if you change to conditions of a reversible reaction at equilibrium the system will try and counteract that change
if the temperature decreases in a reversible reaction the equilibrium will move in the exothermic direction to produce more heat
if there is an increase in pressure for a reversible reaction the equilibrium tries to reduce it as it moves in the direction where there are fewer molecules of gas
if there is an increase in concentration of the reactants the system tries to decrease it by making more products
