Concentration and Reaction Rate
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
Raising a reactant's concentration usually raises a reaction's rate, since more particles per volume means more collisions between them.
Show
Phosphorus burns far more rapidly in pure oxygen than in ordinary air, where oxygen is only about a fifth of the gas present.
Watch for
"Usually" matters — exactly how rate responds to concentration is a separate, experimentally determined question, taken up next.