1. How fast or slow is a reaction? And how can we make it go faster or slower?

2.  Rate is always dependent on time, the best example is how fast a car is going.  Chemical reaction rates are determined by the increase in products over time.  rate = ∆products/∆t, where ∆ = change  Because the products cannot form unless the reactants are consumed, rate is also equal to the decrease in reactants over time.  Rate = ∆reactants/∆t = ∆products/∆t

3.  Take the following reaction for example  H 2 + I 2  2 HI

4.  In order for a chemical reaction to occur, the molecules must collide and the collisions require a certain amount of energy. (see gas law simulator program)see gas law simulator program  Factors that affect frequency of collisions: Temperature – affects speed of molecules Pressure – affects distance between molecules Concentration – affects interference from molecules that do not participate in the reaction Surface area – affects area available for collisions to occur  Note that temperature, pressure, & surface area also affect the dissolving process.

5.  The greater the frequency of collisions and the greater the force of those collisions, the faster the reaction will occur.  Some reactions can take a billionth of a second, others hundreds of years.

7.  The energy needed for a collision to result in the formation of product(s)is called the “activation energy.” It is often abbreviated E a. Think of the activation energy as being the energy of the collision.

13.  A “catalyst” is a substance that increases reaction rate by lowering the required activation energy.  Catalysts are NOT consumed in the reaction; they can be used over and over again.  A biological catalyst is called a “enzyme,” and are present in all cells.