Temperature and Internal Energy

Students observe changes in molecular speed when they control the absolute temperature of a gas sample. In a follow-on simulation, students observe changes in molecular speed when they control the molecular mass of the gas sample. This simple little simulation effectively explores the relationship between absolute temperature and kinetic energy (and therefore internal energy) of gas molecules. By controlling the temperature of a gas sample, the student can see that the higher the temperature, the faster the molecules are moving. Importantly, the observed changes are clearly not linear, which underscores that kinetic energy, and not speed, is directly related to absolute temperature, and kinetic energy is proportional to the square of the speed. A second simulation is provided in which the temperature is held constant, and the student controls the mass of the gas atoms. An inverse relationship between molecular speed and molecular mass is observed, which enables the student to see that for a constant temperature (constant kinetic or internal energy), increasing the mass will decrease the speed.