Chemical Reaction Kinetics: Dissociation and Recombination of Diatomic Molecules (a 1-page exploration)
Interactive model, with minimal support
This Activity Requires:
Important! If you cannot launch anything from this database, please follow the step-by-step instructions on the software page.
Please Note: Many models are linked to directly from within the database. When an activity employs our scripting language, Pedagogica, as do some of the "guided" activities, the initial download may take several minutes. Subsequent activities will not take a long time. See this page for further instructions.
This model shows the dissociation and recombination of diatomic molecules. When the temperature rises, the diatomic bonds start to break, resulting in free radicals. When the temperature drops, the free radical starts to recombine and form diatomic bonds again. To provide the energy for dissociation and maintain the thermal stability of the recombined molecules, a heat bath is applied. This model can be used to explain a class of reactions, such as O2-->2O, H2-->2H.
Students will understand that:
The dissociation energy for a chemical bond is the amount of energy needed to fracture it;
Free radicals are formed in the process of chemical reactions.
A metaphor for students? Chemical reactions can be regarded as the processes of changing partners of atoms. A partnership between a pair of atoms is typically a covalent bond. The collision theory suggests that atoms bind with others, or lose partners, or swap partners, or do nothing when they collide.
Chemical reactions result from making and breaking chemical bonds. The number of each kind of atom in a reaction remains constant. There are two types of two-body elementary reactions: breaking and making a bond. The rule for breaking a bond is simple: a bond is broken only when enough energy is given to a bonded party for escaping the potential well formed by its binding partner.
Diatomic molecules that disassociate create free radicals. Free radicals react easily with molecules and other radicals.
Additional Related Concepts