Memory Anchor:

• Super Challenge:

  Stretch:

  Challenge:

Key Questions:

1. Why do some collisions between reactant particles not result in a product forming?
   • Chemical reactions can occur only when reacting Particles collide with each other and with sufficient Energy. This doesn't always happen.
2. What does the term activation energy mean?
   • The minimum amount of Energy that Particles must have to react is called the activation Energy.
3. What information can be shown in a reaction profile?
   • Reaction profiles can be used to show the relative energies of reactants and products, the activation Energy and the overall Energy change of a reaction.
4. What would the simple reaction profile for an exothermic reaction look like?
   • For an exothermic reaction the reaction profile would show the Energy level for the reactants to be lower than the Energy level for the products. A curved line is used to show the activation Energy required for the reaction (this is higher than the products Energy level)
5. What would the simple reaction profile for an endothermic reaction look like?
   • For an endothermic reaction the reaction profile would show the Energy level for the reactants to be higher than the Energy level for the products. A curved line is used to show the activation Energy required for the reaction (this is higher than the reactants Energy level)
6. What information does the activation energy provide?
   • The activation Energy is the Energy needed for a reaction to occur.
7. What energy transfers occur during breaking bonds of reactants and forming new bonds of products?
   • During a chemical reaction Energy must be supplied to break bonds in the reactants and Energy is released when bonds in the products are formed.
8. What information can bond energies provide?
   • Bond energies tell us the Energy needed to break bonds and the Energy released when bonds are formed.
9. How is the overall energy change of a reaction calculated?
   • The overall Energy change is calculated by working out the difference between the sum of the Energy needed to break bonds in the reactants and the sum of the Energy released when bonds in the products are formed is the overall Energy change of the reaction.
10. What happens in an exothermic reaction in terms of energy, bond making and bond breaking?
    • In an exothermic reaction, the Energy released from forming new bonds is greater than the Energy needed to break existing bonds.
11. What happens in an endothermic reaction in terms of energy, bond making and bond breaking?
    • In an endothermic reaction, the Energy needed to break existing bonds is greater than the Energy released from forming new bonds.
12. What is the energy transferred in the following chemical reaction: hydrogen bromide decomposing to form hydrogen and bromine? 2 ? (H?Br) ? H?H Br?Br The bond energies relevant to this reaction are shown below: H?Br 366 kJ/mol H?H 436 kJ/mol Br?Br 193kJ/mol
    • 1.Energy in = 2 ? 366 = 732 kJ/mole 2.Energy out = 436 + 193 = 629 kJ/mole 3.Energy change = in ? out = 732 ? 629 = +103 kJ/mole The Energy change is positive, showing that Energy is taken in from the surroundings in an endothermic reaction.