Chemistry2 Rates of Reaction xox

• chemical reactions only occur when reacting particles collide with sufficient energy
  
• ACTIVATION ENERGY = the minimum amount of energy needed by the particles to react

• the rate of reaction depends on 4 things: 
• 1) Temperature
• 2) Concentration/pressure    
• 3) Catalyst
• 4) Surface area

When the temp is increased:

• the particles gain heat energy
• therefore gaining kinetic energy
• so they move quicker
• and collide more frequently
• with greater energy
• so MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

In a solution, when the concentration increases:

• there are more particles
• which collide more frequently
• so MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

In a gas, when the pressure increases:

• the particles are closer together
• so they collide more frequently
• so MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

As the surface area increases:

• more particles are exposed/available for collisions
• so they collide more frequently
• meaning MORE SUCCESSFUL COLLISIONS

The rate of reaction also increases.

CATALYST = a substance which speeds up a reaction without being used up (or altered)    in the reaction

• reduces the activation energy
• so means more particles can collide successfully 
• so speeding up the reaction
• it provides a surface for the particles to attach to- increasing their chances of colliding 

Therefore the rate of reaction increases.

ADVANTAGES:

• reduces costs - can allow the reaction to work at a much lower temperature (reduces energy)
• reduces time - the rate of reaction is increased so more product produced quicker

DISADVANTAGES

• dif. reactions use dif. catalysts - e.g. manufacture of ammonia uses iron catalyst but hydrocarbons for example use broken pottery