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Chapter 6, Lesson 4 Multimedia

Molecules Collide

Two molecules bounce off one another without reacting when they first collide. They collide again, and this time, they react.

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  • For molecules to react, they need to collide with enough energy.
  • If molecules hit with too little energy, they can just bounce off without reacting.
  • If they collide with enough energy, bonds can break and new bonds can form in a chemical reaction.


A small sample of ammonium dichromate is ignited using a wick. The flame starts a chemical reaction, in which the ammonium dichromate is converted into another product.

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  • The reactants just sit there until energy is added with the flame.
  • The added energy is enough to make molecules move fast enough to react.
  • The energy produced in the reaction is enough to keep the reactants breaking bonds and making new bonds. The demonstration shown in this video is very dangerous. Do not attempt to perform this demonstration.