Place bags on fireproof surface and touch each with glowing cigarette or splint. Can be related to signs in hospitals where oxygen is being administered to avoid sources of ignition. Place another tablespoon of flour in wide end of funnel, lift above your head, and hold a lighted match about a foot above the funnel while blowing into tube. Can be related to explosions in grain elevators, using twigs to start campfires. Describe other situations involving the above variables and ask students to predict effect on the reaction rate.
Extra credit is given for students coming up with their own examples.
This experiment provides a phenomenological way to demonstrate factors that affect the rates of chemical reaction with readily available materials.