In Le Chatelier’s Principle, there are three changes you should know: change in concentration, change in volumn, anc change in temperature. First stop, I would give you a little hints about what they are.

• Change in concentration means when you add more concentration to the products or reactants of a given reaction. If you increase the concentration on either the products or the reactants, the equilibrium will shift to the opposite side. If you decrease the concentration on either the products or the reactants, the equilibrium will shift to the same side ( I will talk more about what equilibrium is later).

For example: 2H2(g) + O2(g) -> <- 2H2O(g)      If we increase (O2) the quilibrium will shift to the right side.

• Change in volumn means when you compress a reaction to make it smaller or when you decompress a reaction to make it become bigger. If you increase the volumn, the equilibrium will shift to the side with more gas molecules. If you decrease the volumn, the equilibrium will shift to theside with less gas molecules.

For example: N2(g) + 3H2(g) -> <- 2NH3(g)      If we increase the volumn the quilibrium will shift to the left.

• Change in temperature means when you add more or less heat the a given reaction. Endothermic means heat goes in (heat is a reactant). Exothermic means heat goes out (heat is a product).

For example: N2(g) + 3H2(g) -> <- 2NH3(g) + heat     If we increase the temperature the equilibrium will shift to the left. Because heat is on the side of the product, to make it balance, the equilibrium must shift to the left side to balance out the reaction.

     Equilibrium means the concentration of reactants or products in a reaction system at equilibrium always stay balance. Chemical equilibrium is a dynamic state where the concentrations of the reactants and the products remain constant over time, as long as the conditions are not changed.

Here are some facts you should know about equilibrium:

• The collision model is molecules must collide in order to react; used to account for the fact that reaction rate depends on concentrations of reactants and temperature.
• Not all collisions result in a chemical reaction because the answer lies in the fact that not all collisions posses enough energy to break bond.
• A catalyst speeds up a reaction without being consumed. A catalyst works because it provides a new pathway for the reaction.
• Homogeneous reaction is a reaction involving reactants and products in the same state. On the other hand, heterogeneous reaction is a reaction involving reactants and products in different states.
• Nature of reactants: Substances vary greatly in their tendency to react depending on their bond strengths and structures.
• Concentration (pressure): The rate of a homogenous reaction depends on the number of collisions that occur between reactants. Reaction rates typically increase as concentration (solution reactions) or pressure (gaseous reactions) increases.