In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The capillary and diaphragm techniques measure a constant quantifying this process, and for low Reynolds number, that constant equals Boltzmann's constant times temperature over six pi times viscosity times particle radius. This phenomenon is used to introduce interstitial defects into crystals, such as carbon substitution for steel. This process controls the (*) rate of catalytic reactions with very high turnover numbers. A gradient of chemical potential is the thermodynamic driving force for this process. This process occurs through random walk in Brownian motion, and when it occurs through a semipermeable membrane, it's called osmosis. For 10 points, name this movement of molecules from high concentration to low concentration.
Science