General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of solution-pairs are explored: (i) a visualization of laminar flow at the interface between two dye-colored fluid streams; (ii) an acid-base reaction at the fluid-fluid interface; and (iii) a precipitation reaction of calcium carbonate (calcite) crystals at the fluid-fluid interface. These laboratory exercises provide a simple and effective means to expose students to the unique physical behaviors that result under confined flow. (Contains 5 figures.)