Equilibrium.
diffusion occurs due to differences in concentration of substances in different regions. then substances will naturally spread out (due to innate Brownian kinetic energy). the spreading I. e. diffusion will stop until equilibrium is achieved.
note: those substance particles are still moving due to the innate Brownian kinetic energies!
practice with people (parents, friends, siblings) and ask them to ask questions during it so you can learn how to keep focus and memorization, or practice in front of stuffed animals. read it out loud on recording, then practice saying it with the recording without the words in front of you. you'll do great! :)