A reaction mechanism must also account for the order in which molecules react.

These reactions are believed to take place during warm-up of the ice on grains which releases the molecules to react.

A molecule of a catalyst may react several million times a minute.

Before the molecules react with the reagents, they should be prepared for the reactions.

Sometimes a molecule can react using either an S1 or an S2 mechanism.

These molecules often react so as to complete their octet.

The molecule may also react with surface atoms to change its chemical properties.

For bimolecular reactions, two molecules collide and react with each other.

In these cases molecules will react with each other most often in specific arrangements.

When two separate molecules react, the condensation is termed intermolecular.