Reactivity 1.1.3
Energy Profiles
Visualizing the energy pathway from reactants to products.
Exothermic Profile
- Result: Products have LESS energy than Reactants.
- Energy Released: Lost as heat to surroundings.
Endothermic Profile
- Result: Products have MORE energy than Reactants.
- Energy Absorbed: Taken from surroundings.
Deep Think Concept
Key Definitions
Activation Energy ()
The minimum energy required for colliding particles to react (to reach the Transition State). ALWAYS positive. A lower means a faster reaction.
Transition State (Activated Complex)
The unstable arrangement of atoms at the very peak of the energy profile. Here, old bonds are halfway broken and new bonds are halfway formed.
Putting it into Practice
Catalysts and Activation Energy
Paper 2 StyleHow would the addition of a catalyst affect the Exothermic Energy Profile shown above?
A catalyst provides an alternative reaction pathway with a lower activation energy.
- The 'hump' (Activation Energy barrier) would be lower.
- The starting energy of Reactants stays the SAME.
- The final energy of Products stays the SAME.
- Therefore, remains unchanged! Just the path is easier.
Practice: Defining Terms
Define the term Activation Energy ().