Chapter 15 – Fast and slow chemistry

Chemical energy
The sum of potential energy and the sum of kinetic energy, chemical energy of a substance is called the heat content and the enthalpy.
These energies result from things such as * Attractions between electrons and protons * Repulsion of the nuclei * Repulsion of electrons * Movement of electrons * Vibrations and rotations of bonds

Chemical reactions
During chemical reactions, atoms of the reactants are rearranged in to products with different energy levels 1. Exothermic reactions * Total energy of the products are less than of the reactants * Energy is released as heat energy * The products are more stable than the reactants due to its lower energy level * Eg- combustion of ethanol 2. Endothermic reactions * Total energy of the products are higher than of the reactants * Energy is added and absorbed * The products are unstable than the reactants due to its higher energy level.
The energy absorbed or released in the reaction is the heat of the reaction thus the enthalpy

Enthalpy = H(products) – H(reactants)

Thermochemical equations
Shows the energy released or absorbed during a chemical reaction. * Process results in releasing energy (eg- combustion) will have a (-)ve enthalpy * Process resulting in absorbing ever (eg- photosynthesis) will have a (+)ve enthalpy

Activation energies
During a course of reactions * Bonds