Darwinism designates a distinctive form of evolutionary explanation for the history and diversity of life on earth. Its original formulation is provided in the first edition of On the Origin of Species in 1859.
The enthalpy - or internal energy - of a substance is a function of its temperature and pressure. The change in internal energy with respect to change in temperature at fixed pressure is the Specific Heat at constant pressure - cp.
The potential energy (enthalpy) diagram for an exothermic reaction is shown below: The activation energy [Activation energy: The minimum energy required for a collision between particles, in order for a reaction to occur. ] (E a) for the forward reaction is shown by (A): E a (forward) = H (activated complex) - H (reactants) = 200 - 150 = 50 kJ mol-1