Rate of reaction - useful notes.

Rates of reaction

Affected by: 

Temperature;

Concentration;

Catalysts;

Surface Area.

Substances react by colliding with enough energy. 

• Large surface area - more collisions. 

• More collions = higher proportion of successful collisions, so the higher the rate of reaction.

Increasing temperature: 

• Particles have more kinetic energy.

• Particles move around faster.

• Collision occur more frequently and will be harder. Therfore more successful, increasing the rate of reaction. 

The higher the temperature, the faster the rate of reaction.

Increasing concentration:

• More particles in a volume (cm3) 

• Therefore, more collisions per second;

• The more collisions, the higher proportion of successful collisions; 

• So, rate of reaction increases.

Low concentration = few collisions 

High concentration = more collisions

A catalyst speeds up the rate of a chemical reaction, without being used up it's self. 

• Catalysts make chemical processes energy efficient - they can be re-used and so save the energy that would used to create high temperatures.

How do they work?

• Catalysts aDsorb (attatches) the reactants onto their surface, therefore making them more likely to react. 
• For collisions to be successful, they must occur with enough energy. This is known as the ACTIVATION ENERGY
• Catalysts work by lowering the activation energy.

There are two ways to measure 'Rates of Reactions': 

• Measure the rate at which a reactant is used up.

• Measure the rate at which a product is formed.

Things to measure:

• The mass of a substance.

• The volume of a gas is usually measured with a gas syringe, or sometimes an upside-down measuring cylinder or burette.