Background Paragraph: Chemical equilibrium was studied by French chemist Henri Le Châtelier (1850-1936), and his description of how a system at equilibrium responds to a change in conditions has become known as Le Châtelier’s principle . This principle states that when a chemical system is at equilibrium and is disturbed by a stress, the system will respond by attempting to counteract that stress until a new equilibrium is established. Stresses to a chemical system include changes in the concentrations of reactants or products, changes in the temperature of the system, or changes in the pressure of the system. We will discuss each of these stresses separately. In each case, the change to the equilibrium position will cause either the forward or reverse reaction to be favored over the opposite process. When the forward reaction is favored, the concentrations of the products increase, and the concentrations of the reactants decrease. When the reverse reaction is favored, the concentrations of the products decrease, and the concentrations of the reactants increase. 
Story: David was conducting experiments on chemical equilibrium in the chemistry lab. First, he took a chemical system that was at equilibrium. He labeled it as case E. Then he changed the temperature of the system. He labeled that experiment as case T. Finally, he observed two more experiments, case A and case B. In case A forward reaction was favored, and in case B reverse reaction was favored.
In which case the products concentration would decrease, case A or case B? In which case the products concentration would increase, case A or case B? In which case the reactants concentration would decrease, case A or case B? In which case the reactants concentration would increase, case A or case B? In which case the system would not try to counteract, case E or case T? In which case the system would try to counteract, case E or case T? Would the products concentration increase or decrease in case A than in case B? Would the products concentration increase or decrease in case B than in case A? Would the reactants concentration increase or decrease in case A than in case B? Would the reactants concentration increase or decrease in case B than in case A?