely the molecules can move about each other. Solids have the least kinetic energy, followed by liquids and gases. So even though sodium is at 25 degrees (the highest temperature), as it is a solid, it has the lowest kinetic energy.