Reaction Rates and Collision Theory Notes

Definition = A process where one set of chemical substances is transformed to another set of chemical substances

• The transformation happens through the rearrangement of atoms

• A reaction is accompanied by an energy change

In a chemical reaction, matter is neither created nor destroyed

• For example, if we start out with four oxygen atoms, we need to end up with four oxygen atoms

• We say that matter is conserved

•The mass of matter is always the same before and after a chemical reaction.

•Energy is also conserved in a chemical reaction

• There is always energy stored within

chemical bonds

• It is called chemical potential energy

•Chemical energy is observed only when a chemical reaction occurs

• During a chemical reaction, energy is either absorbed or released

•A reaction that releases energy (usually in the form of heat) is called exothermic

•A reaction that absorbs energy (usually in the form of heat) is called endothermic

The speed at which reactants are used or products are formed (change in concentration).
Example: Formation of rust

Chemical reaction involves breaking bonds in reactants, rearranging atoms into products, and forming new bonds.
Particles must collide to react (not all collisions lead to a reaction).
Particles must have proper orientation.
Collision energy must be high enough to break old bonds (activation energy, $E_a$ ).

Temperature ( increased temperature = increased kinetic energy = molecules move faster = collision occurs more frequently )
Concentration ( higher concentration = more chances of collision )
Surface area.
Catalyst ( something that speeds up a chemical reaction )