In this virtual lab activity, students use the online PHET simulation called "reactions & rates" to investigate how equilibrium changes based on stress to equilibrium. Stress includes adding or removing product or reactant and increasing and decreasing the temperature. Students SHOULD already be familiar with potential energy diagrams and endothermic and exothermic reactions. This corresponds to 3.4j and 3.4v major understanding and skill on the New York State chemistry core curriculum. Students discover and summarize that adding reactant and product shifts the equilibrium AWAY from the addition to counteract the addition. And students learn that increasing temperature favors the endothermic reaction.