C7

• Exothermic reactions release energy and temperature increases.
• Exothermic reactions produces less energy content than reactants.
• Endothermic reactions absorb energy and temperature decreases.
• Endothermic reactions produces more energy than products.
• Activation energy is the minimum amount of energy the reactant particles require in order to collide with each other and react.
• overall energy change of a reaction =

  Energy required to break the bonds of the reactants - energy released by forming bonds.
• Negative energy change is a exothermic reaction
• Rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external electrical current is supplied.
• Hydrogen fuel cell helps reduce global warming as it doesn't produce carbon dioxide and only waste product is water.
• Hydrogen fuel cells is highly flammable and is difficult to store.
• Negative electrons attracted to anode and positive electrons attracted to cathode.
• As fuel enters the cell it sets up a potential difference across the cell allowing to drive the electrons around the circuit.