text: This process changes the position of a metal-metal interface in the Kirkendall effect.
full_question: This process changes the position of a metal-metal interface in the Kirkendall effect. Spinodal decomposition occurs solely due to this process. Solutions to problems involving this process often contain the error function. This process is driven by a negative chemical potential gradient. The flux of this process is proportional to the negative gradient of the concentration according to Fick's first law. The rate at which this process occurs is proportional to one over the square root of molar mass according to Graham's law. For 10 points, name this process by which molecules travel from areas of high to low concentration.
first_sentence: This process changes the position of a metal-metal interface in the Kirkendall effect.
raw_answer: diffusion [prompt on "effusion"]