Starter question

1. Starter question • Use collision theory to explain the following reactions: • Cut potatoes cooking faster than whole potatoes in water at 100oC • Stain remover added to the stain works faster than adding the stain remover in to the washing load with the detergent. • Mould grows faster on bread left on the counter than on bread kept in the fridge • How does adding a catalyst to a reaction affect the activation energy?

2. Equilibrium When we think of a chemical reaction we normally just think of reactants becoming products N2 + 3H2→ 2NH3 However this is only have the picture. Most reactions exist in a state of equilibrium This means that there is also a reverse reaction occuring. It is represented using an equilibrium arrow

3. A system that has reached equilibrium is said to be in dynamic equilibrium. This is because the rate of the forward reaction is equal to the rate of the reverse reaction Because This is a dynamic state if we subject the reaction to change then the equilibrium will change

4. Le Chatelier’s Principle • Named after Henry Louis de Chatelier • Worked at the Sorbonne in Paris • Tried unsuccessfully to make ammonia, NH3 by direct combination • Most famous for his work on equilibria

5. Le Chatelier’s Principle states; ‘If a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress’

6. Today’s Tasks • Find and write the definitions for the following words in your notes • Equilibrium, Equilibrium constant, Le Chatelier’s Principle, Endothermic, Exothermic • Complete the guided notes and answer the questions on the worksheet (you will need to do this to be able to answer the questions in the quiz later) Homework: The questions on the reverse of the sheet. Due tomorrow

7. Equilibrium This occurs when there ia a forward and a backward reaction occuring simultaneously. i.e. reactants are becoming products and products reactants. It is represented using Equilibrium constatnt Keq, which describes the ratio of product concentrations to reactant concentrations, with each raised to the power corresponding to its coefficient in the balanced equation

8. Le Chatelier’s Principle This states that when something is done to a system at equilibrium. The equilibrium position will move to minimize the effect of the change A reaction that takes in heat energy, feels cool ,∆H +ve Endothermic A reaction that releases heat energy, feels hot ,∆H -ve Exothermic