GCSE Chemistry AQA- Energy Changes

Activation Energy - The minimum amount of energy required to start a chemical reaction. Advantages of using hydrogen as a fuel? - - doesn't use up oil resources - no pollutants - doesn't contribute to greenhouse effect - water is waste product - fuel cells don't need to recharge - fuel cell can be any size - solar panels can be used to produce electricity to extract hydrogen instead of electricity which gives off fossil fuels bond breaking is - endothermic: requires energy Bond energies - The energy needed to break the bond between two atoms is called the bond energy for that bond. You can use bond energies to calculate overall energy change in a chemical reaction using bond energies. (ENERGY IN - ENERGY OUT). bond energy - energy needed to break the bond between 2 atoms bond making is - exothermic: gives off energy Can primary cells be recharged? Why? - Cannot be recharged. Once one of the reactants has run out the cell stops working and should be disposed of in a recycling centre Cells and Batteries - A simple cell can be made by connecting 2 different metals in contact with an electrolyte. A battery consists of 2 more cells giving greater voltage. CH4(g)+2H2O(g) ⇌ CO2(g)+4H2(g) ∆H= +165 1. Is this endothermic or exothermic 2. What do you do to temperature to get maximum yield of products 3. What would you do to pressure to get maximum yield of products - 1. Endothermic 2. High 3. Low CH4(g)+H2O(g) ⇌ CO(g) + 3H2(g