Chemical Nature of Reactants

• The chemical nature of a pure substance is what gives it its chemical properties.

  • For example: sodium is very reactive and oxidizes (loses electrons) quickly. With respect to sodium, iron has a slow oxidation reaction.

Concentration of Reactants

• Increasing the likelihood of 2 of the reactants colliding together and reacting.

Surface Area

• Surface area affects the ability of the reactants to come into contact with each other.

• Reactions are most often carried out in liquid solutions or in the gaseous phase, which have higher surface area.

Temperature

• Almost all chemical reactions occur faster at higher temperature.

  • Example – polaroid camera’s instant pictures develops quicker in warmer weather.

• Rate of the reaction tends to double with every increase of 10 oC.

Presence of a Catalyst

• Catalysts are chemical which speed up the rate of reaction but are not consumed by the reaction. There are two types:

  • Heterogenous catalysts: reactants and catalyst are in different physical states

    • Ex: production of polyethylene is sped up with a metal catalyst. An ethene molecule binds to the metal catalyst, breaking the double bond and allowing another ethene molecule to bond.

  • Homogeneous catalyst: reactants and catalyst are in the same physical state (aq or g)

    • Ex: biocatalysts or enzymes are in the aqueous state, as are most of their reactants. Lactose for example is an enzyme that helps in the digestion of milk.

Collision Theory

• Reactions occur when

  • Reactants collide with proper orientation

  • Reactants collide with enough kinetic energy

Activation Energy (Ea)

• Minimum energy of reactants for a reaction to occur

  • Overcome electrostatic force of repulsion

  • Break reactant bonds

  • The KINETIC energy of the collision must be GREATER than the POTENTIAL energy of the bonds